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UBC Theses and Dissertations

Efficient coding and mapping algorithms for software implementation of a real-time H.263+ compliant low bit rate video coder | Erol, Berna

Abstract

The growing interest in video coding applications led to the development of video coding standards. Several successful standards have emerged, such as the ITU-T H.261, H.263, ISO/EEC MPEG-1 and MPEG-2. ITU-T recently announced its latest low bit rate video coding standard, the H.263 Version 2, also known as the H.263+ standard [25]. While this new low bit rate video coding standard provides better compression performance levels than those of the former ones, it is more complex and is more computationally, demanding. In this thesis, we develop coding and mapping algorithms that improve the video coding speed performance, making a reality the software implementation of interactive real-time low bit rate video coding on the Pentium MMX general purpose processor. First, using statistical properties of low resolution and slowly varying video sequences, we manage to significantly reduce the computation times of the most computationally intensive components of video coding, particularly the DCT, the IDCT, quantization and half pixel motion search. We also map some of the SIMD (Single Instruction Multiple Data) oriented functions onto Intel's M M X architecture. The developed algorithms are implemented using our public-domain H.263+ encoder/decoder software [45]. After the algorithmic optimization and the M M X mapping, the resulting H.263+ video encoder implementation runs approximately 3 times faster than the original unoptimized public-domain encoder implementation. Moreover, our optimized H.263+ compliant video coder implementation can encode/decode more than 15 frames of a QCIF (176x144) video sequence per second without sacrificing video reproduction quality.

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