UBC Theses and Dissertations

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UBC Theses and Dissertations

Simulation and preliminary study of low resolution PCM and DPCM picture transmission systems. Allan, Donald Peter 1971

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SIMULATION AND PRELIMINARY STUDY OF LOW RESOLUTION PCM AND DPCM PICTURE TRANSMISSION SYSTEMS by DONALD PETER ALLAN B . A . S c , U n i v e r s i t y o f B r i t i s h C o l u m b i a , 1968 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF APPLIED SCIENCE We a c c e p t t h i s t h e s i s as c o n f o r m i n g t o t h e r e q u i r e d s t a n d a r d R e s e a r c h S u p e r v i s o r . . . . Members o f Committee Head o f D e p a r t m e n t Members o f t h e D e p a r t m e n t o f E l e c t r i c a l E n g i n e e r i n g THE UNIVERSITY OF BRITISH COLUMBIA September, 1971 In p r e s e n t i n g t h i s t h e s i s in p a r t i a l f u l f i l m e n t o f the r e q u i r e m e n t s f o r an advanced deg ree a t t he U n i v e r s i t y o f B r i t i s h C o l u m b i a , I a g r e e t h a t t he L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r r e f e r e n c e and s t u d y . I f u r t h e r ag ree t h a t p e r m i s s i o n f o r e x t e n s i v e c o p y i n g o f t h i s t h e s i s f o r s c h o l a r l y pu rpo se s may be g r a n t e d by the Head o f my Pepa r tment o r by h i s r e p r e s e n t a t i v e s . I t i s u n d e r s t o o d t h a t c o p y i n g o r p u b l i c a t i o n o f t h i s t h e s i s f o r f i n a n c i a l g a i n s h a l l not be a l l o w e d w i t h o u t my w r i t t e n p e r m i s s i o n . Department o f E. I (L>C W \ -^oJ. Elrxg\ V A g ^ r I r\ The U n i v e r s i t y o f B r i t i s h Co l umb i a Vancouve r 8, Canada ABSTRACT A m o n o c h r o m a t i c image c a n be r e p r e s e n t e d by a r e a l f u n c t i o n f ( x , y , t ) o f two s p a t i a l v a r i a b l e s and t i m e . P i c t u r e t r a n s m i s s i o n r e s e a r c h i s d i r e c t e d a t f i n d i n g m ethods o f t r a n s m i t t i n g a f a c s i m i l e o f f ( x , y , t ) a t minimum c o s t w h i c h s t i l l s a t i s f i e s some q u a l i t y c r i t e r i a . The e n s e m b l e o f s o u r c e , f u n c t i o n s , and t h e m e a s u r e s o f c o s t and q u a l i t y a r e d e f i n e d by t h e a p p l i c a t i o n . F o r many a p p l i c a t i o n s , t h e s u b j e c t i v e q u a l i t y i s an i m p o r t a n t m e a s u r e o f p e r f o r m a n c e . G e n e r a l l y , i t i s d i f f i c u l t i f n o t i m p o s s i b l e t o f i n d a t r a c t a b l e a n a l y t i c r e l a t i o n s h i p b e t w e e n t h e s o u r c e a n d s y s t e m p a r a m e t e r s , and t h e s u b j e c t i v e q u a l i t y . T h u s , f o r p i c t u r e p r o c e s s i n g r e s e a r c h , e q u i p m e n t must be a v a i l a b l e ' f o r s i m u l a t i n g p r o p o s e d s y s t e m s so t h a t p i c t u r e s c a n be p r o d u c e d and e s t i m a t e s made o f t h e s u b j e c t i v e q u a l i t y . T h i s t h e s i s w i l l d e s c r i b e a s y s t e m w h i c h was d e v i s e d f o r s t u d y i n g low r e s o l u t i o n p i c t u r e t r a n s m i s s i o n s y s t e m s . The s y s t e m e m p l o y s an image d i s s e c t o r t o i n p u t p i c t u r e d a t a t o a PDP-9 c o m p u t e r . The d a t a c a n be s t o r e d on m a g n e t i c t a p e , p r o c e s s e d and t h e n d i s p l a y e d on a p i c t u r e o u t p u t d e v i c e w h i c h e m p l o y s a T e k t r o n i x 561 O s c i l l o s c o p e . A s e t o f g e n e r a l p u r p o s e p r o g r a m s was d e v e l o p e d f o r m a n i p u l a t i n g p i c t u r e d a t a u s i n g t h i s h a r d w a r e c o n f i g u r a t i o n . T h r e e t e s t p i c t u r e s were r e a d i n and p a r t i c u l a r p r o g r a m s w e r e w r i t t e n t o c a l c u l a t e some p i c t u r e s t a t i s t i c s . T h e s t a t i s t i c s i n c l u d e . s i g n a l h i s t o g r a m s , a u t o - c o v a r i a n c e f u n c t i o n s a n d , some r u n l e n g t h s t a t i s t i c s f o r t h e two l e v e l m a t e r i a l . T h e s e s t a t i s t i c s were t h e n u s e d as d e s i g n i n f o r m a t i o n f o r some s i m u l a t i o n p r o g r a m s . A p r o g r a m was w r i t t e n t o s i m u l a t e P u l s e Code M o d u l a t i o n (PCM) and D i f f e r e n t i a l P u l s e Code M o d u l a t i o n (DPCM) s y s t e m s i n o r d e r t o e v a l u a t e t h e s u b j e c t i v e e f f e c t o f c h a n n e l e r r o r s on p i c t u r e s t r a n s m i t t e d by PCM and DPCM. A n a t t e m p t was a l s o made t o d e v e l o p a s i m p l e t w o - d i m e n s i o n a l f i l t e r p r o g r a m t o r e d u c e t h e e f f e c t o f c h a n n e l n o i s e . S i n c e t h e c h a n n e l n o i s e i n t h e PCM and DPCM s y s t e m s p r o d u c e d two--d i m e n s i o n a l n o i s e s w h i c h were v e r y d i f f e r e n t i n a p p e a r a n c e , two f i l t e r i n g r o u t i n e s were n e c e s s a r y . S u b j e c t i v e r a t i n g t e s t s were c o n d u c t e d t o e v a l u a t e t h e f i l t e r e d a nd u n f i l t e r e d PCM a n d DPCM p i c t u r e s . F o r t h e u n f i l t e r e d s y s t e m s , t h e s e t e s t s i n d i c a t e t h a t f o r g o o d c h a n n e l s , t h e DPCM s y s t e m i s b e t t e r t h a n t h e PCM s y s t e m w h i l e f o r v e r y b a d c h a n n e l s , t h e p i c t u r e s p r o d u c e d b y t h e PCM s y s t e m a r e s u b j e c t i v e l y b e t t e r t h a n t h o s e o f a DPCM s y s t e m u s i n g t h e same number o f b i t s . I t was f o u n d a l s o t h a t t h e PCM f i l t e r p r o p o s e d , i m p r o v e d t h e n o i s y p i c t u r e s w h i l e t h e p r o p o s e d DPCM f i l t e r p r o d u c e d no i m p r o v e m e n t and e v e n l o w e r s t h e q u a l i t y o f some o f t h e p i c t u r e s . i i i TABLE OF CONTENTS Page I THESIS INTRODUCTION 1.1 I n t r o d u c t i o n 1 1.2 P r e v i o u s R e s e a r c h 3 1.3 S c o p e o f t h e T h e s i s . . . . . 5 I I PICTURE PROCESSING HARDWARE ' 2.1 I n t r o d u c t i o n 7 2.2 Image D i s s e c t o r Camera 9 2.2.1 Image D i s s e c t o r Tube O p e r a t i o n . . . . 9 2.2.2 Camera H a r d w a r e . . . . . . 11 2.2.3 Image D i s s e c t o r S i g n a l t o N o i s e R a t i o 13 2.3 D i s p l a y H ardware f o r t h e 561 O s c i l l o s c o p e 16 2.3.1 I n t r o d u c t i o n 16 2.3.2 P o s i t i o n i n g t h e S p o t 18 2.3.3 E x p o s u r e C o n t r o l .. 21 2.3.4 D i s p l a y Summary 25 I I I PICTURE PROCESSING SYSTEM SOFTWARE 3.1 I n t r o d u c t i o n 27 3.2 Hardware C h e c k o u t P r o g r a m s 27 3.2.1 Camera P r o g r a m s 2 7 . 3.2.2 D i s p l a y P r o g r a m s 29 3.3 P r o c e s s i n g S o f t w a r e 31 3.3.1 I n t r o d u c t i o n 31 3.3.2 D a t a I n p u t P r o g r a m IMAGE 33 3.3.3 P r o c e s s i n g R o u t i n e s 35 3.3.4 The D i s p l a y P r o g r a m . . . . 43 i v Page 3.4 L i b r a r y P r o g r a m s . . 44 3.5 C o n c l u s i o n 47 IV S T A T I S T I C A L ANALYSIS OF PICTURE DATA 4.1 I n t r o d u c t i o n 48 4.2 S i g n a l H i s t o g r a m s 50 4.3 S i g n a l A u t o - C o v a r i a n c e F u n c t i o n s 53 4.4 Run L e n g t h S t a t i s t i c s 56 4.5 A L i n e D i s p l a y P r o g r a m . . . . 62 4.6 Summary.... 62 V DPCM AND PCM SIMULATION PROGRAMS, SUBJECTIVE TEST PROCEDURES AND RESULTS 5.1 I n t r o d u c t i o n 63 5.2 S i m u l a t i o n P r o g r a m s . . . . . 64 5.2.1 PCM and DPCM S i m u l a t i o n P r o g r a m SYSSIM 64 5.2.2 P i c t u r e S m o o t h i n g P r o g r a m s 71 5.2.3 DGRADE a S t a n d a r d P r o d u c i n g P r o g r a m 76 5*2.4 S i m u l a t i o n P r o g r a m Summary........ 78 5.3 S u b j e c t i v e T e s t P r o c e d u r e s 78 5.4 S u b j e c t i v e T e s t D a t a 79 .5.5 D a t a P r e s e n t a t i o n and R e s u l t s 84 5.6 S u b j e c t i v e T e s t Summary 89 APPENDIX A. DISPLAY COMMANDS AND CONNECTIONS 90 APPENDIX B. PCM AND DPCM TEST PICTURES....... 91 REFERENCES ... 97 V L I S T OF TABLES T a b l e Page I Camera C h e c k o u t P r o g r a m s . 28 I I D i s p l a y C h e c k o u t P r o g r a m s 29 I I I D a t a H a n d l i n g S y s t e m P r o g r a m s 33 IV F o r t r a n R o u t i n e s D e f i n e d by FPACK 41 V G e n e r a l P u r p o s e L i b r a r y R o u t i n e s 46 V I P i c t u r e F i l e s » 48 V I I P r o g r a m s f o r C a l c u l a t i n g P i c t u r e S t a t i s t i c s 48 V I I I Run L e n g t h S t a t i s t i c s P r o d u c e d by RLENGH... 58 IX P r o g r a m s t o P r o d u c e New P i c t u r e F i l e s 63 v i L I S T OF ILLUSTRATIONS F i g u r e • Pag< 1 B l o c k d i a g r a m o f a d i g i t a l p i c t u r e t r a n s m i s s i o n s y s t e m 2 2 F l o w c h a r t o f p i c t u r e p r o c e s s i n g r e s e a r c h 4 3 B l o c k d i a g r a m o f t h e co m p u t e r s i m u l a t i o n s y s t e m h a r d w a r e 8 4 C o n c e p t u a l d i a g r a m o f an image d i s s e c t o r t u b e . . . . 10 5 B l o c k d i a g r a m o f t h e image d i s s e c t o r c a m e r a a n d i t s i n t e r f a c e 12 6 A v e r a g e c a m era n o i s e power and q u a n t i z a t i o n n o i s e v e r s u s maximum s i g n a l a m p l i t u d e 17 7 B l o c k d i a g r a m o f t h e 561 d i s p l a y 19 8 I n t e n s i t i e s o f two p o i n t s on t h e CRT f a c e 23 9 D a t a f i l e f o r m a t 36 10 S i m p l i f i e d f l o w c h a r t i l l u s t r a t i n g t h e components o f a p r o c e s s i n g p r o g r a m 37 11 F l o w c h a r t o f p r o g r a m PROCES 38 12 S i m p l i f i e d f l o w c h a r t o f p r o g r a m PROCR 40 13 S i m p l i f i e d f l o w c h a r t o f p r o g r a m READ 45 14 P h o t o g r a p h s p r o d u c e d on t h e 561 f r o m d a t a i n t h e t h r e e p i c t u r e f i l e s 49 15 S i g n a l h i s t o g r a m o f f i l e HEATHER09 51 16 S i g n a l h i s t o g r a m o f f i l e SCHEMATC6. 51 17 S i g n a l h i s t o g r a m o f f i l e TEXTSPC06 52 18 A u t o - c o v a r i a n c e o f f i l e HEATHER09 . . . 54 v i i F i g u r e Page 19 A u t o - c o v a r i a n c e o f f i l e SCHEMATC6 54 20 A u t o - c o v a r i a n c e o f f i l e TEXTSPC06 55 21 E x p a n d e d d i s p l a y o f t h e a u t o - c o v a r i a n c e o f f i l e TEXTSPC06 55 22 N o r m a l i z e d a u t o - c o v a r i a n c e f u n c t i o n s f o r t h e t h r e e p i c t u r e f i l e s 57 23 Run l e n g t h h i s t o g r a m s f o r f i l e TEXTSPC06 60 24 Run l e n g t h h i s t o g r a m s f o r f i l e SCHEMATC6 61 25 B l o c k d i a g r a m s o f s y s t e m s s i m u l a t e d b y t h e p r o g r a m SYSSIM. 65 26 T r a n s i t i o n d i a g r a m f o r a b i n a r y s y m m e t r i c c h a n n e l 64 27 M e a n - s q u a r e s i g n a l t o me a n - s q u a r e e r r o r r a t i o o f a PCM s y s t e m 67 28 V a r i a t i o n o f s i g n a l t o n o i s e r a t i o w i t h a l p h a f o r a t h r e e b i t DPCM s y s t e m . 70 29 M e a n - s q u a r e s i g n a l t o m e a n - s q u a r e e r r o r r a t i o o f a DPCM s y s t e m 67 . 30 D a t a p o i n t s u s e d by t h e PCM f i l t e r t o smooth p o i n t X 72 . 31 D a t a p o i n t s u s e d by t h e DPCM f i l t e r t o smooth p o i n t X 74 . 32 F i l t e r a l g o r i t h m f o r t h e DPCM f i l t e r i n g r o u t i n e . . 75 33 S u b j e c t i v e SNR v e r s u s P f o r a PCM s y s t e m 81 34 S u b j e c t i v e SNR v e r s u s P f o r a DPCM s y s t e m 81 35 S u b j e c t i v e SNR v e r s u s P f o r a f i l t e r e d PCM s y s t e m 82 v i i i F i g u r e Page 36 S u b j e c t i v e SNR v e r s u s P f o r a f i l t e r e d DPCM s y s t e m 82 37 S u b j e c t i v e i s o - q u a l i t y l i n e s a nd l i n e s o f c o n s t a n t m e a n - s q u a r e e r r o r f o r a PCM s y s t e m 83 38 S u b j e c t i v e i s o - q u a l i t y l i n e s and l i n e s o f c o n s t a n t m e a n - s q u a r e e r r o r f o r a DPCM s y s t e m . . . . . 83 39 S u b j e c t i v e i s o - q u a l i t y l i n e s f o r t h e DPCM and PCM s y s t e m s 86 40 S u b j e c t i v e i s o - q u a l i t y l i n e s f o r t h e f i l t e r e d a n d u n f i l t e r e d PCM s y s t e m s 88 41 S u b j e c t i v e i s o - q u a l i t y l i n e s f o r t h e f i l t e r e d a n d u n f i l t e r e d DPCM s y s t e m s 88 i x ACKNOWLEDGEMENT I am g r a t e f u l t o t h e D e f e n c e R e s e a r c h B o a r d o f C a nada f o r s u p p o r t r e c e i v e d u n d e r g r a n t 66-2826 and f o r s u p p o r t r e c e i v e d f r o m t h e N a t i o n a l R e s e a r c h C o u n c i l o f C a n a d a . I w o u l d l i k e t o t h a n k my s u p e r v i s o r D r . R. W. D o n a l d s o n f o r h i s q u i d a n c e t h r o u g h o u t t h e p r o j e c t , D r . J . S M a c D o n a l d f o r a l l o w i n g me t o use h i s image d i s s e c t o r c a m e r a and Dr. G. B. A n d e r s o n f o r r e a d i n g a d r a f t o f t h i s t h e s i s and commenting. I w i s h t o a c k n o w l e d g e t h e a s s i s t a n c e p r o v i d e d by Mr. M i k e Koombes who d e s i g n e d and c o n s t r u c t e d t h e d i s p l e l e c t r o n i c s and Mr. H. B l a c k who p r o v i d e d a s s i s t a n c e d u r i n g t h e p r o j e c t and i n t h e p r e p a r a t i o n o f t h i s t h e s i s . I w i s h t o e x p r e s s my a p p r e c i a t i o n t o my mother f o r t y p i n g t h e f i n a l d r a f t o f t h i s t h e s i s and t o M e s s r s . K. A. S p e n c e r , G. A u s t i n , and J . Yan f o r many u s e f u l d i s c u s s i o n s . x 1 I . THESIS INTRODUCTION 1.1. I n t r o d u c t i o n A m o n o c h r o m a t i c image c a n be r e p r e s e n t e d as a r e a l f u n c t i o n ( f ( x , y , t ) ) o f t h r e e v a r i a b l e s , two s p a t i a l v a r i a b l e s , x a n d y , and t i m e t . The b a s i c p r o b l e m i n p i c t u r e c o m m u n i c a t i o n s y s t e m d e s i g n i s t o t r a n s m i t a f a c -s i m i l e f ( x , y , t ) o f t h e s o u r c e image f ( x , y , t ) w h i c h h a s 1 2 s a t i s f a c t o r y q u a l i t y a t minimum c o s t ~, . The e n s e m b l e o f s o u r c e f u n c t i o n s , t h e c o s t and t h e q u a l i t y m easure w i l l b e s p e c i f i e d by t h e a p p l i c a t i o n . I n s o u r c e c o d i n g o r b a n d w i d t h c o m p r e s s i o n r e s e a r c h , t h e c o s t i s t h e number o f b i t s r e q u i r e d t o e n c o d e t h e p i c t u r e a n d t h e q u a l i t y i s t h e s u b j e c t i v e q u a l i t y . I f o n l y d i g i t a l s y s t e m s a r e c o n s i d e r e d , t h e s y s t e m i s u s u a l l y r e p r e s e n t e d as shown i n f i g u r e 1. The s o u r c e e n c o d e r maps t h e s i g n a l f ( x , y , t ) i n t o a b i n a r y v e c t o r . The v e c t o r may be f u r t h e r e n c o d e d by t h e c h a n n e l e n c o d e r , t r a n s m i t t e d and d e c o d e d . V i e w i n g t h e s y s t e m i n t h i s way a l l o w s t h e p r o b l e m t o be s egmented. The c h a n n e l e n c o d i n g p r o b l e m i s common t o a l l d i g i t a l t r a n s -m i s s i o n schemes and h a s b e e n c o n s i d e r e d s e p a r a t e l y . The s o u r c e e n c o d i n g schemes w h i c h a r e d e p e n d e n t on t h e s o u r c e m a t e r i a l s a r e c o n s i d e r e d s e p a r a t e l y . P i c t u r e s o u r c e e n -c o d i n g schemes t r y t o t a k e a d v a n t a g e o f t h e s t r u c t u r e 3 o f t h e v i d e o s i g n a l B e c a u s e o f t h e d i f f i c u l t y o f c h a r a c t e r i z i n g t h e ) SOURCE / f(x.y.t) SOURCE CHANNEL / ' ENCODER ENCODER f(x.y.t) SOURCE CHANNEL DIGITAL DECODER DECODER CHANNEL F i g u r e - 1 B l o c k d i a g r a m o f a d i g i t a l p i c t u r e t r a n s m i s s i o n s y s t e m . 3 s o u r c e e n semble o f p i c t u r e s and t h e d i f f i c u l t y o f d e f i n -i n g an a n a l y t i c q u a l i t y m easure w h i c h a c c u r a t e l y r e l e c t s t h e s u b j e c t i v e q u a l i t y o f t h e image, p i c t u r e p r o c e s s i n g r e l i e s s t r o n g l y on e x p e r i m e n t a t i o n . P i c t u r e p r o c e s s i n g r e s e a r c h c o u l d be c o n s i d e r e d t o f o l l o w t h e f l o w c h a r t shown i n f i g u r e - 2. F o r t h e p u r p o s e s o f t h i s d i s c u s s i o n i t i s p o s s i b l e t o d i v i d e s o u r c e e n c o d i n g schemes i n t o two c l a s s e s . The f i r s t c l a s s i n c l u d e s f o r s i n g l e f r a m e e n c o d i n g t w o - d i m e n s i o n a l t e c h n i q u e s s u c h as t h e 4 5 6 Hadamard and F o u r i e r t r a n s f o r m s ' . The s e c o n d c l a s s c o n s i s t s o f o n e - d i m e n s i o n a l methods, where t h e two-d i m e n s i o n a l p i c t u r e f ( x , y , t ) i s f i r s t t r a n s f o r m e d i n t o a o n e - d i m e n s i o n a l s i g n a l ( v ( t ) ) u s i n g a s c a n n i n g o p e r a t i o n . O n e - d i m e n s i o n a l schemes t h e n t r y t o e f f i c i e n t l y e n c o d e t h e r e s u l t i n g t i m e s i g n a l . M o s t o p e r a t i o n a l p i c t u r e t r a n s m i s s i o n s y s t e m s a r e o f t h e o n e - d i m e n s i o n a l t y p e , and f u r t h e r d i s c u s s i o n s h a l l be r e s t r i c t e d t o t h a t t y p e o f s y s t e m . 1.2 P r e v i o u s R e s e a r c h P r e v i o u s w o r k e r s h a v e a n a l y z e d t h e p r o p e r t i e s o f t h e v i d e o s i g n a l v ( t ) d e r i v e d by s c a n n i n g t h e i n p u t 7 8 image f ( x , y , t ) ' . O t h e r s h a v e m e a s u r e d some p r o p e r t i e s o f t h e f u n c t i o n s f ( x , y , t ) and t h e v i d e o s i g n a l v ( t ) . 