UBC Theses and Dissertations
Packet loss effects on the quality of MPEG-2 video transported over IP networks Chiu, Daniel
In this thesis, we examine the effects of packet loss on the quality of the MPEG-2 video transported over an IP network. We performed experiments in a video-ondemand testbed network using three constant bit rate MPEG-2 video elementary streams of differing activity levels. We assessed the video quality using the objective peak signal to noise ratio (PSNR) metric and the subjective mean opinion score (MOS) metric. Our results confirmed that the objective PSNR video quality metric is poorly correlated with subjective quality assessments. We found that the activity level of the video influences the subjective MOS video quality assessments but not the objective PSNR quality measurements. The difference in the perceived video quality between the activity streams was found to be attributed to characteristics in the human visual system. In particular, a high temporal frequency decreases the sensitivity of the visual system. We found that slice loss is linearly correlated with packet loss while picture header loss is poorly correlated with packet loss. We also found that slice loss is the dominant factor contributing to the degradation in video quality rather than picture header loss. We found that low packet loss rates translate into much higher frame error rates due to propagation of errors. Finally, we investigated the effectiveness of forward error correction (FEC) using Reed-Solomon coding on the video quality. We found that FEC can increase a stream's packet loss rate tolerance significantly with a small increase in overhead.
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