Sunday, March 1, 2009

Not All Packets Are Equal

... is the title of a IEEE Internet Computing article comprising two parts.

Part 1 - Streaming Video Coding and SLA Requirements - describes the some Quality of Service (QoS) characteristics (i.e., delay, jitter, packet loss) and details some of the coding principles adopted in MPEG standards (and btw. others): subsampling, intra coding, inter coding, blocks, macroblocks, slices, frames, group of pictures (GoPs), decoding order vs. transmission order, and MPEG encapuslation within IP.

Part 2 - The Impact of Network Packet Loss on Video Quality - highlights the impact that different durations of IP packet loss have on the Quality of Experience (QoE) for IP-based video streaming services. It describe the visual impairments that result from such packet losses and present the results of testing and analysis to compare impairments for different loss durations for both MPEG-2-encoded standard and high-definition services.

Both arcticles are a very good starting point to get an overview of video coding and how to stream video data over IP-based networks. However, it mainly focuses on MPEG-2 and only mentions the current state-of-the-art codec, namely Advanced Video Coding (AVC). There are already papers available that investigate the impact of packet loss on video quality for AVC.

Nevertheless, the two papers are worth reading, written in an easy-to-read style, and also suitable for an audience not so familiar with video coding and transmission issues. Finally, it seems that there's another article planned in this series as indicated in the last sentence:
"In a future article, we hope to compare different network technology approaches for minimizing and recovering from video packet loss."
I'm looking forward to that ... (and please, bring more on AVC) -- thanks!

References
  • J. Greengrass, J. Evans, A. C. Begen, "Not All Packets Are Equal, Part I: Streaming Video Coding and SLA Requirements," IEEE Internet Computing, vol. 13, no. 1, pp. 70-75, Jan./Feb. 2009
  • J. Greengrass, J. Evans, A. C. Begen, "Not All Packets Are Equal, Part 2: The Impact of Network Packet Loss on Video Quality," IEEE Internet Computing, vol. 13, no. 2, pp. 74-82, Mar./Apr. 2009
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