9 10 K r e t z m e r u s e d a n a l o g u e t e c h n i q u e s and O ' N e a l u s e d d i g i t a l t e c h n i q u e s t o m e a s u r e t h e p r o b a b i l i t y d e n s i t y f u n c t i o n ( p d f ) and a u t o - c o r r e l a t i o n f u n c t i o n o f f ( x , y ) ANALYTIC *5 H y p o t h e s i z e a M o d e l o f t h e P i c t u r e Random P r o c e s s C h e c k t h e M o d e l D e s i g n t h e S y s t e m w i t h A v a i l a b l e D a t a . O p t i m i z e W.R.T. some O b j e c t i v e M e a s u r e -< Change t h e S y s t e m EXPERIMENTAL M e a s u r e M a t e r i a l o f I n t e r e s t S i m u l a t e t h e O p e r a t i o n s t h e P r o p o s e d S y s t e m Would P r o d u c e C h e c k O b j e c t i v e M e a s u r e s . C h e c k R e s u l t s S u b j e c t i v e l y t o V e r i f y t h e P e r f o r m a n c e M e a s u r e F i g u r e -2 F l o w c h a r t o f p i c t u r e p r o c e s s i n g r e s e a r c h . 5 a n d v ( t ) r e s p e c t i v e l y . Run l e n g t h s t a t i s t i c s f o r v i d e o s i g n a l s d e r i v e d by s c a n n i n g two l e v e l images s u c h as t e x t 11 12 a n d l i n e d r a w i n g s h a v e a l s o b e e n m e a s u r e d and p u b l i s h e d ' 13 F r a n k p r o p o s e d a m o d e l f o r t h e random v i d e o p r o c e s s . Many w o r k e r s h a v e b e e n a c t i v e i n p r o p o s i n g and t e s t i n g p o s s i b l e s o u r c e e n c o d i n g schemes u s i n g s i m u l a t i o n R e s e a r c h h a s b e e n c o n d u c t e d on t h e e f f e c t s o f 17 18 19 22 n o i s e on t h e v i d e o s i g n a l ' ' ' , t h e r e l a t i o n s h i p b e t w e e n t h e v i d e o n o i s e and t h e r e s u l t i n g t w o - d i m e n s i o n a l 20 19 n o i s e i n t h e image ' , a n d t h e e f f e c t s o f two-21 d i m e n s i o n a l n o i s e . T h i s n o i s e r e s e a r c h r e s u l t e d i n t h e us e o f w e i g h t e d n o i s e s p e c t r u m as an o b j e c t i v e m e a s u r e 19 21 o f s y s t e m p e r f o r m a n c e ' . The a p p l i c a t i o n o f t h i s m e a s u r e t o o p t i m i z e t h e d e s i g n o f a s y s t e m has a l s o b e e n 23 r e p o r t e d 1.3 S c o p e o f t h e T h e s i s T h i s t h e s i s w i l l d e s c r i b e a s y s t e m w h i c h was d e v e l o p e d f o r s i m u l a t i n g t h e t r a n s m i s s i o n o f low r e s o l u t i o n p i c t u r e s , and w i l l d e s c r i b e some p r e l i m i n a r y r e s u l t s o b t a i n e d u s i n g t h i s s y s t e m . C h a p t e r I I d i s c u s s e s t h e h a r d w a r e w h i c h was u s e d t o i n p u t and o u t p u t p i c t u r e m a t e r i a l . C h a p t e r I I I e x p l a i n s t h e s y s t e m o f p r o g r a m s w h i c h were d e v e l o p e d t o e v a l u a t e t h e p i c t u r e i n p u t o u t p u t (I/O) e q u i p m e n t and t o f a c i l i t a t e t h e m a n i p u l a t i o n o f p i c t u r e d a t a . C h a p t e r IV b r i e f l y d e s c r i b e s s e v e r a l p r o g r a m s u s e d t o c a l c u l a t e p i c t u r e s t a t i s t i c s . R e s u l t s 6 o b t a i n e d when t h e s e p r o g r a m s were u s e d t o a n a l y z e t h r e e t e s t f i l e s a r e p r e s e n t e d and i n c l u d e s i g n a l h i s t o g r a m s , a u t o - c o v a r i a n c e f u n c t i o n s and some r u n l e n g t h s t a t i s t i c s . C h a p t e r V d e s c r i b e s t h e s i m u l a t i o n o f P u l s e Code M o d u l a t i o n . ( P C M ) and D i f f e r e n t i a l P u l s e Code M o d u l a t i o n (DPCM) s y s t e m s w i t h n o i s y c h a n n e l s , t h e s u b j e c t i v e t e s t p r o c e d u r e s u s e d t o r a t e t h e p i c t u r e s and t h e r e s u l t s o f t h e s u b j e c t i v e t e s t s . The s u b j e c t i v e t e s t s r e s u l t e d i n e a c h p i c t u r e , b e i n g a s s i g n e d an e q u i v a l e n t o r s u b j e c t i v e s i g n a l t o n o i s e r a t i o . The s u b j e c t i v e t e s t d a t a was p l o t t e d as s e t s o f i s o - q u a l i t y c u r v e s i n t h e (N,P) p l a n e , w here N i s t h e number o f b i t s p e r sample a n d P i s t h e b i t e r r o r p r o b a b i l i t y . T h e s e c u r v e s i n d i c a t e t h a t DPCM c h a n n e l n o i s e i s more a n n o y i n g t h a n PCM c h a n n e l n o i s e . 7 I I . PICTURE PROCESSING HARDWARE 2.1 I n t r o d u c t i o n T h i s c h a p t e r w i l l b r i e f l y d e s c r i b e s y s t e m h a r d w a r e an d t h e n d i s c u s s i n d e t a i l t h e p i c t u r e i n p u t a n d o u t p u t d e v i c e s . C omputer s i m u l a t i o n i s a w i d e l y u s e d t e c h n i q u e f o r p i c t u r e s y s t e m s i m u l a t i o n . Once s u i t a b l e i n p u t and o u t p u t e q u i p m e n t i s c o n s t r u c t e d , t h e c o m p u t e r s i m u l a t i o n s y s t e m i s v e r y v e r s a t i l e and r e p r o d u c a b l e . However, t h e s i z e a n d s p e e d o f p r e s e n t day c o m p u t e r s l i m i t t h e t e c h n i q u e t o s i n g l e f r a m e s i m u l a t i o n . F o r r e a l t i m e s y s t e m s s p e c i a l h a r d w a r e must s t i l l be u s e d f o r 24 s i m u l a t i o n . However, s i n c e o n l y s i n g l e f r a m e s were b e i n g s t u d i e d , a c o m p u t e r s i m u l a t i o n was s a t i s f a c t o r y f o r t h i s i n v e s t i g a t i o n . The h a r d w a r e c o n f i g u r a t i o n u s e d i s shown i n f i g u r e - 3 . The c o m p u t e r e q u i p m e n t e m p l o y e d was a PDP-9 c o m p u t e r w i t h 16,000 words o f memory, e x t e n d e d a r i t h m e t i c e q u i p m e n t ( E A E ) , a t a p e c o n t r o l l e r and 3 d e c t a p e d r i v e s , a t y p e 30 g r a p h i c a l d i s p l a y w i t h l i g h t p e n , a t e l e t y p e 40 and a g e n e r a l p u r p o s e d i g i t a l i n t e r f a c e w h i c h c o m p r i s e s a 12 b i t a n a l o g u e t o d i g i t a l (A/D) c o n v e r t e r , two 12 b i t d i g i t a l t o a n a l o g u e (D/A) c o n v e r t e r s , s e v e r a l g e n e r a l p u r p o s e i n p u t a n d o u t p u t r e g i s t e r s , and s e v e r a l g e n e r a l p u r p o s e f l a g s and c o n t r o l p u l s e s . F o r p i c t u r e p r o c e s s i n g work t h i s s y s t e m was augmented by a p i c t u r e i n p u t d e v i c e , J " ~3~ TAPE "* UNITS 4 TAPE CONTROLLE TYPE 30 GRAPHIC DISPLAY AND LIGHT PEN PDP - 9 . COMPUTER. 16,000 WORD MEMORY EAE STANDARD COMPUTER EQUIPMENT GENERAL PURPOSE DIGITAL INTERFACE SOI 31 12 B I T D / \ • > L2 B I T A/D 7ft 6 B I T A/D & CONT.ROl LOG£DC I J DISPLAY V SHRONHITE F I L T E R 7fT~ X VIDEO CAMERA CAMERA AND INTERFACE I PICTURE INPUT AND OUTPUT | EQUIPMENT F i g u r e -3 B l o c k d i a g r a m o f t h e c o m p u t e r s i m u l a t i o n s y s t e m h a r d w a r e . oo an image d i s s e c t o r camera w i t h i n t e r f a c e and a p i c t u r e o u t p u t d e v i c e w h i c h was b a s e d on a 561 T e k t r o n i x O s c i l -l o s c o p e w i t h a p p r o p r i a t e c o n t r o l l i n g e l e c t r o n i c s . T h r e e p i c t u r e s were mounted i n t h e camera and a d i g i t i z e d v e r s i o n o f e a c h p i c t u r e was r e a d i n t o t h e c o m p u t e r f r o m t h e image d i s s e c t o r c a m e r a . T h i s raw d a t a c o n s i s t i n g o f s i x o r n i n e b i t s a m p l e s was w r i t t e n i n a f i l e on one o f t h e d e c t a p e u n i t s . The d a t a was t h e n u s e d as i n p u t f o r p r o c e s s i n g p r o g r a m s w h i c h r e a d t h e raw d a t a f r o m t a p e , p r o c e s s e d i t a n d w r o t e t h e p r o c e s s e d d a t a i n a f i l e on a n o t h e r t a p e u n i t . A d i s p l a y p r o g r a m c o u l d r e a d any o f t h e p i c t u r e f i l e s f r o m t h e t a p e and d i s p l a y them on t h e 561 o s c i l l o s c o p e where t h e y c o u l d be p h o t o g r a p h e d . 2.2 Image D i s s e c t o r Camera 2.2.1 Image D i s s e c t o r Tube O p e r a t i o n The o p e r a t i o n o f t h e image d i s s e c t o r camera ( f i g u r e -4) and i t s i n t e r f a c e has b e e n d e s c r i b e d i n a 28 p r e v i o u s t h e s i s . An image o f t h e i n p u t p i c t u r e i s f o c u s e d o n t o t h e p h o t o c a t h o d e o f t h e image d i s s e c t o r t u b e . E a c h p o i n t on t h e p h o t o c a t h o d e e m i t s a c u r r e n t w h i c h i s p r o p o r t i o n a l t o t h e i n t e n s i t y o f t h e l i g h t f a l l i n g on i t . E l e c t r o n s f r o m any p a r t i c u l a r p o i n t on t h e p h o t o c a t h o d e c a n be f o c u s e d o n t o t h e a p e r t u r e and am-p l i f i e d by t h e m u l t i p l i e r c i r c u i t t o p r o d u c e a c u r r e n t a t t h e o u t p u t o f t h e t u b e . T hus by c o n t r o l l i n g t h e d e -f l e c t i o n c u r r e n t s i t i s p o s s i b l e t o examine t h e c u r r e n t OPTICS LIGHT SOURCE INPUT PICTURE PHOTOCATHODE ( SENS I T I V I T Y S) APERTURE (AREA A) J 1^ ELECTRON MULTIPLIER DEFLECTION COILS F i g u r e - 4 C o n c e p t u a l d i a g r a m o f an image d i s s e c t o r t u b e . 11 f r o m any p o i n t on t h e p h o t o c a t h o d e and i n t u r n t h e i n t e n s i t y o f l i g h t a t any p o i n t on t h e p h o t o c a t h o d e . T h e r e a r e two s i g n i f i c a n t f e a t u r e s o f t h i s t u b e . F i r s t , t h e t u b e may o p e r a t e a t any s c a n r a t e . T h i s makes i t u s e f u l f o r c o m p u t e r i n p u t a p p l i c a t i o n s where a f i x e d s c a n r a t e may n o t be d e s i r a b l e . S e c o n d , image d i s s e c t o r t u b e s c a n be p r o d u c e d w h i c h h a v e e x c e l l e n t s p a t i a l r e s o l u t i o n by u s i n g a s m a l l a p e r t u r e . The t u b e s u f f e r s f r o m one s h o r t c o m i n g i n t h a t i t h a s a v e r y low s i g n a l t o n o i s e r a t i o . T h i s l i m i t a t i o n w i l l be c o n s i d e r e d l a t e r . 2 . 2 . 2 . Camera Hardware A b l o c k d i a g r a m o f t h e c o m p l e t e image d i s s e c t o r c a m e r a a n d i t s i n t e r f a c e i s shown i n f i g u r e -5. M e a s u r e -ments were made t o l o c a t e s o u r c e s o f e r r o r i n t h e s y s t e m a n d t o d e t e r m i n e t h e camera t u b e ' s s i g n a l t o n o i s e r a t i o (SNR). The f i r s t s o u r c e o f e r r o r f o u n d w a s . t h e p o o r d e s i g n o f t h e v i d e o p r e - a m p l i f i e r w h i c h c a u s e d any n o i s e o n t h e power s u p p l y l i n e s t o a p p e a r a m p l i f i e d a t t h e o u t p u t o f t h e a m p l i f i e r . T h i s p r o b l e m was c o r r e c t e d by r e p l a c i n g t h e p r e - a m p l i f i e r w i t h a NEXUS a m p l i f i e r . The s e c o n d d e f e c t f o u n d was t h a t t h e v a l u e o f i n t e n s i t y r e a d i n t o t h e c o m p u t e r w o u l d c h a n g e w i t h t i m e . F u r t h e r t e s t i n g u n c o v e r e d two s o u r c e s o f t h i s d r i f t , t h e A/D c o n v e r t e r i n t h e camera i n t e r f a c e and t h e ch a n g e o f p h o t o c a t h o d e s e n s i t i v i t y due t o h e a t i n g o f t h e p h o t o c a t h o d e Camera I n t e r f a c e E l e c t r o n i c s C o n t r o l . L o g i c IS X D/A C o n v e r t e r f)/A C o n v e r t e r I 6 B i t A/D C o n v e r t e r / i d e o K h r o n h i t e Low P a s s F i l t e r Low P a s s F i l t e r X X D e f l e c t . Amp. Y D e f l e c t . Amp. Image D i s s e c t o r Tube V i d e o Pre-Amp. Power <£ S u p p l i e s Image D i s s e c t o r Camera I F i g u r e - 5 B l o c k d i a g r a m o f t h e image d i s s e c t o r c a m e r a a n d t h e c a m e r a i n t e r f a c e by. t h e l i g h t s o u r c e ' . The d r i f t was c o n t r o l l e d by u s i n g t h e 12 b i t A/D c o n v e r t e r i n t h e d i g i t a l i n t e r f a c e and o p e r a t i n g t h e camera w i t h a l e s s i n t e n s e l i g h t s o u r c e . Some o f t h e measurements were u s e d t o e s t i m a t e t h e f u n d a -m e n t a l l i m i t on t h e ca m e r a ' s p e r f o r m a n c e i m p o s e d by t h e t u b e ' s SNR. 2.2.3 Image D i s s e c t o r Camera S i g n a l t o N o i s e R a t i o C o n s i d e r t h e o u t p u t o f t h e camera when i t i s f o c u s e d on t h e p o i n t ( x , y ) . The s i g n a l a t t h e o u t p u t o f 27 t h e l o w p a s s f i l t e r V (x,y) i s s V _ ( x , y ) = S « I ( x , y ) - A - G - R - K (2-1) where I ( x , y ) = t h e i n t e n s i t y a t p o i n t (x,y) on t h e p h o t o c a t h o d e A = a r e a o f t h e d i s s e c t o r a p e r t u r e S = S e n s i t i v i t y o f t h e p h o t o c a t h o d e G = c u r r e n t g a i n o f t h e m u l t i p l i e r c i r c u i t K = v o l t a g e g a i n o f t h e v i d e o p r e - a m p l i f i e r R = t h e t u b e l o a d r e s i s t a n c e S'A'G*R i s f i x e d by t h e d e s i g n o f t h e t u b e and c h o i c e o f R. L e t Cx = S-A-G-R ( 2 - 2 ) , t h e n . V s ( x , y ) = C ^ K - K x j J (2-3) The s i g n a l f l u c u a t e s due t o t h e random n a t u r e o f t h e e l e c t r o n e m i s s i o n and m u l t i p l i c a t i o n p r o c e s s e s . The mean-2 s q u a r e v a l u e o f t h i s n o i s e o r f l u c t u a t i o n V i s g i v e n w 27 by . 14 V 2 '=• 2-k 2-S-I-A-W-G 2-R 2-K 2 (2-4) n where W = t h e b a n d w i d t h o f t h e low p a s s f i l t e r k = a f a c t o r a r i s i n g f r o m t h e random n a t u r e o f t h e s e c o n d a r y e m i s s i o n p r o c e s s L e t C 2 = 2 - k 2 - S - A - G 2 . R 2 ( 2 - 5 ) , t h e n V 2 = K 2-C 0-W-I (2-6) n z Thus f o r a p a r t i c u l a r v a l u e o f I t h e SNR i s g i v e n by 2 2 2 V K -C, - I C.. -V , 0 c N P _ s _ 1 _ 1 s (2-7) K -C.,-1 U 2 * W n 2 T h i s i s t h e SNR f o r a p a r t i c u l a r v a l u e o f V . I t i s n e c e s s a r y t o d e f i n e an a v e r a g e SNR f o r t h e w h o l e p i c t u r e , s SNR = — - £ — (2-8) V 2 n T o e v a l u a t e (2-8) i t was n e c e s s a r y t o assume a p r o b a b i l i t y d e n s i t y f u n c t i o n ( p d f ) f o r t h e s i g n a l V . The p d f was assumed t o be u n i f o r m and i s g i v e n by P V ( x ) = ^ m Vm > x 1 0 s = 0 0 > x > V m ~~2 2 2 2 V = C f - K - I V 3 (2-9) s i V 2 = K 2-C 0.W.I /2 (2-10) n 2 m From e q u a t i o n s ( 2 - 3 ) , (2-9) and (2-10) s u b s t i t u t e i n t o (2-8) t o e x p r e s s SNR i n t e r m s o f as 15 2 , 1 ; m S N R " I < F B J> i f < 2 - U ) From (2-11) i t c a n be s e e n t h a t t h e SNR c a n be i n c r e a s e d e i t h e r by i n c r e a s i n g o r by d e c r e a s i n g W. c a n n o t i n c r e a s e i n d e f i n i t e l y w i t h o u t t h e d a n g e r o f d a m a g i n g t h e t u b e . F o r t h e p r e - a m p l i f i e r g a i n u s e d i t was d e t e r -m i n e d t h a t an o u t p u t v o l t a g e o f 2.5 v o l t s i s t h e maximum a t w h i c h t h e t u b e c a n s a f e l y o p e r a t e . I t w o u l d a p p e a r t h a t t h e SNR c o u l d be r a i s e d i n d e f i n i t e l y by d e c r e a s i n g W. However, i f W i s d e c r e a s e d t o o much, t h e t i m e r e q u i r e d t o i n p u t a p i c t u r e w i l l become i m p r a c t i c a b l y l o n g and any r e d u c t i o n i n random n o i s e e r r o r s w i l l be masked by e r r o r s due t o d r i f t i n t h e s y s t e m . L e t B = (2-12) C l T h en f r o m ( 2 - 7 ) f o r a p a r t i c u l a r V s S N R = -I = B4 (2"13) n V 2 B = v - V (2"14) s M e a s u rements were made on t h e c a m e r a t o d e t e r m i n e t h e s i z e o f t h e f a c t o r B. I t was f o u n d t h a t B 2i 9-2 x 10" 7 ( v o l t s / H z ) (2-15) W i t h t h i s v a l u e o f B 16 SNR = V m ( 2 _ 1 6 ) 3(4.6x10 )W The n o i s e was p l o t t e d on a g r a p h ( f i g u r e - 6) w h i c h a l s o showed f o r c o m p a r i s o n t h e q u a n t i z i n g n o i s e p r o d u c e d by u n i f o r m q u a n t i z a t i o n t o v a r i o u s r e s o l u t i o n s . When a l l f a c t o r s were c o n s i d e r e d i t was d e c i d e d t o o p e r a t e t h e c a m e r a w i t h e q u a l t o 2.5 v o l t s and W e q u a l t o 200 Hz. W i t h t h i s o p e r a t i n g p o i n t t e n m i n u t e s a r e r e q u i r e d t o i n p u t a p i c t u r e c o n t a i n i n g 256x256 p o i n t s . I t c a n be s e e n f r o m t h e g r a p h i n f i g u r e - 6 t h a t t h e r e s u l t i n g SNR s h o u l d be s l i g h t l y b e t t e r t h a n f i v e b i t PCM. T h i s n o i s e l e v e l p l a c e s a l i m i t on t h e t y p e o f s y s t e m s w h i c h c a n be s i m u l a t e d as i t i s m e a n i n g f u l o n l y t o s i m u l a t e s y s t e m s whose SNR i s much l e s s t h a n t h a t o f t h e I/O e q u i p m e n t . Once t h e c a m e r a h a d b e e n c h e c k e d and m o d i f i e d as p r e v i o u s l y m e n t i o n e d , t h e p r o b l e m o f d e v e l o p i n g e q u i p m e n t t o p r o d u c e a p h o t o g r a p h i c o u t p u t f r o m t h e c o m p u t e r was a p p r o a c h e d . 2.3 D i s p l a y H ardware f o r t h e 561 O s c i l l o s c o p e D i s p l a y 2.3.1 I n t r o d u c t i o n To p r o d u c e d i g i t i z e d p i c t u r e s , e q u i p m e n t must be a v a i l a b l e w h i c h w i l l p r o d u c e a m a t r i x o f d o t s on f i l m whose p o s i t i o n and e x p o s u r e c a n be c o n t r o l l e d by t h e c o m p u t e r . I f s u c h e q u i p m e n t e x i s t s , d e s i r e d p i c t u r e s c a n b e p r o d u c e d by c h o s i n g t h e a p p r o p r i a t e d o t e x p o s u r e s and c o - o r d i n a t e s . A c a t h o d e r a y t u b e (CRT) i s a c o n v e n i e n t way o f r e a l i z i n g t h i s o b j e c t i v e s i n c e i t s s p o t p o s i t i o n and 17 1000 r-500 U 200 <N CO EH o > in o < EH O > W t/j H O D a w i 100 50 20 \-10 U 0.2 0.5 1.0 2.0 MAXIMUM SIGNAL AMPLITUDE (VOLTS) 5.0 F i g u r e - 6 Camera n o i s e power and q u a n t i z a t i o n n o i s e power v e r s u s maximum s i g n a l a m p l i t u d e . 18 i n t e n s i t y c a n be c o n t r o l l e d q u i c k l y and p r e c i s e l y . The d i s p l a y e q u i p m e n t . w h i c h was d e v e l o p e d i s shown i n f i g u r e - 7 2.3.2 P o s i t i o n i n g t h e S p o t The s p o t d e f l e c t i o n - v o l t a g e s a r e c o n t r o l l e d by two A n a l o g i c 12 b i t D/A c o n v e r t e r s . D a t a f o r t h e s e c o n v e r t e r s i s p l a c e d i n S t a n d a r d O u t p u t I n t e r f a c e (501) 31 and t h e n s t r o b e d i n t o b u f f e r r e g i s t e r s i n t h e r e s p e c t i v e . D/A c o n v e r t e r s . I f x and y a r e numbers i n t h e c o m p u t e r c c w h i c h r e p r e s e n t t h e x and y c o - o r d i n a t e s o f t h e d e s i r e d s p o t t h e n an i d e a l d i s p l a y w o u l d p r o d u c e a s p o t whose c o - o r d i n a t e s x , and y , a r e r e l a t e d t o x and y by d -*d c -*c •* e q u a t i o n s o f t h e f o r m x d = k 1 - x c + d 1 (2-17) ^ d = V^c + d 2 I t was f o u n d f o r t h e 561 o s c i l l o s c o p e f i n a l l y u s e d an d f o r s e v e r a l o t h e r CRT d i s p l a y s t e s t e d t h a t t h e a c t u a l r e l a t i o n s h i p s a r e more comp l e x f u n c t i o n s x d = f ( x c , y c , t ) (2-18) Y d = . g < x c , y c , t ) (2-19) where t h e f u n c t i o n s f a n d g d i f f e r enough f r o m t h e i d e a l c a s e (2-17) t o c a u s e p r o b l e m s . I n p i c t u r e o u t p u t h a r d -ware, where c l o s e l y s p a c e d p a r a l l e l l i n e s a r e b e i n g p r o d u c e d , t h e r e q u i r e m e n t s on e q u i p m e n t a r e v e r y s t r i n g e n t s i n c e an o b s e r v e r c a n e a s i l y d e t e c t l i n e s w h i c h a r e n o t i d e n t i c a l and p a r a l l e l . 19 T e c t r o n i x 561 O s c i l l o s c o p e C - 12 O s c i l l o s c o p e Camera H H o r z . V e r t . Amp. Amp. X D/A C o n v e r t e t r A \ \ y H a l f . n _< S i l v e r e d "\s~M-ir-r PMT Y D/A C o n v e r t e r SOI 31 \ Q X m o \ Q X O L i g h t E m i t t i n g D i o d e s 561 DISPLAY: E x p o s u r e C o n t r o l E l e c t r o n i c s >i m - H co G CD -P H J u CD CD Cn U rtf CD -P 4H Q) o « > I n t e r f a c e D/A 7> CO SOI 32 Cn rH fe cn cu 3 rH Cn (0 rH > I CO pq F l a g 56 DIGITAL INTERFACE CN CN rH O O O cn cn CN vc m LO . ,—^  CO X EH X EH CL, EH P O Q O X O rl H vA H w H F i g u r e - 7 B l o c k d i a g r a m o f t h e 561 d i s p l a y . C 7 U l CD a CD CO « o in EH O H fe CO 20 T h e r e a r e two p o s s i b l e a p p r o a c h e s t o t h e p r o b l e m . The f i r s t i s t o p u r c h a s e a h i g h q u a l i t y CRT d i s p l a y w h i c h s a t i s f i e s e q u a t i o n s ( 2 - 1 7 ) . T h i s a p p r o a c h c o u l d n o t be f o l l o w e d . The s e c o n d method i s t o d e t e r m i n e t h e f a c t o r s w h i c h c a u s e d f a n d g t o d i f f e r f r o m t h e i d e a l c a s e and r e d u c e t h e s e f a c t o r s t o t o l e r a b l e l e v e l s . A f t e r some i n v e s t i g a t i o n i t was f o u n d t h a t f m i g h t be a h y p o t h e t i c a l f u n c t i o n o f t h e f o r m . 2 x , = k , « x + k 0 ' X + k • s i n ( 2 i r - 6 0 t + 0) a l e 2 c 3 + k 4 - d ( t ) . + d± (2-20) 2 The f a c t o r k2'*-c r e p r e s e n t s t h e n o n - l i n e a r i t y w h i c h i s p r e s e n t i n t h e o s c i l l o s c o p e . The f a c t o r s w h i c h c a u s e d most p r o b l e m s were t h e t i m e v a r y i n g t e r m s . The s i n u s o i d a l t e r m r e p r e s e n t s s p o t w o b b l e due t o t h e p r e s e n c e . o f 60 Hz f i e l d s i n t h e v i c i n i t y o f t h e d i s p l a y . The f u n c t i o n d ( t ) r e p r e s e n t s d r i f t i n t h e s p o t p o s i t i o n w h i c h was e v i d e n t i f t h e d i s p l a y was c y c l e d on and o f f . The 60 Hz f i e l d s p r o d u c e d hum b a r p a t t e r n s w h i l e t h e s h o r t t e r m d r i f t c a u s e d s m a l l d i s c o n t i n u i t i e s on t h e p i c t u r e where w h o l e l i n e s were s h i f t e d by a c o u p l e o f p o i n t p o s i t i o n s . A f t e r much t e s t i n g i t was f o u n d t h a t t h e s e p r o b l e m s c o u l d be overcome by a c o m b i n a t i o n o f h a r d w a r e and p r o g r a m m i n g t e c h n i q u e s . To r e d u c e t h e hum p i c k u p , t h e c o o l i n g f a n o f t h e 561 s c o p e was d i s c o n n e c t e d and a l l s i g n a l l i n e s t o t h e o s c i l l o s c o p e were s h i e l d e d . I t was t h e n f o u n d t h a t i f t h e d i s p l a y p r o g r a m was s y n c h r o n i z e d w i t h t h e 21 60 Hz l i n e , and i f t h e h a r d w a r e and t h e p r o g r a m were s t r u c t u r e d so t h a t t h e sweep was s u f f i c i e n t l y f a s t , t h e n t h e hum w o u l d be i n v i s i b l e . To r e d u c e t h e e f f e c t o f t h e d r i f t , i t was f o u n d n e c e s s a r y t o r e q u i r e t h a t t h e d i s p l a y was n o t s t o p p e d d u r i n g t h e d i s p l a y o f a p i c t u r e . T h e s e r e q u i r e m e n t s p l a c e d s e v e r a l c o n s t r a i n t s on t h e d i s p l a y p r o g r a m w h i c h w i l l be d i s c u s s e d i n t h e n e x t c h a p t e r . 2.3.3 E x p o s u r e C o n t r o l Once methods h a d b e e n d e v i s e d t o p r o d u c e a g o od m a t r i x o f p o i n t s i t was n e c e s s a r y t o c o n t r o l t h e 29 p o i n t e x p o s u r e . The e x p o s u r e a t p o i n t ( x ^ , y ^ ) i s g i v e n by T E ( x f , y f ) = / I ( x f , y f , t ) d t (2-21) I f i t i s assumed t h a t I i s i n d e p e n d e n t o f t i m e t h e n E ( x f , y f ) = I ( x f , y f ) - T (2-22) I t c a n be s e e n t h a t t h e r e a r e two s i m p l e ways o f c o n t r o l l i n g t h e e x p o s u r e . E i t h e r , f i x T a n d v a r y I , o r f i x I and v a r y T. The s e c o n d method was c h o s e n s i n c e i t was e a s i e r t o i m p l e m e n t . I n i t i a l l y i t w o u l d a p p e a r t h a t t h i s t y p e o f c o n t r o l c o u l d be c o m p l e t e l y o pen l o o p t h u s n o t r e q u i r i n g any t y p e o f l i g h t s e n s o r . U n f o r t u n a t e l y , t h e i n t e n s i t y o f a s p o t on t h e CRT f a c e i s n o t a c o n s t a n t , i n d e p e n d e n t o f t h e s p o t p o s i t i o n . T h e s e i n t e n s i t y v a r i a t i o n s a r i s e due t o d i f f e r e n c e s i n e l e c t r o n p a t h g e o m e t r y t o d i f f e r e n t 22 p o i n t s on t h e s c r e e n a n d due t o g r a i n i n e s s and t h i c k n e s s v a r i a t i o n s o f t h e p h o s p h o r . T h e s e v a r i a t i o n s r e q u i r e d a l i g h t s e n s o r be c o n s t r u c t e d . I n a d d i t i o n t o c o n t r o l l i n g e x p o s u r e , a s t a b l e l i g h t s e n s o r p r o v i d e s an i n d i c a t o r f o r a d j u s t i n g t h e o s c i l l o s c o p e i n t e n s i t y t o p r e v e n t day t o day v a r i a t i o n s i n t h e p i c t u r e s . The s y s t e m w h i c h was d e v e l o p e d f u n c t i o n s a s f o l l o w s . A number p r o p o r t i o n a l t o t h e e x p o s u r e i s l o a d e d i n t o SOI 32. T h i s p r o d u c e s a v o l t a g e a t t h e o u t p u t o f an i n t e r f a c e D/A c o n v e r t e r , w h i c h i s s u p p l i e d t o t h e d i s p l a y e l e c t r o n i c s . When t h e i n t e n s i f y command i s g i v e n , t h e CRT i s u n b l a n k e d and t h e l i g h t f r o m t h e CRT s p o t i s p i c k e d up by a p h o t o m u l t i p l i e r t u b e (PMT). The PMT o u t p u t i s i n t e g r a t e d u n t i l t h e i n t e g r a l o f t h e p h o t o m u l t i p l i e r v o l t a g e e q u a l s t h e r e f e r e n c e v o l t a g e . When t h i s o c c u r s , t h e s p o t i s b l a n k e d a g a i n . I t c a n be s e e n t h a t t h e e x p o s u r e on t h e f i l m s h o u l d be p r o p o r t i o n a l t o t h e r e f e r e n c e v o l t a g e s u p p l i e d t o t h e d i s p l a y e l e c t r o n i c s . Once t h e t y p e o f c o n t r o l s y s t e m was c h o s e n i t was n e c e s s a r y t o c o n s i d e r what t y p e o f p h o s p h o r t o u s e and t h e p l a c e m e n t o f t h e p h o t o m u l t i p l i e r t u b e . Two p o i n t s on t h e s c r e e n w i t h s t e a d y s t a t e i n t e n s i t i e s o f 1^ and r e s p e c t i v e l y a r e t o h a v e i d e n t i c a l e x p o s u r e s ( f i g u r e - 8 ) T, °° E, = / i , ( t ) d t +• / i , ( t ) d t (2-23) 0 x T, 2 3 >-Z I I-2 12 -TIME F i g . 8 I n t e n s i t i e s o f two p o i n t s on t h e CRT f a c e . E l = I 1 ( T 1 + T ( e ~ T l / T " D ) + I 1 d - e ~ T l / T ) x ( 2 - 2 4 ) T CO E = / 2 i „ ( t ) d t + / i 9 ( t ) d t 0 T 2 ( 2 - 2 5 ) E 2 = I 2 ( T 2 + x ( e T 2 / T - 1 ) ) + I 2 ( 1 - e ~ T 2 / ' : ) T ( 2 - 2 6 ) The c i r c u i t r y e n s u r e s t h a t t h e f i r s t e x p o s u r e t e r m i s t h e same i n e a c h c a s e . E l = C l + " e T l / T ) T E 2 = C1 + I 2 ( l - e T 2 / T ) T ( 2 - 2 7 ) ( 2 - 2 8 ) Assume t h a t T^ > 5-x and T 2 > 5*T t h e n AE = E± - E 2 = T - A I I n g e n e r a l f r o m ( 2 - 2 4 ) E ^ = I^'T-L AE = T - A I _ T ,AI> E 1 - T y l v T^I^ ( 2 - 2 9 ) 24 From e q u a t i o n (2-29) i t c a n be s e e n t h a t a s h o r t p h o s p h o r time, c o n s t a n t r e d u c e s e r r o r due t o i n t e n s i t y v a r i a t i o n . A s h o r t t i m e c o n s t a n t a l s o a l l o w s f a s t e r o p e r a t i o n s i n c e i t i s n o t n e c e s s a r y t o w a i t f o r one s p o t t o d e c a y b e f o r e a n o t h e r s p o t i s s t a r t e d . A P-16 p h o s p h o r was c h o s e n w h i c h h a s . a t i m e c o n s t a n t o f l e s s t h a n 0.1 u s e e . S i n c e e x p o s u r e t i m e s were o f t h e o r d e r o f 100 u s e e . , e x p o s u r e v a r i a t i o n s due t o d i f f e r e n c e s i n i n t e n s i t i e s w i l l be r e d u c e d . To d e m o n s t r a t e t h e e f f e c t t h e p l a c e m e n t o f t h e PMT h a s on t h e f i e l d u n i f o r m i t y , c o n s i d e r a p o i n t w i t h d i s p l a y c o - o r d i n a t e s ( x d , y d ) w h i c h p r o d u c e s a s p o t on t h e f i l m a t t h e p o i n t ( x ^ , y ^ ) . The l i g h t f a l l i n g on (x ^ , y ^ ) w i l l be a f u n c t i o n o f ( x d , y d ) clue t o t n e v a r i a t i o n i n t h e l i g h t ' s p a t h l e n g t h and t h e s i z e o f t h e l e n s a p e r t u r e . I f t h i s v a r i a t i o n i s e x p r e s s e d by a f u n c t i o n T ^ ( x d , y d ) t h e n t h e f i l m e x p o s u r e w i l l be g i v e n by E f ( x f ' y f } = T f ( x d ' y d } * I ( x d ' y d ) ' T (2-30) However , w i t h t h e PMT, t h e i n t e n s i t y i s m e a s u r e d f r o m a n o t h e r p o s i t i o n and t h e r e w i l l g e n e r a l l y be a n o t h e r t r a n s m i t t a n c e f u n c t i o n T 4 C ( x ( j ' Y c j ) E t = T t ( x d , y d ) - I ( x d , y d ) . T (2-31) To p r o d u c e a u n i f o r m e x p o s u r e o v e r t h e e n t i r e d i s p l a y a r e a , w i l l be f i x e d and t h e e x p o s u r e t i m e T i s g i v e n by T = T t U d , y a ? . I ( x d , y a ) < 2- 3 2> 25 The f i l m e x p o s u r e t h e n becomes T f ( x ,y )-C . E f ( x f ' * f ' " T t ( x d , y d ) < 2- 3 3> Thus i t c a n be s e e n t h a t t h e e x p o s u r e w i l l be u n i f o r m o v e r t h e d i s p l a y a r e a o n l y i f t h e two t r a n s m i t t a n c e f u n c t i o n s T^ and T f c a r e r e l a t e d by a c o n s t a n t . T f = K « T t (2-34) When t h e d i s p l a y was i n i t i a l l y d e s i g n e d T^ was unknown and T^ was made c o n s t a n t by p l a c i n g t h e PMT a l o n g d i s t a n c e f r o m t h e CRT f a c e . I t l a t e r became e v i d e n t t h a t T^ i s n o t c o n s t a n t a n d some s h a d i n g i n t h e p h o t o g r a p h s was o b s e r v e d a n d a t t r i b u t e d t o t h i s c a u s e . I n a more p r e c i s e d e s i g n , t h i s f a c t o r w o u l d h a v e t o be c o n s i d e r e d . 2.3.4 D i s p l a y Summary A d i s p l a y was d e v e l o p e d b a s e d on a T e k t r o n i x 561 O s c i l l o s c o p e . The d i s p l a y e m p l o y e s a CRT w i t h a P-16 p h o s p h o r and some c o n t r o l e l e c t r o n i c s w h i c h c o m p r i s e two d e f l e c t i o n D/A c o n v e r t e r s and e x p o s u r e c o n t r o l e l e c t r o n i c s . Some d e s i g n c o n s i d e r a t i o n s c o n c e r n i n g t h e c h o i c e o f p h o s p h o r a n d t h e p o s i t i o n i n g o f t h e PMT were p r e s e n t e d . Due t o t h e o s c i l l o s c o p e h a v i n g some d e f e c t s i t was f o u n d n e c e s s a r y t o impose t h e f o l l o w i n g c o n s t r a i n t s on t h e d i s p l a y p r o g r a m . The d i s p l a y must be s y n c h r o n i z e d w i t h t h e 60 Hz. l i n e , t h e sweep s p e e d o f t h e d i s p l a y must be f a i r l y h i g h and t h e d i s p l a y must r u n c o n t i n u o u s l y u n t i l t h e p i c t u r e i s c o m p l e t e d . 26 The commands u s e d by t h e c o m p u t e r p r o g r a m s t o c o n t r o l t h e d i s p l a y a r e shown i n a p p e n d i x - A. D e v e l o p e d c o n -c u r r e n t l y w i t h t h e d i s p l a y was a s y s t e m o f p r o g r a m s f o r p r o c e s s i n g p i c t u r e d a t a and f o r e v a l u a t i n g and a d j u s t i n g t h e h a r d w a r e . 27 I I I . PICTURE PROCESSING SYSTEM SOFTWARE 3.1 I n t r o d u c t i o n I n t h e d e v e l o p m e n t o f t h e p i c t u r e p r o c e s s i n g s y s t e m , numerous p r o g r a m s were w r i t t e n . The p r o g r a m s w h i c h e v o l v e d c a n be p l a c e d i n t h r e e c a t a g o r i e s : (1) h a r d w a r e c h e c k o u t p r o g r a m s , w r i t t e n s p e c i f i c a l l y f o r t h e e v a l u a t i o n and a d j u s t m e n t o f t h e camera and d i s p l a y ; (2) d a t a m a n i p u l a t i o n p r o g r a m s , w h i c h a r e t h e c o r e o f t h e p i c t u r e p r o c e s s i n g s o f t w a r e s y s t e m a n d i n c l u d e p r o g r a m s f o r r e a d i n g , m a n i p u l a t i o n and d i s p l a y i n g p i c t u r e d a t a ; and (3) l i b r a r y p r o g r a m s , a s e t o f u t i l i t y p r o g r a m s w h i c h were w r i t t e n t o p e r f o r m t a s k s w h i c h o c c u r f r e q u e n t l y i n t h e o t h e r p r o g r a m s . The l i b r a r y p r o g r a m s i n c l u d e a random number p r o g r a m , and a g e n e r a l p u r p o s e g r a p h i c a l d i s p l a y p r o g r a m . 3.2 Hardware C h e c k o u t P r o g r a m s The h a r d w a r e p r o g r a m s c a n be s u b d i v i d e d i n t o camera c h e c k o u t and d i s p l a y c h e c k o u t p r o g r a m s . 3.2.1 Camera Prog r a m s A l l i n p u t f r o m t h e camera i s c o n t r o l l e d by a s u b r o u t i n e c a l l e d NPOINT. The c a l l i n g p r o g r a m s u p p l i e s t h i s s u b - p r o g r a m w i t h t h e c o - o r d i n a t e s o f t h e p o i n t t o be r e a d and t h e s u b r o u t i n e r e t u r n s w i t h t h e d a t a i n t h e a c c u m u l a t o r . The p r o g r a m i s v e r s a t i l e and a l l o w s t h e o p e r a t o r t o r e a d s i x b i t s a m p l e s f r o m t h e c a m e r a ' s own A/D c o n v e r t e r o r s i x o r n i n e b i t s a m p l e s f r o m t h e i n t e r f a c e 28 A/D c o n v e r t e r . I n a d d i t i o n , t h e p r o g r a m d e l a y c a n be v a r i e d s o t h a t t h e s u b r o u t i n e c a n o p e r a t e w i t h any l o w -p a s s f i l t e r b a n d w i d t h . T h r e e p r o g r a m s w h i c h u s e t h i s r o u t i n e a r e l i s t e d i n t a b l e - I . TABLE I . Camera C h e c k o u t P r o g r a m s  NAME FUNCTION NOISE To c o m p i l e a s i g n a l and n o i s e h i s t o g r a m w i t h d a t a a c q u i r e d by s c a n n i n g a 3600 p o i n t a r r a y 10 t i m e s . AERG To c h e c k t h e u n i f o r m i t y o f t h e l i g h t s o u r c e by m e a s u r i n g t h e a v e r a g e i n t e n s i t y i n 64 e q u a l a r e a s q u a r e s w h i c h p a r t i t i o n t h e image a r e a . L I NE A p r o g r a m f o r i n p u t i n g a l i n e o f d a t a f r o m t h e camera and d i s p l a y i n g i t on t h e t y p e 30 d i s p l a y . A l l t h e s e p r o g r a m s a r e l o a d e d w i t h a command d e c o d e r , w h i c h a l l o w s any p r o g r a m t o be r u n s i m p l y by t y p i n g a f i v e l e t t e r command on t h e t e l e t y p e . NOISE was t h e f i r s t camera c h e c k o u t p r o g r a m w r i t t e n . I t r e a d s and s t o r e s an a r r a y o f 3600 p o i n t s f r o m t h e camera. I t t h e n r e a d s t h e same a r r a y a g a i n , u p d a t e s a s i g n a l h i s t o g r a m , f i n d s t h e d i f f e r e n c e b e t w e e n t h e p r e s e n t v a l u e a n d t h e s t o r e d v a l u e o f e a c h s ample and s t o r e s t h i s d i f f e r e n c e v a l u e i n a n o i s e h i s t o g r a m . T h i s s e q u e n c e i s n o r m a l l y r e p e a t e d t e n t i m e s . A f t e r c o m p i l i n g t h e h i s t o g r a m s , t h e p r o g r a m c a n d i s p l a y t h e d a t a i n t h r e e ways. F i r s t , i t c a n o u t p u t on t h e t e l e -t y p e a t a b l e o f s i g n a l and n o i s e h i s t o g r a m v a l u e s . S e c o n d , t h e h i s t o g r a m s c a n be d i s p l a y e d on t h e t y p e 30 d i s p l a y . T h i r d , a s m a l l F o r t r a n s u b r o u t i n e c a n be u s e d t o c a l c u l a t e t h e s i g n a l mean and t h e n o i s e v a r i a n c e . T h i s p r o g r a m was u s e f u l f o r c h e c k i n g t h e n o i s e m a g n i t u d e and s i g n a l d r i f t when e v a l u a t i n g t h e s y s t e m and i s a l s o u s e d f o r a d j u s t i n g t h e l i g h t i n t e n s i t y when o p e r a t i n g . AERG i s a p r o g r a m f o r c h e c k i n g t h e u n i f o r m i t y o f t h e l i g h t s o u r c e . The p r o g r a m r e a d s t h e i n t e n s i t y a t 1024 p o i n t s i n e a c h o f 64 e q u a l s q u a r e s w h i c h c o m p l e t e l y c o v e r e d t h e image a r e a . The p r o g r a m t h e n p r i n t s a t a b l e o f t h e 64 a v e r a g e i n t e n s i t i e s f r o m w h i c h i t i s p o s s i b l e t o d e t e r m i n e t h e l i g h t d i s t r i b u t i o n . L I N E i s a p r o g r a m f o r r e a d i n g one h o r i z o n t a l l i n e o f d a t a and d i s p l a y i n g i t on t h e t y p e 30 d i s p l a y . I t i s u s e f u l f o r v e r i f y i n g t h a t t h e camera i s o p e r a t i n g c o r r e c t l y and i n p a r t i c u l a r i s u s e d f o r c h e c k i n g t h e c a m e r a f o c u s when a r a z o r b l a d e i s u s e d as t h e i n p u t i mage. 3.2.2 D i s p l a y P r o g r a m s The p r o g r a m s w h i c h were w r i t t e n f o r d i s p l a y c h e c k o u t a r e l i s t e d i n t a b l e I I . TABLE I I . D i s p l a y C h e c k o u t P r o g r a m s  NAME FUNCTION NEXPO To g e n e r a t e a t a b l e o f t e s t e x p o s u r e s and d i s p l a y t h e s e e x p o s u r e s w i t h t h e t y p e 30 d i s p l a y . 3 0 F A S T I To d i s p l a y t h e e x p o s u r e t a b l e f r o m NEXPO on t h ^ ' S G J - d i s p l a y u s y i g a d i s p l a y f o r m a t Of 256 p o i n t s o r 512 p o i n t s . NFRAME To d i s p l a y t h e o u t l i n e o f a s q u a r e on t h e 561 d i s p l a y f o r t h e p u r p o s e o f a d j u s t i n g t h e s i z e a nd p o s i t i o n o f t h e d i s p l a y image and t h e f o c u s o f t h e 561 o s c i l l o s c o p e . XTEST To g e n e r a t e a r a s t e r o f p o i n t s whose s c a n f o r m a t c a n be c h a n g e d and whose e x p o s u r e i s v a r y i n g s l o w l y w i t h t i m e f o r u s e i n c h e c k i n g and a d j u s t i n g t h e e x p o s u r e c o n t r o l h a r d w a r e a n d t h e 561 s p o t i n t e n s i t y . The f i r s t two p r o g r a m s NEXPO and F A S T I a r e u s e d f o r g e n e r a t i n g e x p o s u r e t e s t p a t t e r n s . T h e s e p a t t e r n s c o n s i s t o f e i t h e r e i g h t e q u a l v e r t i c a l b a r s w i t h d i f f e r e n t e x p o s u r e s o r 64 s q u a r e s o f e q u a l a r e a , b u t d i f f e r e n t e x p o s u r e s . The t e s t p a t t e r n s s e r v e two p u r p o s e s . F i r s t , t h e e x p o s u r e i s c h e c k e d a n d s e c o n d , t h e p a t t e r n s c a n be e x a m i n e d f o r d i s p l a y d e f e c t s s u c h as hum and d r i f t . NFRAME i s a s h o r t p r o g r a m w h i c h g e n e r a t e s a s q u a r e whose s i z e i s t h a t o f t h e p i c t u r e s t o be d i s p l a y e d . I t i s u s e d p r i m a r i l y f o r f o c u s i n g , p o s i t i o n i n g and a d j u s t -i n g t h e s i z e o f t h e image o f t h e 561 o s c i l l o s c o p e . To m a i n t a i n s i z e u n i f o r m i t y , t a p e m a r k e r s were p u t on t h e f a c e o f t h e s c o p e . A t t h e s t a r t o f e a c h new s e s s i o n t h e p r o g r a m NFRAME i s r u n and t h e s i z e a n d p o s i t i o n o f t h e image a r e a d j u s t e d u n t i l t h e s q u a r e i s a l i g n e d w i t h t h e s e m a r k i n g s . XTEST i s a p r o g r a m w h i c h g e n e r a t e s p o i n t s whose e x p o s u r e v a r i e s s l o w l y w i t h t i m e . By e x a m i n i n g v a r i o u s v o l t a g e s w i t h an o s c i l l o s c o p e , t h e o p e r a t i o n o f t h e e x p o s u r e e l e c t r o n i c s c a n be c h e c k e d and a d j u s t e d . 31 . T h i s p r o g r a m i s a l s o u s e d t o a d j u s t t h e 561 i n t e n s i t y . F o r t h i s t a s k an o s c i l l o s c o p e i s c o n n e c t e d t o t h e o u t p u t o f t h e p h o t o m u l t i p l i e r a m p l i f i e r . The l i g h t e m i t t i n g d i o d e s (LED) a r e t u r n e d on t o v e r i f y t h a t t h e PMT i s o p e r a t i n g and t h a t i t s g a i n i s c o r r e c t . The LEDs a r e t h e n t u r n e d o f f and t h e o s c i l l o s c o p e i n t e n s i t y i s t u r n e d up u n t i l i t r e a c h e s a s p e c i f i e d l e v e l . I t i s w o r t h n o t i n g t h a t a t t h e i n t e n s i t y l e v e l s u s e d f o r p h o t o g r a p h y , t h e s p o t i s a l m o s t i n v i s i b l e t o t h e e y e . The r e a s o n f o r o p e r a t i n g a t t h i s low l e v e l i s t o e n s u r e t h e s c r e e n i s n o t b u r n e d a n d t o p r e s e r v e t h e s p o t f o c u s w h i c h i s i n v e r s e l y p r o p o r t i o n a l t o t h e s p o t i n t e n s i t y . T h e s e t h r e e p r o g r a m s a r e u s e d t o c h e c k and a d j u s t t h e d i s p l a y and i t s p e r i p h e r a l e l e c t r o n i c s . I n a d d i t i o n t o t h e s e p r o g r a m s w h i c h a r e e s s e n t i a l f o r t h e o p e r a t i o n o f t h e h a r d w a r e i t was n e c e s s a r y t o w r i t e p r o g r a m s t o p r o c e s s p i c t u r e d a t a . The s e t o f p r o -grams w h i c h e v o l v e d a f t e r c o n s i d e r a b l e p r o g r a m m i n g e f f o r t a l l o w s t h e p r o c e s s i n g o f p i c t u r e d a t a q u i c k l y and e a s i l y . 3.3 P r o c e s s i n g S o f t w a r e 3.3.1 I n t r o d u c t i o n When c o n s i d e r i n g p r o c e s s i n g p i c t u r e a r r a y s on a s m a l l c o m p u t e r , s e v e r a l c h a r a c t e r i s t i c s o f t h e s m a l l c o m p u t e r must be k e p t i n m i n d . F i r s t , on a s m a l l c o m p u t e r , f l o a t i n g p o i n t a r i t h m e t i c i s more t h a n an o r d e r o f m a g n i t u d e s l o w e r t h a n f i x e d p o i n t a r i t h m e t i c . T h i s d i f f e r e n c e i s i m p o r t a n t f o r p i c t u r e p r o c e s s i n g o p e r a t i o n s w h i c h r e q u i r e e x t e n s i v e c a l c u l a t i o n s . T h u s , a l l t h e p r o c e s s i n g p r o g r a m s w r i t t e n , u s e f i x e d p o i n t a r i t h m e t i c . F i x e d p o i n t a r i t h m e t i c r e q u i r e s c a r e i n o r d e r t o r e d u c e r o u n d o f f e r r o r s b u t t h e e x e c u t i o n t i m e s a v i n g makes t h e s e e f f o r t s w o r t h w h i l e . S e c o n d , t h e c o r e memory o f a s m a l l c o m p u t e r i s t o o s m a l l t o h o l d a c o m p l e t e p i c t u r e 2 a r r a y . C o n s i d e r a s an example a 2 56 p o i n t p i c t u r e r e p r e s e n t e d by s i x b i t s a m p l e s w h i c h a r e p a c k e d t h r e e s a m p l e s p e r word. S u c h a p i c t u r e w o u l d r e q u i r e 21,844 words o f s t o r a g e w h i c h e x c e e d s t h e PDP-9 memory c a p a c i t y o f 16,000 w o r d s . T h i s s m a l l memory s i z e r e q u i r e s t h a t a b u l k s t o r a g e d e v i c e s u c h as a m a g n e t i c t a p e o r d i s k memory be u s e d . I n t h i s c a s e d e c t a p e i s u s e d as t h e b u l k s t o r a g e d e v i c e . The, s e q u e n t i a l n a t u r e o f a t a p e f i l e l e n d s i t s e l f t o s i m u l a t i n g s y s t e m s w h i c h a r e s e q u e n t i a l i n n a t u r e . S y s t e m s w h i c h t r a n s m i t a p i c t u r e by s c a n n i n g and t h e n t r a n s m i t t i n g t h e r e s u l t i n g v i d e o s i g n a l b y PCM o r DPCM a r e o f t h i s t y p e . I t w o u l d n o t , ho w e v e r , be e a s y t o s i m u l a t e some t w o - d i m e n s i o n a l schemes s u c h as t h o s e w h i c h employ t w o - d i m e n s i o n a l t r a n s f o r m s . A t h i r d m i n o r c o n s i d e r a t i o n i s t h a t s m a l l c o m p u t e r s do n o t h a v e a v a i l a b l e p o w e r f u l l i b r a r i e s o f m a t h e m a t i c a l r o u t i n e s w h i c h a r e a v a i l a b l e w i t h l a r g e c o m p u t i n g m a c h i n e s s u c h as an IBM 360-67. 3 3 The s o f t w a r e d e v e l o p e d a l l o w s t h e s i m u l a t i o n o f s e q u e n t i a l s y s t e m s s u c h as PCM and t w o - d i m e n s i o n a l o p e r a t i o n s w h i c h r e q u i r e d a t a f r o m up t o s i x t e e n c o n s e c u t i v e h o r i z o n t a l l i n e s . The s e t o f p r o c e s s i n g p r o g r a m s i s l i s t e d i n T a b l e I I I . TABLE I I I . D a t a H a n d l i n g S y s t e m P r o g r a m s NAME DATA DATA FUNCTION SOURCE DESTINATION _ _ _ _ _ IMAGE Camera D e c t a p e To i n p u t p i c t u r e f i l e s f r o m t h e cam e r a . PROCES D e c t a p e D e c t a p e To i n p u t d a t a f r o m t a p e t o s u p p l y i t t o p r o c e s s i n g s u b r o u t i n e s and t h e n t o t r a n s f e r p r o c e s s e d d a t a t o a new f i l e . PROCR D e c t a p e . D e c t a p e A more g e n e r a l p r o g r a m t h a n PROCES f o r u n -p a c k i n g d a t a f o r p r o c e s s i n g and f o r p a c k i n g and s t o r i n g t h e r e s u l t s . READT PHOTOR FPACK D e c t a p e PROCR F i l m PROCR To d i s p l a y a p i c t u r e on t h e 561 d i s p l a y f o r p h o t o g r a p h i n g . D e f i n e s a s e t o f F o r t r a n s u b r o u t i n e s so t h a t p i c t u r e d a t a c a n be p r o c e s s e d w i t h s u b r o u t i n e s w r i t t e n i n F o r t r a n . E a c h p r o g r a m w i l l be d e s c r i b e d i n more d e t a i l i n t h e f o l l o w i n g t e x t . 3 . 3 . 2 D a t a I n p u t P r o g r a m IMAGE IMAGE i s t h e p r o g r a m u s e d t o r e a d d a t a f r o m t h e c a m e r a a n d s t o r e i t on t a p e . The p r o g r a m u s e s t h e s u b -r o u t i n e NPO.INT t o i n p u t d a t a f r o m t h e c a m e r a . W i t h IMAGE t h e o p e r a t o r h as t h e c h o i c e o f A/D c o n v e r t e r s p r o v i d e d by NPOINT a n d t h e c h o i c e o f s t o r i n g s i x b i t d a t a s a m p l e s , p a c k e d t h r e e p e r word o r n i n e b i t s a m p l e s p a c k e d two p e r e i g h t e e n b i t word. A l s o he c a n c h o o s e t h e s c a n f o r m a t o f t h e p i c t u r e . I n o t h e r words he c a n s p e c i f y t h e number o f p o i n t s i n t h e x and y d i r e c t i o n s and t h e i r s p a c i n g . F o r t h e work t o be r e p o r t e d , p i c t u r e f i l e s c o n s i s t o f 2 256 p o i n t a r r a y s o f d a t a q u a n t i z e d t o s i x o r n i n e b i t s . The p i c t u r e d a t a i s s t o r e d on d e c t a p e . D e c t a p e as u s e d h e r e i s f o r m a t t e d i n t o 576 b l o c k s o f 256 w o r d s . I t was d e c i d e d t o u s e DEC s u p p l i e d t a p e h a n d l i n g p r o g r a m s a n d t o u s e t h e f i l e o r i e n t e d s o f t w a r e . When f i l e o r i e n t e d s o f t w a r e i s u s e d , e i g h t b l o c k s o f t h e t a p e a r e u s e d f o r a d i r e c t o r y w h i c h c o n t a i n s t a b l e s w h i c h i n c l u d e a n i n e c h a r a c t e r name f o r e a c h f i l e and t h e l o c a t i o n o f t h e f i l e on t a p e . A s i n g l e d e c t a p e c a n s t o r e f o u r n i n e b i t p i c t u r e s o r f i v e s i x b i t p i c t u r e s . When a u s e r l o a d s t h e image p r o g r a m he must s p e c i f y t o t h e p r o g r a m t h e l o c a t i o n and s i z e o f an a r e a o f c o r e memory w h i c h c a n be u s e d as a d a t a b u f f e r . When t h e u s e r h a s s p e c i f i e d t h e s c a n f o r m a t a n d t h e number o f b i t s p e r s a m p l e , t h e p r o g r a m c a l c u l a t e s t h e s i z e o f two d a t a b u f f e r s w h i c h a r e n e a r l y e q u a l i n s i z e t o e a c h o t h e r w h i c h h o l d i n t e g r a l numbers o f s c a n l i n e s a nd w h i c h w i l l f i t i n t o t h e b u f f e r a r e a a l l o w e d . The r e a s o n f o r s p l i t t i n g t h e b u f f e r a r e a i n two w i l l b e c o m e . e v i d e n t when t h e d i s -p l a y p r o g r a m i s c o n s i d e r e d . I n what f o l l o w s t h e s e two b u f f e r s a r e r e f e r r e d as B l and B2 r e s p e c t i v e l y . A p i c t u r e f i l e w i l l c o n s i s t o f a s e r i e s o f a l t e r n a t e segments com-p o s e d o f d a t a f i r s t f r o m b u f f e r B l and t h e n f r o m b u f f e r B2. The f i r s t segment i s p r e c e d e d by a h e a d e r a r e a w h i c h c o n t a i n s t h e s c a n p a r a m e t e r s . The o t h e r d a t a segments a r e s e p a r a t e d by s m a l l e r h e a d e r s w h i c h c o n t a i n some c o n t r o l d a t a . The l a s t segment i s a d j u s t e d t o i n c l u d e any l i n e s w h i c h do n o t f i t e x a c t l y i n t o b u f f e r s o f s i z e B l o r B2. The c o m p l e t e f i l e f o r m a t i s shown i n f i g u r e -9. The c h e c k -sum w i t h e a c h segment i s t h e modulo two sum o f a l l t h e d a t a i n t h a t b u f f e r . I t i s i n c l u d e d t o e n s u r e t h a t no d a t a e r r o r s a r e made by t h e t a p e d r i v e s . Once t h e d a t a i a w r i t t e n w i t h t h e d e s i r e d f o r m a t , i t c a n be p r o c e s s e d o r d i s p l a y e d . 3.3.3 P r o c e s s i n g R o u t i n e s Any p r o c e s s i n g p r o g r a m f o r t h i s s y s t e m w i l l h a v e t h e g e n e r a l s t r u c t u r e shown i n f i g u r e -10. I t c a n be s e e n t h a t e x c e p t f o r t h e a c t u a l p r o c e s s i n g s u b r o u t i n e , e a c h p r o c e s s i n g r o u t i n e has t h e same f o r m a t . Thus i t was d e c i d e d t o w r i t e a g e n e r a l p u r p o s e r o u t i n e w h i c h w o u l d h a n d l e t h e t a s k s w h i c h a r e common t o a l l p r o c e s s i n g , n a m ely, f e t c h i n g d a t a f o r p r o c e s s i n g and s t o r i n g p r o c e s s e d p i c t u r e f i l e s f o r d i s p l a y . Two s u c h p r o g r a m s were w r i t t e n . A s i m p l i f i e d f l o w c h a r t f o r t h e f i r s t r o u t i n e PROCES i s shown i n f i g u r e -11. T h i s p r o g r a m i s s u i t a b l e 36 -P -P CU g 0) H CU T J cu Checksum ^ No. words i n B l and h e a d e r No. d a t a l i n e s i n B l No. s a m p l e s p e r l i n e No. l i n e s i n a s c a n XO - i n i t i a l x c o - o r d i n a t e YO - i n i t i a l y c o - o r d i n a t e DX - x s p a c i n g o f p o i n t s DY - y s p a c i n g o f p o i n t s S i z e o f b u f f e r B l S i z e o f b u f f e r B2 No. o f l i n e s i n b u f f e r B l No. o f l i n e s i n b u f f e r B2 S i z e o f an odd b u f f e r D a t a b u f f e r B l -P c cu • o g o cn cu cu CO CO Checksum Nc. words i n B2 No: l i n e s i n t h i s b u f f e r No; s a m p l e s p e r l i n e D a t a b u f f e r B2 f -P C CU •p g co cn nJ cu in* co Checksum No. words i n odd b u f f e r No. l i n e s i n t h e b u f f e r No. s a m p l e s p e r l i n e Odd s i z e d d a t a b u f f e r F i g u r e - 9 D a t a f i l e f o r m a t it 37 I n i t i a l i z e t h e P r o g r a m Read D a t a f r o m Tape; S and Unpack i t P r o c e s s t h e D a t a P a c k t h e P r o c e s s e d D a t a and S t o r e i t on Tape No F i g u r e - 10 S i m p l i f i e d f l o w c h a r t i l l u s t r a t i n g t h e components o f a p r o c e s s i n g p r o g r a m . 38 G e t F i l e Name C l e a r W r i t e F l a g Y e s S e t W r i t e FLAG I n i t i a l i z e P r o c e s s S u b r o u t i n e ± Read a b u f f e r o f D a t a -> *~ Unpack a D a t a Sample No Pack and S t o r e t h e P r o c e s s e d D a t a W r i t e t h e b u f f e r o i P r o c e s s e d D a t a i f No 1 I n i t i a l i z e t h e R o u t i n e f o r P r o c e s s i n g P r o c e s s i n g S u b r o u t i n e t h e W r i t e F l a g i s s e t C l o s e t h e F i l e R e t u r n t o Command D e c o d e r F i g u r e - 11 F l o w c h a r t o f p r o g r a m PROCES f o r s i m u l a t i n g DPCM. o r PCM s y s t e m s . The u s e r t y p e s i n t h e name o f t h e p i c t u r e f i l e w h i c h i s t h e d a t a s o u r c e a n d i n d i c a t e s w h e t h e r a new f i l e o f p r o c e s s e d d a t a i s t o b e w r i t t e n . The p r o g r a m r e a d s a b u f f e r o f d a t a f r o m t h e f i l e , u n p a c k s t h e d a t a and e x i t s t o t h e p r o c e s s i n g s u b -r o u t i n e w i t h a s a mple v a l u e i n t h e a c c u m u l a t o r . On r e t u r n f r o m t h e s u b r o u t i n e , PROCES e x p e c t s t h e a c c u m u l a t o r t o c o n t a i n t h e o u t p u t o f t h e s i m u l a t e d s y s t e m . I f t h e u s e r h a s s p e c i f i e d a new f i l e , t h i s d a t a i s p a c k e d and w r i t t e n on t a p e . I f t h e u s e r h a s n o t s p e c i f i e d a new f i l e t h i s d a t a i s i g n o r e d . I n e i t h e r c a s e a n o t h e r d a t a v a l u e i s s u p p l i e d t o t h e p r o c e s s i n g s u b r o u t i n e u n t i l t h e i n p u t f i l e i s e x h a u s t e d . The mode o f o p e r a t i o n where no f i l e i s s p e c i f i e d i s u s e f u l f o r r o u t i n e s w h i c h c a l c u l a t e d s i g n a l s t a t i s t i c s . PROCES i s u s e f u l f o r s i m u l a t i n g s y s t e m s whose o u t p u t d e p e n d s on o n l y a s m a l l s e t o f p a s t and p r e s e n t i n p u t s i g n a l v a l u e s s u c h as t h e o u t p u t f r o m a PCM o r DPCM s y s t e m . . However, i t i s t o o r e s t r i c t i v e f o r s i m u l a t i n g t w o - d i m e n s i o n a l o p e r a t i o n s where t h e o u t p u t o f t e n d e p e n d s o n p a s t , p r e s e n t and f u t u r e l i n e s . To remove t h e s e r e s t r i c t i o n s a more g e n e r a l and c o m p l e x p r o g r a m c a l l e d PROCR was w r i t t e n . The p r o g r a m h a s t h e components shown i n f i g u r e -12. E a c h t i m e a p r o c e s s i n g s u b r o u t i n e e n t e r s r o u t i n e FETCH, i t i s r e t u r n e d w i t h a new d a t a v a l u e i n t h e a c c u m u l a t o r . E a c h t i m e a r o u t i n e c a l l s STORE w i t h a d a t a v a l u e i n t h e a c c u m u l a t o r , 40 PROCR I n i t i a l i z e G e t t h e I n p u t F i l e ' s Name S e t up P o i n t e r s and C o u n t e r s E x i t t o t h e p r o c e s s i n g R o u t i n e FETCH G e t ne*w d a t a Read d a t a From Tape Unpack i t and R E t u r n w i t h D a t a i n t h e A c c u m u l a t o r S t o r e STORE P a c k t h e D a t a and W r i t e i t on Tape - < — p r o c e s s e d D a t a C l o s e t h e O u t p u t F i l e V PROCESSING SUBROUTINE E x i t a t t h e u E n d o f P r o c e s s i n g F i g u r e -12 S i m p l i f i e d f l o w c h a r t o f p r o g r a m PROCR. t h i s v a l u e i s p a c k e d and w r i t t e n on t a p e . A p r o g r a m c a l l e d FPACK was w r i t t e n f o r u s e w i t h PROCR w h i c h d e f i n e s two F o r t r a n s u b r o u t i n e s and a f u n c t i o n s u b p r o g r a m . The F o r t r a n r o u t i n e s a r e l i s t e d i n t a b l e IV. TABLE IV. F o r t r a n R o u t i n e s D e f i n e d by FPACK  NAME FUNCTION F E T C H L ( I , N ) A s u b r o u t i n e t o r e a d N l i n e s o f d a t a i n t o t h e d a t a b u f f e r s t a r t i n g w i t h l i n e number I . I P I C T ( I , J ) F u n c t i o n s u b p r o g r a m w h i c h w i l l f e t c h t h e v a l u e o f t h e p i c t u r e f u n c t i o n a t row I , c o l u m n J , p r o v i d e d t h a t row I has b e e n r e a d i n t o t h e d a t a b u f f e r u s i n g t h e FETCHL s u b r o u t i n e . The f u n c t i o n d e f i n e d i s a F o r t r a n i n t e g e r v a r i a b l e . PACK(IV) :' A s u b r o u t i n e w h i c h p a c k s and s t o r e s a p r o c e s s e d p o i n t i n t h e o u t p u t f i l e . The o u t p u t v a l u e s must be p r e s e n t e d t o t h e PACK s u b r o u t i n e s e q u e n t i a l l y . The FETCHL r o u t i n e i s r e s t r i c t e d t o c a l l i n g l i n e s s e q u e n t i a l l y i n t o a d a t a b u f f e r . The l a s t s i x t e e n l i n e s c a l l e d a r e h e l d i n c o r e and a r e a c c e s s a b l e t o t h e p r o g r a m I P I C T . F o r t r a n ' s i n c r e a s e d e x e c u t i o n t i m e was f e l t t o be j u s t i f i e d i n v i e w o f t h e s i m p l i c i t y o f p r o g r a m m i n g . To i l l u s t r a t e t h e s i m p l i c i t y and power o f t h e s e r o u t i n e s c o n s i d e r t h e f o l l o w i n g e x a m p l e . Assume i t i s n e c e s s a r y t o r e p l a c e e a c h p i c t u r e p o i n t by an a v e r a g e o f i t s e l f a n d i t s e i g h t n e a r e s t n e i g h b o u r s . T h i s t a s k c o u l d be a c c o m p l i s h e d w i t h t h e f o l l o w i n g F o r t r a n s u b r o u t i n e . 42 ( n o t e - f o r t h i s example t h e e f f e c t o f t h e p i c t u r e e d g e s was i g n o r e d ) C C ENTER THE PROGRAM AND PRIME THE DATA BUFFER C SUBROUTINE F I L T E R CALL FETCHL (1,8) C C DO THE CALCULATION FOR A L L POINTS C DO 20 1=1,256 DO 30 J = l , 2 5 6 IV=0 DO 10 K=l,3 DO 10 L = l , 3 IV = I V + I P I C T ( I + K - 2 , J + L - 2 ) 10 CONTINUE IV = IV/9 C C STORE THE NEW OUTPUT C CALL PACK (IV) 30 CONTINUE C C GET A NEW LINE I F A L L DATA HAS NOT BEEN READ C LN= 1 + 8 IF(LN.GT.256) GO TO 20 CALL FETCHL (LN,1) 20 CONTINUE RETURN END One c a n s e e f r o m t h e example s u b r o u t i n e t h a t t h e F o r t r a n r o u t i n e s d e f i n e d by FRACK g r e a t l y s i m p l i f y t h e w r i t i n g o f d a t a p r o c e s s i n g s u b r o u t i n e s . B o t h PROCES a n d PROCR h a n d l e s i x a n d n i n e b i t f i l e s a nd w r i t e f i l e s whose f o r m a t i s i d e n t i c a l t o t h o s e w r i t t e n by IMAGE. Thus t h e o u t p u t f i l e s f r o m t h e p r o -c e s s i n g p r o g r a m s c a n be d i s p l a y e d o r u s e d as i n p u t f i l e s f o r f u r t h e r p r o c e s s i n g . 43 . 3.3.4 The D i s p l a y P r o g r a m A p r o g r a m f o r d i s p l a y i n g t h e p i c t u r e f i l e s i s t h e f i n a l d a t a h a n d l i n g p r o g r a m t o be c o n s i d e r e d . The d i s p l a y p r o g r a m was s u b j e c t t o s e v e r a l c o n s t r a i n t s w h i c h were m e n t i o n e d i n C h a p t e r I I . T h e s e were: t h e d i s p l a y must be s y n c h r o n i z e d w i t h t h e 60 c y c l e l i n e ; a h i g h s p e e d must be m a i n t a i n e d and t h e d i s p l a y must o p e r a t e c o n t i n u -o u s l y . The p r o g r a m f o r d i s p l a y i n g d a t a was s p l i t i n t o two p a r t s . The m a i n r o u t i n e c a l l e d READ r e a d s d a t a f r o m t a p e a n d s u p p l i e s i t t o t h e s e c o n d p a r t o f t h e p r o g r a m c a l l e d PHOTOR t h e a c t u a l d i s p l a y s u b r o u t i n e . The f i r s t two c o n s t r a i n t s were s a t i s f i e d e a s i l y . PHOTOR a c c u m u l a t e s a b u f f e r c o n t a i n i n g a c o m p l e t e l i n e o f p i c t u r e d a t a b e f o r e d i s p l a y i n g a n d t h e n u s e s t h e c o m p u t e r ' s r e a l t i m e c l o c k t o s y n c h r o n i z e w i t h t h e 60 Hz. l i n e . E a c h l i n e i s t h e n d i s p l a y e d s e v e r a l t i m e s q u i c k l y i n s u c c e s s i o n r a t h e r t h a n o n c e s l o w l y i n o r d e r t o m a i n t a i n a h i g h sweep s p e e d . The t h i r d c o n s t r a i n t , t h a t o f r u n n i n g t h e d i s p l a y c o n t i n u o u s l y was h a r d e r t o r e a l i z e . As s t a t e d e a r l i e r , i t i s i m p o s s i b l e t o s t o r e a c o m p l e t e p i c t u r e i n t h e c o m p u t e r ' s memory b e f o r e d i s p l a y i n g . Thus, i t was n e c e s s a r y t o i n t e r l e a v e t h e r e a d i n g o f d a t a f r o m t h e t a p e a n d t h e d i s p l a y o f d a t a . To a c c o m p l i s h t h i s i t was f i r s t n e c e s s a r y t o m o d i f y one o f t h e d e c t a p e h a n d l e r s (.DTD v e r s i o n B) i n o r d e r t h a t i t w o u l d a l l o w i n t e r l e a v i n g . 44 N e x t t h e p r o g r a m READ whose f l o w c h a r t i s shown i n f i g u r e -13 was w r i t t e n i n o r d e r t o i m p l e m e n t t h i s i n t e r l e a v i n g . Two b u f f e r s a r e s e t up i n c o r e . B e f o r e t h e d i s p l a y i s s t a r t e d , t h e f i r s t b u f f e r B l i s f i l l e d w i t h d a t a a n d t h e d a t a p o i n t e r s e t t o B l . The p r o g r a m t h e n s t a r t s d i s p l a y i n g d a t a f r o m b u f f e r B l and r e a d i n g f r o m d e c t a p e i n t o b u f f e r B2. When B l i s e x h a u s t e d , t h e p r o g r a m c h e c k s t o s e e i f B2 i s f u l l . When i t i s f u l l , t h e p r o g r a m swaps t h e r e a d and d a t a p o i n t e r s and d i s p l a y s d a t a f r o m b u f f e r B2 w h i l e r e a d i n g i n t o b u f f e r B l . The p r o g r a m c o n t i n u e s s w a p p i n g b u f f e r s i n t h i s f a s h i o n u n t i l t h e e n t i r e p i c t u r e h as b e e n d i s p l a y e d . The o u t p u t f o r m a t u s e d f o r a l l p i c t u r e s was 2 256 p o i n t s . The b o t t o m t w e l v e l i n e s o f t h e p i c t u r e were u s e d as an e i g h t l e v e l g r a y s c a l e i n o r d e r t o m a i n t a i n a c o n s t a n t c h e c k on t h e d i s p l a y o p e r a t i o n . A l l p i c t u r e s were t a k e n w i t h t y p e 47 P o l a r o i d f i l m . T h r e e t y p e s o f d a t a h a n d l i n g p r o g r a m s have b e e n d e s c r i b e d : t h e d a t a i n p u t p r o g r a m IMAGE; t h e d a t a p r o c e s s i n g r o u t i n e s PROCES and PROCR and t h e d a t a o u t p u t r o u t i n e s READ and PHOTOR. 3.4 L i b r a r y P r o g r a m s The l a s t g r o u p o f p r o g r a m s l i s t e d i n t a b l e V a r e t h e l i b r a r y p r o g r a m s w h i c h a r e u s e d by a l l t h e p r e v i o u s p r o g r a m s . READT I G e t t h e F i l e Name F i l l B l w i t h D a t a I n i t i a l i z e t h e D i s p l a y R o u t i n e S e t PDATA t o BI-PREAD t o BS D i s p l a y R o u t i n e PHOTOR I n i t i a l i z e D i s p l a y R o u t i n e PHOTOR R e t u r n t o Command D e c o d e r F i g u r e - 13 S i m p l i f i e d f l o w c h a r t o f p r o g r a m READ 46 TABLE V. G e n e r a l P u r p o s e L i b r a r y R o u t i n e s GRAPH FRAND INPUTR BUFOUT CORDR DTAPE D i s p l a y s a b u f f e r o f d a t a g r a p h i c a l l y on t h e t y p e 30 d i s p l a y . F e a t u r e s l i g h t p e n c o n t r o l f o r e x p a n d i n g and m o v i n g t h e d i s p l a y . U s es t h e p r o g r a m .LTA. R o u t i n e f o r g e n e r a t i n g random numbers w i t h a u n i f o r m p r o b a b i l i t y d i s t r i b u t i o n . G e n e r a l p u r p o s e o c t a l and d e c i m a l number i n p u t and o u t p u t r o u t i n e . R o u t i n e f o r p r i n t i n g a b u f f e r o f d a t a i n t a b u l a r f o r m on t h e t e l e t y p e . R e - e n t r a n t p r o g r a m f o r c a l c u l a t i n g c o -o r d i n a t e s o f a p o i n t i n a r a s t e r s c a n . S h o r t t a p e h a n d l i n g p r o g r a m works i n c o n j u n c t i o n w i t h Dec h a n d l e r s .DTA o r .DTD; s i m p l i f i e s t h e w r i t i n g , r e a d i n g , d e l e t i o n and r e n a m i n g o f p i c t u r e f i l e s . Two o f t h e p r o g r a m s FRAND a n d GRAPH a r e w o r t h y o f n o t e . FRAND i s a co p y o f t h e random number r o u t i n e 35 36 u s e d on t h e IBM 360 ' . I t employs t h e Lehmers m u l t i p l i c a t i v e c o n g r u e n c e method f o r g e n e r a t i n g a s e q u e n c e o f 17 b i t numbers w h i c h h a v e a u n i f o r m p r o b a b -. . . 32 l l i t y d e n s i t y f u n c t i o n and a p e r i o d o f 2 GRAPH i s a g e n e r a l p u r p o s e g r a p h i c a l d i s p l a y p r o g r a m w h i c h when u s e d i n c o n j u n c t i o n w i t h d i s p l a y h a n d l e r .LTA a l l o w s e i t h e r a l i n e a r o r s e m i - l o g r i t h m i c d i s p l a y o f a b u f f e r o f d a t a . GRAPH was u s e d e x t e n s i v e l y i n a l l t h e p r o c e s s i n g r o u t i n e s f o r c h e c k i n g t h e o p e r a t i o n o f t h e p r o g r a m s and f o r g a i n i n g i n s i g h t i n t o t h e o p e r a t i o n 47 o f t h e s i m u l a t e d s y s t e m s . T h i s p r o g r a m f e a t u r e s l i g h t p e n c o n t r o l f o r c o n t r o l l i n g t h e d i s p l a y . S e v e r a l e x a mples o f d i s p l a y s g e n e r a t e d u s i n g t h i s p r o g r a m w i l l be p r e s e n t e d i n t h e n e x t c h a p t e r . 3. 5 C o n c l u s i o n T h i s c h a p t e r h a s d e s c r i b e d g e n e r a l p u r p o s e p r o g r a m s w h i c h e v o l v e d f o r p i c t u r e p r o c e s s i n g and e q u i p m e n t d e v e l o p m e n t . T h e s e p r o g r a m s c o m p r i s e d h a r d w a r e c h e c k - o u t p r o g r a m s , d a t a h a n d l i n g p r o g r a m s and l i b r a r y p r o g r a m s . The n e x t c h a p t e r w i l l d e s c r i b e p a r t i c u a l a r r o u t i n e s w h i c h were e v o l v e d t o c a l c u l a t e s i g n a l s t a t i s -t i c s . R e s u l t s o b t a i n e d when t h e p r o g r a m s were a p p l i e d t o p i c t u r e f i l e s w i l l a l s o be p r e s e n t e d . 48 CHAPTER I V . S t a t i s t i c a l A n a l y s i s o f P i c t u r e D a t a 4.1 I n t r o d u c t i o n To t e s t t h e s y s t e m , t h r e e p i c t u r e s were r e a d i n t o t h e c o m p u t e r and s t o r e d on t a p e . The p i c t u r e s r e p r e s e n t e d t h e t y p e o f m a t e r i a l w h i c h m i g h t be t r a n s m i t -t e d on a f a c s i m i l e s y s t e m . They c o n s i s t o f a p i c t u r e o f a f a c e , a sample o f t e x t a nd a s e c t i o n f r o m a c i r c u i t s c h e m a t i c . The f i l e s a r e l i s t e d i n t a b l e V I . and d i s p l a y e d i n f i g u r e -14. The r e s u l t s t o be p r e s e n t e d i n t h i s c h a p t e r w i l l c o n s i s t o f t h e o u t p u t w h i c h r e s u l t e d f r o m a n a l y z i n g t h e s e t h r e e f i l e s . TABLE V I . P i c t u r e F i l e s F I L E NAME NO. BITS NO. POINTS TYPE OF MATERIAL HEATHER09 9 2 5 6 2 P i c t u r e o f a f a c e TEXTSPC06 6 2 5 6 2 P i c t u r e o f t e x t SCHEMATC6 6 2 5 6 2 P i c t u r e o f a s e c t i o n o f a s c h e m a t i c The p r o g r a m s w h i c h c a l c u l a t e d p i c t u r e s t a t i s t i c s f r o m t h e d a t a , o p e r a t e i n c o n j u n c t i o n w i t h t h e d a t a h a n d l i n g r o u t i n e PROCES a n d do n o t p r o d u c e any new p i c t u r e s , The r o u t i n e s a r e l i s t e d i n t a b l e V I I . TABLE V I I . P r o g r a m s f o r C a l c u l a t i n g P i c t u r e S t a t i s t i c s  NAME FUNCTION PHIS To c o m p i l e a s i g n a l v a l u e h i s t o g r a m DLINE To d i s p l a y a l i n e o f d a t a f r o m a p i c t u r e f i l e (a) HEATHER09 cle makes a number °««ook for the futi o f underground disti Wiur content of f u ^ N y haft or revei Pe cost of electricit L (b) TEXTSPC06 (c) SCHEMATC6 F i g u r e - 14 P h o t o g r a p h s p r o d u c e d o n t h e 561 f r o m d a t a i n t h e t h r e e p i c t u r e f i l e s . AUTO To c a l c u l a t e t h e a u t o - c o r r e l a t i o n f u n c t i o n o f a p i c t u r e f i l e . COVAR To c a l c u l a t e t h e a u t o - c o v a r i a n c e f u n c t i o n o f a p i c t u r e f i l e . RLENGH To c o m p i l e r u n l e n g t h h i s t o g r a m s and c a l c u l a t e some s t a t i s t i c s . 4.2 S i g n a l H i s t o g r a m s The p r o g r a m PHIS c o m p i l e s a s i g n a l h i s t o g r a m f r o m t h e p i c t u r e d a t a . The p r o g r a m s p l i t s t h e s i g n a l r a n g e i n t o 64 e q u a l p a r t s . A s i g n a l v a l u e w h i c h f a l l s w i t h i n one o f t h e s e 64 r a n g e s i s a s s i g n e d t o t h a t p a r -t i c u l a r r a n g e . F o r s i x b i t f i l e s t h e r e a r e o n l y 64 p o s s i b l e s i g n a l v a l u e s . T h e r e f o r e , e a c h s i g n a l v a l u e has i t s own r a n g e i n t h e h i s t o g r a m . F o r n i n e b i t f i l e s t h e r e a r e 512 p o s s i b l e s i g n a l v a l u e s . Thus e a c h h i s t o g r a m r a n g e c o n t a i n s e i g h t s i g n a l v a l u e s o r i n o t h e r w o r d s , o n l y t h e s i x most s i g n i f i c a n t b i t s a r e u s e d i n c o m p i l i n g t h e h i s t o g r a m o f a n i n e b i t f i l e . The p r o g r a m c a n o u t p u t t h e h i s t o g r a m i n t a b u l a r f o r m on t h e t e l e t y p e o r as a g r a p h on t h e t y p e 30 d i s p l a y by u s i n g t h e s u b r o u t i n e GRAPH. P h o t o g r a p h s o f h i s t o g r a m g r a p h s s h o w i n g l o g f r e q u e n c y p l o t t e d v e r s u s s i g n a l r a n g e a r e shown f o r t h e t h r e e d a t a f i l e s i n f i g u r e s 15,16 and 17. The h i s t o g r a m o f t h e f a c e f i l e i s f a i r l y u n i f o r m as w o u l d be e x p e c t e d . The h i s t o g r a m s o f t h e p i c t u r e o f t h e t e x t and s c h e m a t i c a r e more p e a k e d . The l o g r i t h m i c n a t u r e o f t h e d i s p l a y d e - e m p h a s i z e s t h e s h a r p n e s s o f t h e s e p e a k s . 51 i . . o m . . 4 . O . A . o « co o CM O rH : t 00 CN n vo rH o o cu H •rl m m 0 g u t n 0 -P 01 •H VD U rd £ C W t n a • H O co co VD H I CD M t n -H fe vo o co CN S3 O H CO O O CU rH •H V4H m o g rd 5H t n O 4J oi • •H G\ A 2 rH w rd W C! EH rj\< •H.pq co K in o i n o . . . A * o o o • • • ro CN rH ADN3n03H_ DOT o o CD SH d t n •H fe 4.0?" w a § 2.0 fe o Y-1 1.0 0.0 ••••••^••••••••^•••••••^••••••^•••••••••••••af •••••••••••••• 9 o. e • e 16. 0 32.0 48.0 64.0 SIGNAL RANGE F i g u r e - 17 S i g n a l h i s t o g r a m o f f i l e TEXTSPC06 53 4.3 S i g n a l A u t o - C o v a r i a n c e F u n c t i o n s The l a r g e s t s t a t i s t i c a l p r o g r a m s a r e t h e p r o g r a m s AUTO and a c l o s e l y r e l a t e d v a r i a t i o n COVAR w h i c h c a l c u l a t e t h e a u t o c o r r e l a t i o n and t h e c l o s e l y r e l a t e d a u t o - c o v a r i a n c e f u n c t i o n s r e s p e c t i v e l y . T h e r e t h e a u t o c o r r e l a t i o n (Rj) and a u t o - c o v a r i a n c e (C.) a r e d e f i n e d t o be 3 1 N R j = f ^ i - V j < 4-U C j = ^ ( J 1 x i - x i - j ) " ( X ) 2 ( 4~ 2> C j = ^ - ( x ) 2 (4-3) B o t h R and C a r e c a l c u l a t e d f o r j h a v i n g a r a n g e f r o m z e r o t o 255 o r one c o m p l e t e s c a n l i n e . I n e a c h c a s e N i s s u c h t h a t a l l d a t a was u s e d ; t h u s N i s a p p r o x i m a t e l y 65,000. B o t h p r o g r a m s c a n o u t p u t t h e n o r m a l i z e d f u n c t i o n s R J / R Q o r C . / C Q i n t a b u l a r f o r m on t h e t e l e t y p e o r as a g r a p h on t h e t y p e 30 d i s p l a y . The p h o t o g r a p h s o f t h e a u t o - c o v a r i a n c e f u n c t i o n s o b t a i n e d f o r t h e t h r e e p i c t u r e f i l e s a r e shown i n f i g u r e s 18,19 and 20. The c o r r e l a t i o n f u n c t i o n s a r e u s e f u l f o r e s t i m a t i n g t h e power s p e c t r u m o f t h e random p r o c e s s o f w h i c h t h e s e p i c t u r e s a r e sample f u n c t i o n s . The a u t o c o v a r i a n c e f u n c t i o n f o r t h e f a c e d e c a y s s l o w l y , i n d i c a t i n g t h e p r e s e n c e o f low f r e q u e n c i e s and h e n c e a low d e t a i l p i c t u r e . The i n c r e a s e i n t h e c e n t e r o f t h e g r a p h i s c a u s e d by t h e c o r r e l a t i o n b e t w e e n t h e l a r g e s i g n a l r e p r e s e n t i n g t h e l i g h t p a r t o f t h e u H o CJ I o EH D < Q W N 1.0 0.5 0.0 H-0.5 r o 2 •«...... 0 50 100 k m 8 8 « 150 200 DISTANCE F i g u r e - 18 A u t o - c o v a r i a n c e o f f i l e HEATHER09 1.0 w u H 0.5 > o u I o EH D *C Q W 0.0 3-0.5; O 3 .50. 100 6 « C 150 200 0 I DISTANCE F i g u r e 19 A u t o - c o v a r i a n c e o f f i l e SCHEMATC6 I l . o r 8 § 0.5-H o u go.Or •0.5-0 50 L • C C 100 . . . . I « . . . . 150 200 DISTANCE F i g u r e - 20 A u t o - c o v a r i a n c e o f f i l e TEXTSPC06 l . O r 0.5 0.0 -0.5 0 t a c e • 56 1 DISTANCE 100 F i g u r e - 21 E x p a n d e d d i s p l a y o f t h e a u t o - c o v a r i a n c e o f f i l e TEXTSPC06 56 f a c e a n d a l a r g e s i g n a l f r o m t h e b r i g h t b a c k g r o u n d . The a u t o - c o v a r i a n c e o f t h e f i l e SCHEMATC6 d e c a y s most q u i c k l y , i n d i c a t i n g t h a t i t was t h e m o s t d e t a i l e d p i c t u r e . A l l t h r e e f u n c t i o n s d i s p l a y a p e r i o d i c i t y w i t h a p e r i o d o f one s c a n l i n e l e n g t h w h i c h i s e x p e c t e d 13 f o r v i d e o s i g n a l s . F i g u r e -21 shows t h e l e f t h a l f o f t h e TEXTSPC06 a u t o - c o v a r i a n c e f u n c t i o n e x p a n d e d . The f i g u r e shows t h a t t h e f u n c t i o n has a p e r i o d i c r i p p l e s u p e r i m p o s e d on i t . T h i s r i p p l e was assumed t o be c a u s e d by t h e p e r i o d i c n a t u r e o f t h e t e x t p i c t u r e . A commonly assumed a u t o c o v a r i a n c e f u n c t i o n 13 f o r v i d e o i s g i v e n by P ( x ) = e ~ K l T ' (4-4) To t e s t t o s e e i f t h e s e f i l e s s u p p o r t e d t h i s a s s u m p t i o n , t h e t h r e e a u t o - c o v a r i a n c e f u n c t i o n s were p l o t t e d on s e m i - l o g r i t h m i c p a p e r i n f i g u r e -22. I t c a n be s e e n t h a t t h e c o v a r i a n c e f u n c t i o n o f t h e f i l e SCHEMATC6 a g r e e s w i t h t h e assumed f u n c t i o n b u t t h e o t h e r f u n c t i o n s a r e n o t i n c l o s e a g r e e m e n t a l t h o u g h t h e a g r e e m e n t i s n o t un-r e a s o n a b l e . The v a l u e s o f K f o r t h e two l i n e s i n 5 f i g u r e -21 a r e o,165 and 0.056. W i n t z o b t a i n e d a v a l u e o f K o f 0.090 f o r a p i c t u r e o f a f a c e and K i n t h e r a n g e o f o . l t o o.2 f o r more d e t a i l e d m a t e r i a l . 4.4 Run L e n g t h S t a t i s t i c s Run l e n g t h e n c o d i n g i s a method w h i c h has b e e n s u g g e s t e d f o r e n c o d i n g two l e v e l p i c t u r e s s u c h as t e x t 57 1.0 0.5 L ®' HEATHER09 1 3 SCHEMATC6 TEXTSPC06 W U o u 0.2 h 0.1 L o EH D < Q N 0.05 O 2 0.02 0.01 K = 0.056' F i g u r e - 22 N o r m a l i z e d a u t o - c o v a r i a n c e f u n c t i o n s f o r t h e t h r e e p i c t u r e f i l e s . 58 11 12 o r l i n e d r a w i n g s ' . I n o r d e r t o d e t e r m i n e t h e c o m p r e s s i o n p o s s i b l e by r u n l e n g t h e n c o d i n g , a p r o g r a m was w r i t t e n t o c o m p i l e r u n l e n g t h h i s t o g r a m s f o r t h e f i l e s c o n t a i n i n g t e x t and t h e s c h e m a t i c . The s i x b i t f i l e s c o n t a i n s i g n a l v a l u e s b e t w e e n z e r o and s i x t y -t h r e e . The p r o g r a m t r e a t s a l l s i g n a l s b e t w e e n z e r o and t h i r t y - o n e as z e r o and a l l s i g n a l s f r o m t h i r t y - t w o t o s i x t y - t h r e e a s o n e s . The p r o g r a m g e n e r a t e s s e v e r a l s t a t i s t i c s ( t a b l e V I I I ) s u c h as t r a n s i t i o n p r o b a b i l i t i e s w h i c h m i g h t be u s e f u l i n m o d e l l i n g t h e s o u r c e and s t a t i s t i c s w h i c h i n d i c a t e t h a t i t s h o u l d be p o s s i b l e t o o b t a i n a c o m p r e s s i o n o f a b o u t t h r e e by u s i n g r u n -l e n g t h e n c o d i n g . TABLE V I I I . R u n l e n g t h S t a t i s t i c s P r o d u c e d by RLENGH S t a t i s t i c F i l e F i l e TEXTSPCO 6 SCHEMATC6 A v e r a g e l e n g t h o f t h e b l a c k r u n s 5.43 4.44 A v e r a g e l e n g t h o f t h e w h i t e r u n s 18.4 24.7 E n t r o p y o f t h e b l a c k h i s t o g r a m 2.73 ( b i t s ) 3.00 ( b i t s ) E n t r o p y o f t h e w h i t e h i s t o g r a m 4.19 ( b i t s ) 5.44 ( b i t s ) E n t r o p y o f t h e c o m b i n e d h i s t o g r a m 3.90 ( b i t s ) 4.49 ( b i t s ) P(0) 0.225 0.152 P(D 0.775 0.848 P ( 0 I 0) 0.816 0.774 P ( l | 0) 0.184 0.226 P ( l | 1) 0.945 0.955 P ( 0 | 1) 0.055 0.045 Once t h e r u n l e n g t h h i s t o g r a m s a r e c o m p i l e d t h e p r o g r a m c a n o u t p u t them on t h e t e l e t y p e o r d i s p l a y them as a g r a p h on t h e t y p e 30 d i s p l a y . P i c t u r e s o f g r a p h s o b t a i n e d i n t h i s way a r e shown i n f i g u r e s 2 3 and 24. As e x p e c t e d , t h e a v e r a g e w h i t e r u n l e n g t h s a r e much l o n g e r t h a n t h e a v e r a g e b l a c k r u n l e n g t h s . The e n t r o p i e s shown i n t a b l e V I I I a r e c a l c u l a t e d i n t h e f o l l o w i n g manner. C o n s i d e r a p a r t i c u l a r h i s t o g r a m w h i c h c o n t a i n s d a t a on N r u n s w h i c h c a n h a v e l e n g t h s o f f r o m 1 t o m.. L e t n ( j ) be t h e number o f r u n s o f l e n g t h j . I n t h i s p r o g r a m m i s 256 w h i c h a p p e a r s t o be * s u f f i c i e n t l y l a r g e t o accommodate a l l t h e r u n s . H i s g i v e n by H = S 2liL-log2{2liI} ( b i t s ) (4-5) j = l The e n t r o p y i s c a l c u l a t e d t o p r o v i d e an i n d i c a t i o n o f t h e number o f b i t s w h i c h w o u l d be r e q u i r e d t o e n c o d e t h e r u n l e n g t h s i f some e f f i c i e n t c o d i n g were u s e d . The t h e o r e t i c a l c o m p r e s s i o n r a t i o d e p ends s t r o n g l y on t h e m a t e r i a l b e i n g t r a n s m i t t e d . R a t i o s v a r y -11 12 i n g f r o m f i v e t o s e v e n t e e n h a v e b e e n r e p o r t e d ' Some h a r d w a r e h a s b e e n r e p o r t e d w h i c h u s e d r u n l e n g t h e n c o d i n g on t h e w h i t e r u n s o n l y t o o b t a i n a d a t a com-5.Or 4. oi 3. Or u Z W a 2.C* fa o. a«.; 0.0 ft. • c t 50.0 100.0 o w D a fa o o 5.0 4.0 3.0 2.0 1.0* 0. 0 s» ...... 0.0 &, © a s RUN LENGTH (a) W h i t e F i g u r e - 23 Run l e n g t h h i s t o g r a m s f o r f i l e TEXTSPC06. 50.0 • **RUN LENGTH (b) B l a c k 100.0 CTl o 5. or 4.0 $j 3.0> w D a fa o o 2.0> l.Oj . 0.0; • 0.0 ft. 0 c c 50.0 *• RUN LENGTH (a) W h i t e 100.0 F i g u r e - 24 Run l e n g t h h i s t o g r a m s f o r 5.0 4 . o : 3 3.0 w a 3 fa o o 1-3 2;0 1. 0 0.0 0.0 50.0 ft. 0 8 6 © RUN LENGTH (b) B l a c k f i l e SCHEMATC6 p r e s s i o n o f f o u r .. The a c t u a l c o m p r e s s i o n o b t a i n e d i n p r a c t i c e may be much l o w e r t h a n t h e t h e o r e t i c a l s i n c e i t i s u s u a l l y n o t e c o n o m i c a l t o i m p l e m e n t h a r d w a r e w h i c h w o u l d a p p r o a c h t h e t h e o r e t i c a l p e r f o r m a n c e . 4.5 A L i n e D i s p l a y P r o g r a m DLINE i s a s h o r t p r o g r a m w h i c h d i s p l a y s a l i n e o f d a t a f r o m a p i c t u r e f i l e . The o p e r a t o r c a n i n p u t l i n e numbers f r o m t h e t e l e t y p e and t h e p r o g r a m w i l l r e a d t h e l i n e o f d a t a f r o m t a p e and d i s p l a y i t u s i n g t h e GRAPH s u b r o u t i n e . DLINE was u s e d p r i m a r i l y f o r c h e c k i n g on t h e o p e r a t i o n o f o t h e r d a t a p r o c e s s i n g p r o g r a m s . 4.6 Summary The p r o g r a m s j u s t d e s c r i b e d p r o v i d e d p i c t u r e s t a t i s t i c s w h i c h were u s e d i n d e s i g n i n g t h e s i m u l a t i o n p r o g r a m s and i n p r o v i d i n g i n s i g h t i n t o t h e n a t u r e o f t h e p i c t u r e m a t e r i a l . The p r o g r a m s i n C h a p t e r V, l i s t e d i n t a b l e IX, a r e d i f f e r e n t i n t h a t t h e y u s e d t h e i n p u t p i c t u r e d a t a t o p r o d u c e new p i c t u r e s . 63 CHAPTER V. DPCM and PCM S i m u l a t i o n P r o g r a m s  S u b j e c t i v e T e s t P r o c e d u r e s and R e s u l t s 5.1 I n t r o d u c t i o n T h i s c h a p t e r w i l l p r e s e n t a s t u d y made o f p i c t u r e d e g r a d a t i o n c a u s e d by c h a n n e l e r r o r s i n PCM and DPCM s y s t e m s . The c h a p t e r f i r s t d e s c r i b e s p r o g r a m s , T a b l e IX, u s e d t o p e r f o r m t h e f o l l o w i n g t h r e e f u n c t i o n s : (1) s i m u l a t i o n o f DPCM and PCM s y s t e m s w i t h n o i s y c h a n n e l s , (2) s m o o t h i n g t h e n o i s y p i c t u r e s t o r e d u c e t h e v i s i b i l i t y o f t h e c h a n n e l n o i s e and (3) p r e p a r a t i o n o f a s e t o f s t a n d a r d p i c t u r e s f o r use i n s u b j e c t i v e r a t i n g t e s t s . S e c o n d , t h e s u b j e c t i v e t e s t p r o c e d u r e s u s e d t o e s t i m a t e t h e s u b j e c t i v e q u a l i t y o f t h e n o i s y p i c t u r e s a r e d e s -c r i b e d . L a s t , t h e r e s u l t o f t h e s u b j e c t i v e t e s t s a r e p r e s e n t e d . TABLE IX. Pr o g r a m s t o P r o d u c e New P i c t u r e F i l e s  NAME FUNCTION SYSSIM To s i m u l a t e DPCM a n d PCM s y s t e m s . DGRAD To p r e p a r e p i c t u r e s w i t h s t a n d a r d i m p a i r -ments . F I L T E R A n o n - l i n e a r f i l t e r i n g p r o g r a m f o r s m o o t h i n g PCM P i c t u r e s . NLDPMF A n o n ^ l i n e a r f i l t e r i n g p r o g r a m f o r s m o o t h i n g DPCM p i c t u r e s . 64 5.2 S i m u l a t i o n P r o g r a m s 5.2.1 PCM a n d DPCM S i m u l a t i o n P r o g r a m SYSSIM I n o r d e r t o s i m u l a t e t h e p i c t u r e s w h i c h w o u l d be p r o d u c e d by PCM o r DPCM s y s t e m s w i t h n o i s y c h a n n e l s , a p r o g r a m c a l l e d SYSSIM was w r i t t e n w h i c h c o u l d s i m u l a t e e i t h e r o f t h e s y s t e m s shown i n f i g u r e -25. The p r o g r a m i s r e s t r i c t e d t o s i m u l a t i n g s y s t e m s w h i c h r e q u i r e up t o f i v e b i t s o f n o n - r e d u n d a n t c h a n n e l c o d i n g . F o r t h i s work i t was n o t n e c e s s a r y t o c o n s i d e r h i g h e r q u a l i t y s y s t e m s b e c a u s e o f t h e n o i s e l i m i t i m p o s e d by t h e c a m e r a . The p r o g r a m a l l o w s t h e a s s i g n m e n t o f any q u a n t i z e r c h a r a c t e r i s t i c and any n o n - r e d u n d a n t c h a n n e l c o d e t o r e p r e s e n t t h e q u a n t i z e r l e v e l s . The o n l y r e s t r i c t i o n on t h e q u a n t i z e r i s t h a t t h e DPCM q u a n t i z e r c h a r a c t e r i s t i c y= q ( z ) be an odd f u n c t i o n o f z. The n o i s y c h a n n e l m o d e l u s e d i s a b i n a r y s y m m e t r i c c h a n n e l BSC) w h i c h has a t r a n s i t i o n d i a g r a m as shown i n f i g u r e -2 6. F i g . 26 T r a n s i t i o n d i a g r a m f o r a b i n a r y s y m m e t r i c c h a n n e l Q u a n t i z e r y i C h a n n e l s. 1 B i n a r y r . 1 C h a n n e l E n c o d e r S y m m e t r i c C h a n n e l D e c o d e r (a) PCM s y s t e m w i t h a n o i s y c h a n n e l x. i a ^ i - i z. \ / Q u a n t i z e r . y i C h a n n e l E n c o d e r s. i B i n a r y S y m metric C h a n n e l r . I C h a n n e l D e c o d e r X a 9^ • + a (b) DPCM s y s t e m w i t h a n o i s y c h a n n e l F i g u r e - 2 ^ B l o c k d i a g r a m s o f s y s t e m s s i m u l a t e d by t h e p r o g r a m SYSSIM T h i s t y p e o f c h a n n e l c a n be c h a r a c t e r i z e d by one p a r a -m e t e r , t h e b i t e r r o r p r o b a b i l i t y P. The r e l a t i o n s h i p b e t w e e n P and p a r a m e t e r s o f some o t h e r c h a n n e l m o d e l s 31 ha s b e e n d i s c u s s e d by Yan F o r t h e PCM s y s t e m , t h e o p e r a t o r has t h e c h o i c e o f q u a n t i z e r c h a r a c t e r i s t i c i n c l u d i n g t h e number o f l e v e l s , t h e m a g n i t u d e o f a random number o r d i t h e r s i g n a l (d^) and t h e b i t e r r o r p r o b a b i l i t y P. I t was d e c i d e d t h a t s i n c e t h e p i c t u r e s i g n a l h i s t o g r a m o r p r o b a b i l i t y d e n s i t y f u n c t i o n was f a i r l y u n i f o r m , u n i f o r m 32 q u a n t i z a t i o n and n a t u r a l c o d i n g w o u l d be u s e d U s i n g t h a t c o n f i g u r a t i o n a s e t o f PCM p i c t u r e s was p r o d u c e d f r o m t h e f i l e HEATHER09 w i t h t h e number o f c h a n -n e l b i t s e q u a l t o 2,3 and 4 and t h e b i t e r r o r p r o b a b i l i t i e s o f 1 0 ~ 4 , 1 0 ~ 3 , 1 0 ~ 2 and 1 0 _ 1 . The b i t r a n g e o f two t o f o u r was c h o s e n b e c a u s e one b i t PCM w o u l d n o t be mean-i n g f u l and f i v e b i t PCM was t o o h i g h q u a l i t y f o r s i m u l a t i o n w i t h t h e a v a i l a b l e h a r d w a r e . The b i t e r r o r r a t e P was c h o s e n t o y i e l d a w i d e r a n g e o f p i c t u r e q u a l i t y f r o m -4 e s s e n t i a l l y e r r o r f r e e w i t h P e q u a l t o 10 t o v e r y n o i s y p i c t u r e s w i t h P e q u a l t o 10 \ F i g u r e -27 shows t h e m e a s u r e d i n b a n d SNR o b t a i n e d f o r t h e v a r i o u s PCM s y s t e m s . 30 F o r t h e DPCM s y s t e m t h e o p e r a t o r has c o n t r o l o v e r t h e q u a n t i z e r c h a r a c t e r i s t i c , t h e f e e d b a c k p a r a m e t e r a a n d t h e b i t e r r o r p r o b a b i l i t y P. 67 30,-~ 25 IB O 6 2 0 tc UI OT 6 15 z < z © 10 • 4 B ITS A 3 BITS e 2 BITS -I - 2 - 3 - 4 10 ' 10 - 10 " 10 BIT ERROR PROBABIL ITY P 10 10 -6 F i g u r e - 27 M e a n - s q u a r e s i g n a l t o me a n - s q u a r e e r r o r r a t i o o f a PCM s y s t e m . 35 30 25 m 2 20 cc o 1 3 < z o (0 10 A 4 BITS e 3 BITS o 2 BITS v I BITS _1_ 10"' 10 2 I 0 " 3 I 0 - 4 BIT E R R O R PROBAB IL ITY P 10 r 5 10 F i g u r e - 29 M e a n - s q u a r e s i g n a l t o mean-square e r r o r r a t i o o f a DPCM s y s t e m . 68 S i n c e t h e p r o b a b i l i t y d e n s i t y f u n c t i o n o r s i g n a l h i s t o g r a m o f t h e d i f f e r e n c e s i g n a l z^ i s s h a r p l y p e a k e d a r o u n d z e r o i t was d e c i d e d t o u s e a -n o n - u n i f o r m q u a n t i z e r w h i c h q u a n t i z e d s m a l l v a l u e s o f z more a c c u r a t e l y t h a n i t q u a n t i z e d l a r g e v a l u e s . The q u a n t i z e r c h o s e n was a l o g r i t h m i c q u a n t i z e r w h i c h f o l l o w e d t h e c o m p r e s s i o n law. V o u t - l o g (I + p ) " 1 ^ ' 1 + ^ ^ ' - - ' V i , , ) <5-l> where u was 100 and V was 160. The q u a n t i z e r r a n g e 2 was a p p r o x i m a t e l y 6a where o i s t h e v a r i a n c e o f " z t h e s i g n a l z. The c h o i c e o f a was a t r a d e o f f b e t w e e n d e c r e a s i n g q u a n t i z i n g n o i s e and i n c r e a s i n g s e n s i t i v i t y t o c h a n n e l n o i s e . I n a w e l l d e s i g n e d DPCM s y s t e m employ-i n g optimum p r e d i c t i o n and where t h e q u a n t i z e r r a n g e J2 38 i s s c a l e d a c c o r d i n g t o cr t h e n ~ ? =- (1 - a 2 ) x 2 - n + - 5 - { n _ ( l - a 2 ) x 2 } (5-2) q (1 - a ) Where n = q u a n t i z a t i o n n o i s e when t h e q u a n t i z e r i n p u t s i g n a l ^ z h a s u n i t v a r i a n c e . n = c h a n n e l n o i s e when t h e q u a n t i z e r i n p u t s i g n a l z c h a s u n i t v a r i a n c e . ~~2 x = i n p u t s i g n a l power. I t c a n be s e e n i f optimum p r e d i c t i o n i s u s e d t h e n t h e o r e t -i c a l l y t h e q u a n t i z i n g n o i s e i s d e c r e a s e d and t h e c h a n n e l n o i s e i s t h e same as f o r a PCM s y s t e m . T h e r e a r e two a s s u m p t i o n s u n d e r l y i n g t h i s f o r m u l a w h i c h a r e n o t s a t i s f i e d i n t h i s c a s e . F i r s t , i t i s assumed t h a t q u a n t i z i n g n o i s e i s n e g l i g i b l e i n t h e f e e d b a c k l o o p . T h i s i s n o t t r u e f o r t h e low number o f b i t s u s e d i n t h i s s y s t e m . S e c o n d l y i t i s assumed t h a t t h e q u a n t i z e r r a n g e and h e n c e t h e c h a n n e l n o i s e power a r e s c a l e d down e x a c t l y by t h e 2 f a c t o r (1 - a ) . I n p r a c t i c e w i t h t h i s s y s t e m i t was f o u n d t h a t R (1) i f a a p p r o a c h e d t h e v a l u e o f ^rhr[ • . • • , ^ R(0) t h e n t h e s e n s i t i v i t y o f t h e e r r o r power t o c h a n n e l , n o i s e i n c r e a s e d . The e f f e c t o f CL on t h e s y s t e m SNR i s shown i n f i g u r e -28. I t c a n be s e e n t h a t as a a p p r o a c h e s one t h e s y s t e m i s v e r y s t r o n g l y a f f e c t e d by n o i s e , w h i l e i f a i s a b o u t 0.9 t h e s y s t e m i s n o t as s e n s i t i v e t o t h e n o i s e a l t h o u g h t h e n o i s e f r e e p e r f o r m a n c e i s s t i l l n o t d r a s t -i c a l l y d e g r a d e d . F o r t h i s r e a s o n i t was d e c i d e d t o use an a o f 0.9 f o r a l l DPCM s i m u l a t i o n s . Once t h e s e d e s i g n c o n s i d e r a t i o n s h a d b e e n s e t t l e d , a s e t o f p i c t u r e s was g e n e r a t e d w i t h t h e number o f b i t s e q u a l t o 1,2,3. and 4, and w i t h P a s s u m i n g -2 -3 -4 v a l u e s o f 1/50, .10 , 1 0 and 10 . The r a n g e o f t h e p a r a m e t e r s f o r t h e DPCM s y s t e m were c h o s e n u s i n g t h e same c o n s i d e r a t i o n s as f o r t h e PCM s y s t e m . F i g u r e -29 shows a g r a p h o f t h e SNR a t t a i n e d by t h e v a r i o u s DPCM s y s t e m s . I t was f o u n d t h a t when P e q u a l l e d 10 t h e DPCM s y s t e m p r o d u c e d p i c t u r e s o f s u c h p o o r q u a l i t y t h a t t h e y c o u l d be i g n o r e d . A f t e r t h e s e s e t s o f PCM and DPCM n o i s y p i c t u r e s h a d b e e n g e n e r a t e d an a t t e m p t was made t o r e d u c e t h e v i s i b i l i t y o f n o i s e p r o d u c e d by c h a n n e l e r r o r s . B e c a u s e o f t h e v a s t l y d i f f e r e n t n a t u r e , o f t h e n o i s e i n t h e PCM and DPCM p i c t u r e s , i t was n e c e s s a r y t o d e v e l o p two f i l t e r i n g r o u t i n e s , one f o r PCM p i c t u r e s and one f o r DPCM p i c t u r e s . 5.2.2 P i c t u r e S m o o t h i n g P r o g r a m s The f i l t e r s u s e d , were i n b o t h c a s e s n o n -l i n e a r . L i n e a r f i l t e r i n g o p e r a t i o n s were t e s t e d b u t i t was f o u n d t h e b l u r r i n g i n t r o d u c e d by t h e low p a s s n a t u r e o f t h e s e f i l t e r s was more a n n o y i n g t h a n t h e n o i s e t h e y were s u p p o s e d t o remove. I n "a PCM s y s t e m , e a c h p o i n t i s t r a n s m i t t e d i n d e p e n d e n t l y . Thus i f a t r a n s m i s s i o n e r r o r o c c u r s , o n l y a s i n g l e p o i n t w i l l be c h a n g e d . As a r e s u l t , PCM p i c t u r e s w i t h e r r o r s t e n d t o h a v e n o i s e w h i c h c a n be d e s c r i b e d as " s a l t a nd p e p p e r " n o i s e . Some e x a m p l e s o f n o i s y PCM p i c t u r e s a r e shown i n a p p e n d i x -B. A method f o r r e d u c i n g s a l t a nd p e p p e r n o i s e was m e n t i o n e d 33 by R o s e n f e l d and o p e r a t e s as f o l l o w s . 72 (J-1) ( J + D ( I - D o o - Q O- x- 0 (1+1) o - o o F i g . 30 D a t a p o i n t s u s e d by t h e PCM f i l t e r t o smooth p o i n t X C o n s i d e r t h e p o i n t X i n f i g u r e -30'. To d e t e r m i n e i f X was r e c e i v e d c o r r e c t l y f o r m t h e d i f f e r e n c e b e t w e e n X and t h e a v e r a g e o f i t s e i g h t n e a r e s t n e i g h b o u r s . I f t h e d i f f e r e n c e i s l e s s t h a n a t h r e s h o l d v a l u e assume t h e p o i n t i s c o r r e c t and l e a v e i t . I f t h e d i f f e r e n c e e x c e e d s t h e t h r e s h o l d , r e p l a c e i t by t h e a v e r a g e v a l u e . I n o t h e r words i f t h e p o i n t X h a s a v a l u e o f I P ( i , j ) f o r m 3 3 D = E E l P ( i + k - 2 , j + 1-2) - 9 - I P ( i , j ) } | (5-3) B k = l 1=1 I f D < T h r e s h o l d 0 P ( i , j ) = I P ( i , j ) I f D > T h r e s h o l d O P ( i , j ) = AVG , 3 3 AVG = i{ E E IP(i+k-2,j+1-2) - I P ( i , j ) } 8 k = l 1=1 A s u b r o u t i n e c a l l e d F I L T E R was w r i t t e n i n F o r t r a n t o i m p l e m e n t t h i s a l g o r i t h m . The p r o g r a m was r u n w i t h t h e d a t a h a n d l i n g p r o g r a m s PROCR and FPACK and a s e t o f 73 p i c t u r e s was p r o d u c e d by f i l t e r i n g t h e PCM p i c t u r e s w h i c h h a d b e e n p r o d u c e d p r e v i o u s l y . DPCM p i c t u r e n o i s e due t o c h a n n e l e r r o r s h as q u i t e a d i f f e r e n t n a t u r e f r o m PCM n o i s e and r e q u i r e d a c o m p l e t e l y d i f f e r e n t f i l t e r i n g s t r a t e g y . T h i s n a t u r e c a n be v i e w e d i n two ways. The f i r s t way i s t o c o n s i d e r t h e DPCM s o u r c e d e c o d e r t o be a l o w p a s s f i l t e r . Thus any w i d e b a n d n o i s e a d d e d t o y\ by t h e c h a n n e l n o i s e w i l l be f i l t e r e d a n d a low f r e q u e n c y n o i s e w i l l a p p e a r a t t h e s y s t e m o u t p u t x^. I t c a n be shown ^ t h a t low f r e q u e n c y n o i s e i n t h e v i d e o s i g n a l g i v e s r i s e t o two d i m e n s i o n a l n o i s e w h i c h i s v e r y a n i s o t r o p i c . The two d i m e n s i o n a l n o i s e w i l l h a v e a w i d e b a n d o f f r e q u e n c i e s i n t h e v e r t i c a l d i r e c t i o n and o n l y low f r e q u e n c i e s p r e s e n t i n t h e h o r i z o n t a l d i r e c t i o n . As a r e s u l t t h e n o i s e w i l l v a r y m u c h more r a p i d l y i n t h e v e r t i c a l t h a n i n t h e h o r i z o n t a l d i r e c t i o n . The n o i s e a p p e a r s as a s e r i e s o f h o r i z o n t a l s t r e a k s whose l e n g t h s d e p e n d on t h e p a r a m e t e r ct w h i c h d e t e r m i n e s t h e f i l t e r b a n d w i d t h . A s e c o n d v i e w o f t h e n o i s e i s t o c o n s i d e r t h e s y s t e m o u t p u t ( f i g u r e -25) • \ /N. A 2 ^ , = Y_ + <**Y___ + a '^1-2 +•'• ' (5-4) . n x. = S . (5-5) 1 j=0 1 3 I t c a n be s e e n t h a t e a c h r e c e i v e d p o i n t depends n o t o n l y on t h e p r e s e n t v a l u e o f y\ b u t a l s o on a w e i g h t e d sum o f p a s t v a l u e s o f y\ . I f one o f t h e y ^ i s i n c o r r e c t , i t w i l l c a u s e an e r r o r i n Jt\ and a l s o i n s u b s e q u e n t p o i n t s "x\ +k i k = l , 2 ... u n t i l i t s e f f e c t h a s d e c a y e d . The d e c a y r a t e d e p e n d s d i r e c t l y on a . I f a i s c l o s e t o one, t h e e r r o r w i l l d e c a y s l o w l y and a l o n g e r r o r s t r e a k w i l l a p p e a r . I f a i s l e s s t h a n one, t h e s t r e a k l e n g t h d e c r e a s e s p r o p o r t i o n a t e l y . B e c a u s e o f t h e a n i s o t r o p i c n a t u r e o f t h e DPCM n o i s e , i t i s p o s s i b l e t o d i s t i n g u i s h t h e n o i s e f r o m t h e p i c t u r e m a t e r i a l . o n l y by i t s h i g h f r e q u e n c i e s i n t h e y d i r e c t i o n . A l i n e a r f i l t e r w h i c h f i l t e r e d t h e p i c t u r e o n l y i n t h e y d i r e c t i o n was t r i e d . T h i s f i l t e r i n t r o d u c e d more d e g r a d a t i o n due t o b l u r r i n g t h a n i t removed. The f i l t e r w h i c h was f i n a l l y u s e d o p e r a t e d as f o l l o w s . (I-D (I+D O PM -X p - o d l = P - PM (5-6) d2 = PP - p F i g . 31 D a t a p o i n t s u s e d by t h e DPCM f i l t e r t o smooth p o i n t X X i s a g a i n t h e p o i n t b e i n g c o n s i d e r e d . P i s t h e v a l u e o f t h e p i c t u r e f u n c t i o n a t p o i n t X i n t h e i n p u t p i c t u r e . OP w i l l be t h e v a l u e o f t h e p i c t u r e f u n c t i o n i n t h e o u t p u t p i c t u r e . F o r m t h e two d i f f e r e n c e s d l and d2 and t h e n p e r f o r m t h e l o g i c shown i n f i g u r e -32. Yes OP = j ( PM •+ -PP ) OP = I P ( i , j ) F i g . 32 F i l t e r a l g o r i t h m f o r t h e DPCM f i l t e r i n g r o u t i n e I t c a n be s e e n t h a t s u c h a f i l t e r w i l l smooth any p a r t s o f t h e p i c t u r e w h i c h change r a p i d l y i n t h e v e r t i c a l d i r e c t i o n . T h i s f i l t e r was n o t as s u c c e s s f u l as t h e PCM f i l t e r . The a l g o r i t h m b r e a k s down when P becomes l a r g e enough t h a t a d j a c e n t e r r o r l i n e s o c c u r . A d j a c e n t e r r o r l i n e s were f o u n d t o be a p r o b l e m when P was more t h a n 1 0 ~ 2 . A p r o g r a m NLDPMF u s i n g t h i s a l g o r i t h m was w r i t t e n u s i n g a c o m b i n a t i o n o f F o r t r a n and a s s e m b l y l a n g u a g e and was u s e d w i t h t h e d a t a p r o g r a m s PROCR and FPACK. W i t h t h e s e p r o g r a m s a s e t o f f i l t e r e d DPCM p i c t u r e s was 76 p r o d u c e d by f i l t e r i n g a l l t h e DPCM p i c t u r e s p r e v i o u s l y p r o d u c e d . > The o b j e c t i v e o f g e n e r a t i n g a l l t h e s e p i c t u r e s was t o s t u d y t h e s u b j e c t i v e e f f e c t o f t h e c h a n n e l n o i s e . I t was d e c i d e d t o u s e a p i c t u r e r a t i n g s y s t e m where s u b j e c t s w o u l d compare t h e n o i s y p i c t u r e s w i t h a s e t o f s t a n d a r d p i c t u r e s . The t h i r d d i s t i n c t p i c t u r e p r o c e s s i n g p r o g r a m was DGRADE w h i c h p r o d u c e d t h e s e s t a n d a r d s . 5.2.3 DGRADE a S t a n d a r d P r o d u c i n g P r o g r a m F o r a r a t i n g , s u b j e c t s were a s k e d t o compare t h e t e s t p i c t u r e s w i t h a s e t o f s t a n d a r d p i c t u r e s . When a s u b j e c t h a d d e c i d e d w h i c h s t a n d a r d h a d t h e same q u a l i t y as t h e t e s t p i c t u r e , t h e SNR o f t h e s t a n d a r d "X" was a s s i g n e d t o t h e t e s t p i c t u r e as an i n d i c a t i o n o f i t s q u a l i t y . The t e s t p i c t u r e i s t h e n s a i d t o have an e q u i v a l e n t SNR o f X db. The s e t o f s t a n d a r d p i c t u r e s h o u l d i d e a l l y s a t i s f y two c o n d i t i o n s . F i r s t , t h e q u a l i t y r a n g e i n t h e s t a n d a r d p i c t u r e s must be l a r g e enough t o match t h e r a n g e o f t e s t p i c t u r e q u a l i t y . S e c o n d , f o r c o n s i s t a n t r e s u l t s , t h e n a t u r e o f i m p a i r m e n t i n t h e s t a n d a r d p i c t u r e s s h o u l d be t h e same as t h a t i n t h e t e s t p i c t u r e s . The s e c o n d c o n d i t i o n was i m p o s s i b l e t o s a t i s f y s i n c e t h e PCM and DPCM p i c t u r e s h a d f o u r d i s t i n c t t y p e s o f i m p a i r m e n t . I n t h e PCM p i c t u r e s , d e g r a d a t i o n was due t o t h e low number o f b i t s u s e d and c h a n n e l n o i s e . DPCM p i c t u r e s were d e g r a d e d by t h e same f a c t o r s b u t t h e y p r o d u c e e r r o r s whose a p p e a r a n c e was d i f f e r e n t f r o m t h e PCM e r r o r s . The s e t o f s t a n d a r d s w h i c h were u s e d were 34 g e n e r a t e d u s i n g a method s u g g e s t e d by S c h r o e d e r . The o u t p u t s i g n a l i s g i v e n by x\ = (1 + a 2 ) " 1 / 2 x i ( l + a - E i ) (5-7) Where i s a n o i s e s i g n a l d e f i n e d by t h e f o l l o w i n g e q u a t i o n s . e. = +1 e. = 0 (5-8) l — l e.'E. = 6 . . e . • x. = 0 1 J 2-J i i T h i s p r o d u c e s p i c t u r e s whose SNR was g i v e n by SNR = 1 / a 2 (5-9) A p r o g r a m c a l l e d DGRADE was w r i t t e n f o r u s e w i t h PROCES w h i c h p r o d u c e d an o u t p u t as d e f i n e d by e q u a t i o n ( 5 - 7 ) . The n o i s e p r o c e s s was s i m u l a t e d u s i n g t h e random number p r o g r a m FRAND. U s i n g t h i s p r o g r a m and a p p r o p r i a t e <* a s e t o f p i c t u r e s was p r o d u c e d w i t h SNR's o f 6, 10, 14, 18, 22 and 26 db, f o r u s e i n t h e s u b j e c t i v e t e s t s as s t a n d a r d s . T h i s r a n g e o f SNR was c h o s e n a f t e r some i n s p e c t i o n o f t h e p r o g r a m s o u t p u t . I n a d d i t i o n t o g e n e r a t i n g t h e s e s t a n d a r d s , p i c t u r e s w i t h SNR o f 8, 12 a n d 16 db were g e n e r a t e d . T h e s e p i c t u r e s were i n c l u d e d 78 as t e s t p i c t u r e s i n t h e s u b j e c t i v e t e s t s t o c h e c k t h e r e s u l t s . 5.2.4 S i m u l a t i o n P r o g r a m Summary T h i s s e c t i o n h as d e s c r i b e d p i c t u r e p r o c e s s i n g r o u t i n e s w h i c h p r o d u c e d t h r e e s e t s o f p i c t u r e s . F i r s t a s e t o f p i c t u r e s w h i c h s i m u l a t e d p i c t u r e s w h i c h h a d b e e n t r a n s m i t t e d by PCM and DPCM s y s t e m s w i t h n o i s y c h a n n e l s were d e s c r i b e d . S e c o n d a s e t o f p i c t u r e s was p r o d u c e d by f i l t e r i n g t h e n o i s y PCM a n d DPCM p i c t u r e s . T h i r d , a s e t o f s t a n d a r d p i c t u r e s was g e n e r a t e d f o r u s e i n a s u b j e c t i v e t e s t . The n e x t s e c t i o n w i l l d i s c u s s t h e s u b j e c t i v e t e s t s w h i c h were p e r f o r m e d w i t h t h e p i c t u r e s . 5.3 S u b j e c t i v e T e s t P r o c e d u r e s As m e n t i o n e d i n t h e p r e v i o u s s e c t i o n i t was d e c i d e d t o u s e a r a t i n g t y p e o f s u b j e c t i v e t e s t f o r d e t e r m i n i n g t h e s u b j e c t i v e q u a l i t y o f t h e t e s t p i c t u r e s . The p r o g r a m s i n t h e p r e v i o u s s e c t i o n h a d p r o d u c e d 59 23g i n c h s q u a r e t e s t p i c t u r e s . The s e t o f p i c t u r e s c o n t a i n e d t w e l v e PCM p i c t u r e s , s i x t e e n DPCM p i c t u r e s , t w e l v e f i l t e r e d PCM p i c t u r e s , s i x t e e n f i l t e r e d DPCM p i c t u r e s and t h r e e t e s t s t a n d a r d p i c t u r e s . B e f o r e a t e s t , t h e s u b j e c t was g i v e n a c o p y o f t h e i n s t r u c t i o n w h i c h a r e r e p r o d u c e d b e l o w . You w i l l be a s k e d t o r a t e t h e s u b j e c t i v e q u a l i t y o f a s e t o f p i c t u r e s by c o m p a r i n g t h e t e s t p i c t u r e s w i t h a s e t o f s t a n d a r d p i c t u r e s . The s t a n d a r d p i c t u r e s a r e i d e n t i f i e d by numbers w h i c h a p p e a r on t h e r i g h t s i d e s o f t h e p i c t u r e s . 79 You w i l l be g i v e n one t e s t p i c t u r e a t a t i m e . F o r e a c h t e s t p i c t u r e , w r i t e on t h e t e s t f o r m t h e number o f t h e s t a n d a r d p i c t u r e w h i c h y o u f e e l has the. same q u a l i t y as t h e t e s t p i c t u r e . I f t h e t e s t p i c t u r e q u a l i t y i s b e t w e e n two s t a n d a r d s , a s s i g n t h e t e s t p i c t u r e a r a t i n g w h i c h i s midway b e t w e e n t h e two s t a n d a r d v a l u e s . I f t h e q u a l i t y o f t h e t e s t p i c t u r e i s w o r se t h a n t h e q u a l i t y o f t h e p o o r e s t s t a n d a r d , g i v e i t a r a t i n g o f 0 ( z e r o ) . I f t h e q u a l i t y o f t h e t e s t p i c t u r e i s b e t t e r t h a n t h a t o f t h e b e s t s t a n d a r d g i v e i t a r a t i n g o f 2 8. V i e w t h e p i c t u r e s f r o m a d i s t a n c e o f 15 i n c h e s . P l e a s e do n o t t o u c h t h e f r o n t o f t h e p h o t o g r a p h s . F o r t h e t e s t , t h e p i c t u r e s were a r r a n g e d i n random o r d e r . Two d i f f e r e n t random o r d e r i n g s were u s e d i n o r d e r t o r e d u c e t h e e f f e c t o f any i n t e r a c t i o n b e t w e e n t h e t e s t p i c t u r e s . E a c h o f t h e t e n s u b j e c t s was t e s t e d i n d i v i d u a l l y . The s u b j e c t s were a l l g r a d u a t e s t u d e n t s i n t h e D e p a r t m e n t o f E l e c t r i c a l E n g i n e e r i n g a t t h e U n i v e r s i t y o f B r i t i s h C o l u m b i a and h a d no p r e v i o u s e x p e r i e n c e w i t h s u b j e c t i v e e v a l u a t i o n o f p i c t u r e s . 5 . 4 ... S u b j e c t i v e T e s t D a t a Once t h e t e s t h a d b e e n c o m p l e t e d , t h e d a t a f r o m t h e s u b j e c t s ' answer s h e e t s was u n s c r a m b l e d and c o m b i n e d t o o b t a i n t e n e s t i m a t e s o f p i c t u r e q u a l i t y f o r e a c h p i c t u r e . F o r a p a r t i c u l a r p i c t u r e , t h e t e n e s t i m a t e s by t h e d i f f e r e n t s u b j e c t s a r e i n g e n e r a l n o t i d e n t i c a l . I t was d e s i r a b l e t o assume t h a t f o r a p a r t i c u l a r p i c t u r e t h e g r a d e s a r e s a m p l e s drawn f r o m a p o p u l a t i o n w i t h a n o r m a l d i s t r i b u t i o n w i t h p a r a m e t e r s u and o . . I f t h i s a s s u m p t i o n i s t r u e , i t w o u l d be p o s s i b l e t o u s e t h e e x t e n s i v e t h e o r y w h i c h i s a v a i l a b l e 80 c o n c e r n i n g s a m p l i n g f r o m n o r m a l p o p u l a t i o n s . To c h e c k 39 t h i s a s s u m p t i o n , a K o l m o g o r o v - S m i r n o v t e s t was p e r -f o r m e d on a l l s e t s o f d a t a . The h y p o t h e s i s was a c c e p t e d a t t h e 5% s i g n i f i c a n c e l e v e l f o r a l l b u t one s e t o f d a t a a n d was a c c e p t e d by a l l s e t s o f d a t a a t t h e 1% s i g n i f i c a n c e l e v e l . E a c h p i c t u r e was a s s i g n e d a q u a l i t y w h i c h was t h e a v e r a g e o f t h e s a mple d a t a f o r t h a t p i c t u r e . The 95% c o n f i d e n c e i n t e r v a l was c a l c u l a t e d ( e q u a t i o n 5-10) u s i n g t h e s t u d e n t t d i s t r i b u t i o n . s s — X — X x - t < y < x + t fc;-irn /n-1 /n-1 The d a t a a p p e a r e d t o be. q u i t e c o n s i s t a n t w i t h i n e a c h s e t and between s e t s . The c o n s i s t a n c y w i t h i n e a c h s e t o f d a t a i s i n d i c a t e d by t h e r e a s o n a b l y s m a l l c o n f i d e n c e i n t e r v a l s . The c o n s i s t a n c y b e t w e e n s e t s o f d a t a c a n be o b s e r v e d i n f i g u r e s 33, 34, 35 and 36, where t h e s u b j e c t i v e s i g n a l t o n o i s e r a t i o s a r e p l o t t e d f o r t h e f o u r s y s t e m s . Two p o i n t s i n i t i a l l y a p p e a r e d t o be i n e r r o r . I t a p p e a r e d t h a t t h e d a t a f o r t h e s e p o i n t s h a d b e e n r e v e r s e d . However, a c a r e f u l c h e c k r e v e a l e d no b o o k k e e p i n g e r r o r s . As a r e s u l t a s h o r t t e s t was made w i t h t h e two anamolous p o i n t s and a few a d j a c e n t p o i n t s . The r e s u l t s f r o m t h i s s p o t c h e c k were i n a g r e e m e n t w i t h t h e r e s t o f t h e d a t a . Once t h e d a t a h a d b e e n t e s t e d t o v e r i f y t h e n o r m a l i t y a s s u m p t i o n and c o n f i d e n c e i n t e r v a l s c a l c u l a t e d , s e v e r a l g r a p h s were p l o t t e d i n o r d e r t o p l a c e any g e n e r a l c o n c l u s i o n s i n e v i d e n c e . 0 I I L_ I I lo-1 io"2 ier3 io-4 BIT ERROR PROBABILITY F i g u r e - 33 S u b j e c t i v e SNR v e r s u s P f o r a PCM s y s t e m . 10 -I 10 r 2 10 r 3 10" r*4 BIT ERROR PROBABILITY F i g u r e - 34 S u b j e c t i v e SNR v e r s u s P f o r a DPCM s y s t e m . F i g u r e - 36 S u b j e c t i v e SNR v e r s u s P f o r a f i l t e r e d DPCM s y s t e m . 0 I 1 — — ' 1 1 I0'1 IO~2 IO"3 I0"4 BIT ERROR PROBABILITY oo F i g u r e - 35 S u b j e c t i v e SNR v e r s u s P f o r a ^ f i l t e r e d PCM s y s t e m . i 6 4 g i d 3 CD O CC CL g i o 2 cc cc U J Si id1 OBJECTIVE SNR SUBJECTIVE SNR i o 4 >-g id3 1 CD O cc 8 ioi or UJ m lO1 I 2 3 4 NUMBER OF BITS PER SAMPLE F i g u r e - 37 S u b j e c t i v e i s o - q u a l i t y l i n e s and l i n e s o f c o n s t a n t mean-s q u a r e e r r o r f o r a PCM s y s t e m . 10 OBJECTIVE SNR SUBJECTIVE SNR _L F i g u r e 1 2 3 4 NUMBER OF BITS PER SAMPLE - 38 S u b j e c t i v e i s o - q u a l i t y l i n e s and l i n e s o f c o n s t a n t m e a n - s q u a r e e r r o r f o r a DPCM s y s t e m . 00 84 Two t y p e s o f s i g n a l t o n o i s e r a t i o (SNR) a r e r e f e r r e d t o on t h e g r a p h s . The f i r s t , t h e o b j e c t i v e SNR i s d e f i n e d by e q u a t i o n ( 5 - 1 1 ) . ? SNR . . = 1 (5-11) (x. - x.) The s e c o n d , t h e s u b j e c t i v e SNR i s t h e v a l u e w h i c h was o b t a i n e d f r o m t h e s u b j e c t i v e t e s t s . Two s e t s o f g r a p h s were p l o t t e d . The f i r s t c o m p r i s e s g r a p h s s h o w i n g s u b j e c t i v e SNR p l o t t e d v e r s u s b i t e r r o r p r o b a b i l i t y P w i t h t h e number o f b i t s p e r sample N as a p a r a m e t e r . I n t h e s e c o n d s e t o f g r a p h s , t h e p a r a m e t e r was t h e q u a l i t y q and l i n e s o f c o n s t a n t q u a l i t y o r i s o - q u a l i t y c u r v e s were p l o t t e d on t h e (P-N) p l a n e . From t h e s e c u r v e s i t i s p o s s i b l e t o draw some c o n c l u s i o n s . 5.5 D a t a P r e s e n t a t i o n and R e s u l t s The i s o - q u a l i t y g r a p h s i n f i g u r e s 37 and 38 i l l u s t r a t e t h e p e r f o r m a n c e o f t h e PCM and DPCM s y s t e m s w i t h o u t f i l t e r i n g . C u r v e s o f c o n s t a n t m e a n - s q u a r e e r r o r (MSE) were p l o t t e d on t h e same a x i s i n o r d e r t o examine t h e r e l a t i o n s h i p b e t w e e n t h e s u b j e c t i v e q u a l i t y and t h e MSE. u c , p 2 , ^ , 2 (5-12) MSE = e = (x^ - x^) I t c a n be s e e n t h a t f o r t h e PCM s y s t e m t h e s h a p e o f t h e 85 MSE c u r v e s and t h e i s o - q u a l i t y c u r v e s a r e v e r y s i m i l a r . T h u s , f o r t h e r a n g e o f p a r a m e t e r s u s e d , t h e MSE w o u l d a p p e a r t o be a good i n d i c a t o r o f t h e s u b j e c t i v e p i c t u r e q u a l i t y . I n f i g u r e -38 s i m i l a r c u r v e s a r e shown f o r a DPCM s y s t e m . I t c a n be s e e n t h a t t h e s u b j e c t i v e q u a l i t y c u r v e s a r e a f f e c t e d more by c h a n n e l e r r o r t h a n t h e MSE c u r v e s . T h i s i s i n d i c a t e d by t h e f a c t t h a t t h e s u b j e c t i v e i s o -q u a l i t y l i n e s c u r v e t o t h e r i g h t more q u i c k l y t h a n t h e MSE l i n e s do. Thus i n t h e s t u d y o f c h a n n e l e r r o r s i n DPCM s y s t e m s , t h e MSE m i g h t be an o v e r o p t i m i s t i c i n d i c a t o r o f s u b j e c t i v e q u a l i t y . F i g u r e -39 was p l o t t e d s o t h a t t h e DPCM and PCM s y s t e m s c o u l d be compared. From t h e f i g u r e , i t c a n -3 be s e e n t h a t f o r good c h a n n e l s w i t h P l e s s t h a n 10 t h e DPCM s y s t e m s o u t p e r f o r m s t h e PCM s y s t e m . However, -2 -3 f o r c h a n n e l s e r r o r p r o b a b i l i t i e s b e t w e e n 10 and 10 , t h e c u r v e s c r o s s o v e r and t h e PCM s y s t e m p r o d u c e s p i c t u r e s w h i c h a r e s u b j e c t i v e l y b e t t e r . The c r o s s o v e r shows t h a t '' t h e MSE i s n o t a good i n d i c a t o r f o r c o m p a r i n g two d i f f e r e n t s o u r c e e n c o d i n g schemes s i n c e i f f i g u r e s 27 and 29 a r e compared i t c a n be s e e n t h a t t h e MSE o f t h e DPCM s y s t e m i s e q u a l t o o r b e t t e r t h a n t h e MSE o f t h e PCM s y s t e m f o r a l l v a l u e s o f P w h i c h a r e c o n s i d e r e d . T h i s i s i n a g r e e m e n t w i t h work done p r e v i o u s l y on s u b j e c t i v e n o i s e 17 19 w e i g h t i n g f u n c t i o n s ' , where i t was f o u n d t h a t t h e n o i s e w e i g h t i n g f u n c t i o n was l o w - p a s s i n n a t u r e . I n o t h e r 86 10' _ m |Q3 < CQ O a: o. glCj2 a: cr LU _ m io"1 PCM DPCM ± I 2 3 4 NUMBER OF BITS PER SAMPLE F i g u r e - 39 S u b j e c t i v e i s o - q u a l i t y l i n e s f o r t h e DPCM and PCM s y s t e m s . * 87 w o rds, low f r e q u e n c y was more a n n o y i n g t h a n h i g h f r e q u e n c y n o i s e . As m e n t i o n e d p r e v i o u s l y , t h e DPCM s o u r c e d e c o d e r b e h a v e s l i k e a low p a s s f i l t e r a n d c h a n g e s t h e w i d e b a n d c h a n n e l n o i s e i n t o a low f r e q u e n c y s i g n a l . No s u c h f i l t e r i n g a c t i o n t a k e s p l a c e i n a PCM s y s t e m . Thus i t w o u l d be e x p e c t e d t h a t t h e low f r e q u e n c y DPCM n o i s e c o u l d be more a n n o y i n g t h a n t h e w i d e b a n d PCM n o i s e e v e n t h o u g h t h e PCM n o i s e m i g h t be o f g r e a t e r power. I n o r d e r t o d e t e r m i n e t h e e f f e c t o f t h e n o i s e f i l t e r i n g , i s o - q u a l i t y c u r v e s f o r an o r d i n a r y PCM s y s t e m a n d one w i t h t w o - d i m e n s i o n a l s m o o t h i n g were p l o t t e d i n f i g u r e -40. I t c a n be s e e n f r o m t h i s c u r v e t h a t t h e f i l t e r d o e s a l l o w t h e s y s t e m t o o p e r a t e w i t h h i g h e r c h a n n e l e r r o r p r o b a b i l i t i e s . T h i s i m p r o v e m e n t c a n a l s o be s e e n i f f i g u r e s 33 and 35 a r e compared. S i m i l a r c u r v e s were p l o t t e d s o t h a t t h e DPCM f i l t e r a l g o g r i t h m c o u l d be a s s e s s e d ( f i g u r e - 4 1 ) . From t h e s e c u r v e s , i t c a n be s e e n t h a t f o r good c h a n n e l s , t h e f i l t e r l o w e r s t h e s u b j e c t i v e q u a l i t y w h i l e f o r p o o r c h a n n e l s t h e q u a l i t y i s t h e same as t h e u n f i l t e r e d s y s t e m . Thus i t a p p e a r s t h a t f i l t e r i n g DPCM p i c t u r e s w i t h t h e p r o p o s e d f i l t e r p r o d u c e d no imp r o v e m e n t i n q u a l i t y . The f a i l u r e o f t h i s f i l t e r was a t t r i b u t e d t o t h e f a c t t h a t i t p r o d u c e d some b l u r r i n g i n t h e p i c t u r e . T h u s , a l t h o u g h i t d i d r e d u c e t h e v i s i b i l i t y o f t h e n o i s e , t h e im p r o v e m e n t was more t h a n o f f s e t by t h e d e g r a d a t i o n due t o b l u r r i n g . I I I I I 1 1 1 L I 2 3 4 I 2 3 4 NUMBER OF BITS PER SAMPLE NUMBER OF BITS PER SAMPLE F i g u r e - 40 S u b j e c t i v e i s o - q u a l i t y l i n e s F i g u r e f o r t h e f i l t e r e d and u n f i l t e r e d PCM s y s t e m s . 41 S u b j e c t i v e i s o - q u a l i t y l i n e s f o r t h e f i l t e r e d a nd u n f i l t e r e d DPCM s y s t e m s . co 89 5.6 S u b j e c t i v e T e s t Summary I n t h i s c h a p t e r s u b j e c t i v e r a t i n g t e s t s were d e s c r i b e d w h i c h gave f a i r l y c o n s i s t a n t r e s u l t s . The t e s t s i n d i c a t e t h a t t h e s u b j e c t i v e q u a l i t y o f p i c t u r e s t r a n s m i t t e d by PCM s y s t e m s o v e r p o o r c h a n n e l s c a n be b e t t e r t h a n t h e s u b j e c t i v e q u a l i t y p r o d u c e d by DPCM s y s t e m s , e v e n t h o u g h t h e MSE o f t h e DPCM s y s t e m was s m a l l e r . The t e s t a l s o i n d i c a t e t h a t t h e PCM n o i s e f i l t e r t e s t e d i m p r o v e s t h e s u b j e c t i v e q u a l i t y o f t h e n o i s y p i c t u r e s w h i l e t h e p r o p o s e d DPCM f i l t e r p r o d u c e s no i m p r o v e m e n t and e v e n t e n d s t o l o w e r t h e q u a l i t y o f p i c t u r e s t r a n s m i t t e d o v e r good c h a n n e l s . 90 Neumonic S31 APPENDIX A. DISPLAY COMMANDS AND CONNECTIONS COMMANDS E f f e c t S32 LDX LDY Code 703107 703207 706302 705302 L o a d SOI 31 w i t h t h e c o n t e n t s o f t h e a c c u m u l a t o r L o a d SOI 32 w i t h t h e c o n t e n t s o f t h e a c c u m u l a t o r L o a d t h e x D/A c o n v e r t e r b u f f e r f r o m SOI 31 L o a d t h e y D/A c o n v e r t e r b u f f e r f r o m SOI 31 EXPS 705701 E x p o s e a p o i n t S F I N 705601 S k i p i f t h e d i s p l a y f l a g i s c l e a r CONNECTIONS S i g n a l Name From To SOI 31 E(13-22) P o s i t i o n D/A i n p u t s IOT 6302 L-3 * L o a d x D/A p u l s e IOT 5302 G-3 * L o a d y D/A p u l s e SOI 32 H ( l l - 2 2 ) G ( l l - 2 2 ) SBUSY SBUSY* F-10 CBUSY CBUSY* F-9 IOT 5601 G-8 F-8 IOT 5701 J-2 * E x p o s e p u l s e R e f e r e n c e O u t p u t VREF* V o l t a g e D/A #2 * i n d i c a t e s a p o i n t on t h e e x t e r n a l d i s p l a y e l e c t r o n i c s APPENDIX B. PCM AND DPCM TEST PICTURES T h i s a p p e n d i x c o n t a i n s c o p i e s o f t h e p i c t u r e s u s e d i n t h e s u b j e c t i v e t e s t s . E a c h p i c t u r e i s i d e n t i f i e d by a n i n e c h a r a c t e r c o d e w h i c h h a s t h e f o l l o w i n g f o r m XXXXnBTPm The f i r s t f o u r c h a r a c t e r s XXXX a r e a code i d e n t i f y i n g t h e t y p e o f s y s t e m s i m u l a t e d . The f o l l o w i n g c o d e s were u s e d PCMN PCM s y s t e m DPCM DPCM s y s t e m PNFL PCM s y s t e m w i t h f i l t e r i n g DPNL DPCM s y s t e m w i t h f i l t e r i n g DGRAD S u b j e c t i v e t e s t s t a n d a r d p i c t u r e The c h a r a c t e r n s p e c i f i e s t h e number o f b i t s p e r p i c t u r e e l e m e n t . The c h a r a c t e r m s p e c i f i e s t h e b i t e r r o r p r o b a b i l i t y , m E r r o r P r o b a b i l i t y 1 l o " 1 2 1 0 " 2 3 1 0 " 3 4 1 0 ~ 4 8 2 x l 0 - 2 F o r e x a m p l e DPNL3BTP4 r e p r e s e n t s a t h r e e b i t DPCM s y s t e m -4 w i t h f i l t e r i n g a nd a b i t e r r o r p r o b a b i l i t y o f 10 . P i c t u r e s p r o d u c e d by. t h e p r o g r a m DGRADE a r e i d e n t i f i e d by a d i f f e r e n t c o d e o f t h e f o r m DGRADssDB w h i c h r e p r e s e n t s a s t a n d a r d p i c t u r e w i t h a SNR o f s s d e c i b e l s . PCMN2BTP4 PCMN3BTP4 PCMN4BTP4 PCMN2BTP3 PCMN3BTP3 PCMN4BTP3 PCMN2BTP2 PCMN3BTP2 PCMN4BTP2 P0MN2BTPI PCMN3BTPI PCMN4BTPI 93 DPCMIBTP4 DPCM2BTP4 DPCM3BTP4 DPCMIBTP2 DPCM2BTP2 DPCM3BTP2 • H m Ll] DPCMIBTP8 DPCM2BTP8 DPCM3BTP8 96 DPNL3BTP4 DPNL4BTP4 DGRAD26DB DPNL3BTP8 D P N L 4 B T P 8 DGRAD06DB 97 REFERENCES 1. W.F. S c h r e i b e r , " P i c t u r e C o d i n g " . P r o c . I E E E , . v o l . 55, pp. 320-330, M a r c h 1967. 2. D.E. P e a r s o n , "A R e a l i s t i c M o d e l f o r V i s u a l Com-m u n i c a t i o n s y s t e m s " , P r o c . I E E E , v o l . 55, pp. 380-389, M a r c h 1967. 3. J.O. Limb, " S o u r c e - R e c e i v e r E n c o d i n g o f T e l e v i s i o n s i g n a l s " , P r o c . I E E E , v o l . 55, pp. 364-379, M a r c h 1967.. 4. W.K. P r a t t , J . Kane and H.C. Andrews, "Hadamard T r a n s f o r m Image C o d i n g " , P r o c . I E E E , v o l . 57, p . p . 58-68, J a n u a r y 1969. 5. A. H a b i b i and P.A. W i n t z , "Image C o d i n g by L i n e a r T r a n s f o r m a t i o n s and B l o c k Q u a n t i z a t i o n " , I E E E  T r a n s , on C o m m u n i c a t i o n T e c h n o l o g y , V o l . Com - 19 pp. 50-62, F e b r u a r y 19 71. 6. G.B. A n d e r s o n and T.S. Huang, " P i e c e w i s e F o u r i e r T r a n s f o r m a t i o n f o r P i c t u r e B a n d w i d t h C o m p r e s s i o n , I E E E T r a n s , on C o m m u n i c a t i o n T e c h n o l o g y , v o l . Com - 19, pp. 133-140, A p r i l 1971 7. P. M e r t z and F. G r a y , "A T h e o r y o f S c a n n i n g and i t s R e l a t i o n t o t h e C h a r a c t e r i s t i c s o f t h e T r a n s m i t t e d S i g n a l i n T e l e p h o t o g r a p h y and T e l e v i s i o n " , B e l l  S y s t . T e c h . J . y V o l . 13, pp. 464-515, J u l y 1934. 8. P. M e r t z , " T e l e v i s i o n - The S c a n n i n g P r o c e s s " , P r o c . o f t h e IRE, v o l . 29, pp. 529-537, O c t o b e r 1941. 9. E.R. K r e t z m e r , " S t a t i s t i c s o f T e l e v i s i o n S i g n a l s " , B e l l S y s t . T e c h . J . , v o l . 31, pp. 751-763, J u l y 1952. 10. J.B. O ' N e a l , " P r e d i c t i v e Q u a n t i z i n g S y s t e m s ( D i f -f e r e n t i a l P u l s e Code M o d u l a t i o n ) f o r t h e T r a n s m i s s i o n o f T e l e v i s i o n S i g n a l s " , B e l l S y s t . T e c h . J . , v o l . 45, pp. 689-721, May-June 1966. 11. S.D. B r a d l e y , " O p t i m i z i n g a Scheme f o r Run L e n g t h E n c o d i n g " , P r o c . I E E E C o r r e s p o n d e n c e ) , v o l . 57, pp. 108-109, J a n u a r y 1969. 12. W.S. M i c h e l , "A C o d e d F a c s i m i l e S y s t e m " , 1957 IRE  Wescon. Conv. R e c . , p t . 2, pp. 84093. 13. L . E . F r a n k s , "A m o d e l f o r t h e Random V i d e o P r o c e s s " , B e l l S y s . T e c h . J . y o l . 45, pp. 609-629, A p r i l 1966. 14. N.3. J a y a n t , " A d a p t i v e D e l t a M o d u l a t i o n w i t h a O n e - B i t Memory", B e l l S y s . T e c h . J . , v o l . 49, pp. 321-343, M a r c h 1970. 15. J.O. Limb and F.W. Mounts, " D i g i t a l D i f f e r e n t i a l Q u a n t i z e r f o r T e l e v i s i o n " , B e l l Sy.s. T e c h . - J . , v o l . 48, pp. 2583-2599, September 1969. 16. L.C. W i l k i n s and P.A. W i n t z " , B i b l i o g r a p h y on D a t a C o m p r e s s i o n , P i c t u r e P r o p e r t i e s and P i c t u r e C o d i n g " , I E E E T r a n s r o r i - r t n f o r m a t i b n ' - ' T h e o r y, v o l . I T - 1 7 , pp. 180-197, M a r c h 1971. 17. J.D. D a r s t o w and H.N. C h r i s t o p h e r , "The M e a s u r e m e n t o f Random Monochrome V i d e o I n t e r f e r e n c e " , T r a n s . A I E E , v o l . 72, pp. 735-741, J a n u a r y 1954. 99 18. R.C. B r a i n a r d , F.W. Dammerer, and E.G. Kimme, " E s t i m a t i o n o f t h e S u b j e c t i v e E f f e c t s o f N o i s e i n L o w - R e s o l u t i o n T e l e v i s i o n S y s t e m s " , IRE T r a n s . on I n f o r m a t i o n T h e o r y , v o l . I t - 8 , pp. 99-106, F e b r u a r y 1962. 19. R.C. B r a i n a r d , " L o w - R e s o l u t i o n TV:. S u b j e c t i v e E f f e c t s o f N o i s e A d d e d to. a S i g n a l " , B e l l S y s . T e c h . J . , v o l . 46, pp. 233-259, J a n u a r y 1967. 20. T.S Huang, " T w o - D i m e n s i o n a l Power S p e c t r u m o f T e l e v i s i o n Random N o i s e " , Q u a r t e r l y P r o g r e s s  R e p t . 69, M.I.T. R e s e a r c h L a b . o f E l e c t r o n i c s , C a m b r i d g e , Mass., pp. 143-149, A p r i l 1963. 21. T.S. Huang, "The S u b j e c t i v e E f f e c t o f T w o - D i m e n s i o n a l P i c t o r i a l N o i s e " , I E E E T r a n s , on I n f o r m a t i o n T h e o r y , v o l . I T - 1 1 , p p . 43-53, J a n u a r y 1965. 22. T.S. Huang and M.T. C h i k h a o u i , "The E f f e c t o f BSC on PCM P i c t u r e Q u a l i t y " , I E E E T r a n s , on I n f o r m a t i o n  T h e o r y , v o l . I T - 1 3 , p p . 270-274, A p r i l 1967. 23. R.A. B r u c e , "Optimum P r e - E m p h a s i s and De-Emphasis N e t w o r k s f o r T r a n s m i s s i o n o f T e l e v i s i o n by PCM", I E E E T r a n s , on C o m m u n i c a t i o n T e c h n o l o g y , v o l . COM-12, pp. 91-96, September 1964. 24. F.W. M o u n t s , "Low R e s o l u t i o n TV: An E x p e r i m e n t a l D i g i t a l S y s t e m f o r E v a l u a t i o n B a n d w i d t h - R e d u c t i o n T e c h n i q u e s " , B e l l S y s . T e c h . J . , v o l . 46, pp. 167-19 8, J a n u a r y 1967. 100 25. R.B. M u r r a y and J . J . M a n n i n g , "Response o f E n d -Window P h o t o m u l t i p l i e r T u b e s as a F u n c t i o n o f i T e m p e r a t u r e " , IRE T r a n s , on N u c l e a r S c i e n c e , v o l . NS-7,.pp. 80-86, J u n e - S e p t . 1960. 26. W.E. S p i c e r and F. Wooten, " P h o t o e m i s s i o n and P h o t o m u l t i p l i e r s " , P r o c . I E E E , v o l . 51, pp. 1119-1126, A u g u s t 1963. 27. R e f e r e n c e D a t a f o r R a d i o E n g i n e e r s , New Y o r k : I n t e r n a t i o n a l T e l e p h o n e and T e l e g r a p h C o r p o r a t i o n , 1967, pp. 408-411. 28. J.G. C o s s a l t e r , "A Computer V i s u a l - I n p u t S y s t e m f o r t h e A u t o m a t i c R e c o g n i t i o n o f B l o o d C e l l s " , M.A.Sc. T h e s i s , D e p a r t m e n t o f E l e c t r i c a l E n g i n e e r i n g U n i v e r s i t y o f B r i t i s h C o l u m b i a , V a n c o u v e r 8, B.C. Canada. 29. H.V. S o u l e , E l e c t r o - O p t i c a l P h o t o g r a p h y a t Low  I l l u m i n a t i o n L e v e l s , New Y o r k , W i l e y , 196 8, C h a p t e r 7 3,0. p . P a l f f y - M u h o r a y . , " E f f e c t o f C h a n n e l T r a n s m i s s i o n E r r o r s on DPCM S y s t e m s " , M.A.Sc. T h e s i s , D e p a r t m e n t Of E l e c t r i c a l E n g i n e e r i n g , U n i v e r s i t y o f B r i t i s h C o l u m b i a , V a n c o u v e r 8, B.C., Canada, M a r c h 1969. 31. J . Yan, "A S u b j e c t i v e E v a l u a t i o n o f t h e E f f e c t s o f D i g i t a l C h a n n e l E r r o r s i n PCM and DPCM V o i c e Com-• -mun i c a t i o n - ' Sy s terns "., M; A. S c. - The s i s; - Dep a r tmen t o f E l e c t r i c a l E n g i n e e r i n g , U n i v e r s i t y o f B r i t i s h C o l u m b i a , V a n c o u v e r , 8, B.C.,. Canada, May 1971. 101 32. R.W. D o n a l d s o n , " O p t i m i z a t i o n o f PCM S y s t e m s Which Use N a t u r a l B i n a r y C o d e s " , P r o c . I E E E ( C o r r e s -p o n d e n c e ) v o l . 56, pp. 1252-1253, J u l y 1966. 33. A R o s e n f e l d , P i c t u r e P r o c e s s i n g by Computer, New Y o r k : A c a d e m i c P r e s s , 1969. 34. M.R. S c h r o e d e r , " R e f e r e n c e S i g n a l f o r S i g n a l Q u a l i t y S t u d i e s " , J . A c o u s t . Soc. Am., v o l . 44, pp. 1735-1736, J u n e 1968. 35. D.S. S e r a p h i n , "A F a s t Random Number G e n e r a t o r f o r IBM 360, "Commun. A s s o c . Comput. Mach., v a l . 12, pp. 695, December 1969. 36. T.H. N a y l o r , J . L . L a l i n t f y , D.S. B u r d i c k , and K. Chu, Computer S i m u l a t i o n T e c h n i q u e s , New Y o r k : W i l e y , 19 66, C h a p t e r 3. 37. B.M. R o s e n h e c k , "FASTFAX, a S e c o n d G e n e r a t i o n . F a c s i m i l e S y s t e m E m p l o y i n g Redundancy R e d u c t i o n T e c h n i q u e s " , I E E E T r a n s on C o m m u n i c a t i o n  T e c h n i q u e s , v o l . COM-18, pp. 772-778, December 1970. 38. K.Y. Chang and R.W. D o n a l d s o n , " A n a l y s i s and O p t i m i z a t i o n o f D i f f e r e n t i a l PCM S y s t e m s O p e r a t i n g o v e r N o i s y C h a n n e l s " , t o be s u b m i t t e d f o r p u b l i c a t i o n t o t h e I E E E T r a n s , on C o m m u n i c a t i o n s T e c h n o l o g y . 39. B.W. L i n d g r e n , S t a t i s t i c a l T h e o r y , New Y o r k : •: M a c M i l l a n Company^ 1 1962, pp. 300. 40. G.P. M a r s t o n , "The D e s i g n o f a M e d i u m - S c a l e H y b r i d I n t e r f a c e " , MA.Sc. T h e s i s , D e p a r t m e n t Of E l e c t r i c a l E n g i n e e r i n g , U . B . C , V a n c o u v e r 8, B.C., May 1967. 

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