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Will H.264 Live Up to the Promise of MPEG-4 ?

Will H.264 Live Up to the Promise of MPEG-4 ?. Marshall Eubanks Chief Technology Officer. Vide / SURA March 24. 2004. A Brief History - ISO. MPEG 1 and 2 were a real success story in video broadcasting. Early 1990’s compression technology Published 1993 & 1995

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Will H.264 Live Up to the Promise of MPEG-4 ?

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  1. Will H.264 Live Up to the Promiseof MPEG-4 ? Marshall Eubanks Chief Technology Officer Vide / SURA March 24. 2004

  2. A Brief History - ISO • MPEG 1 and 2 were a real success story in video broadcasting. • Early 1990’s compression technology • Published 1993 & 1995 • Comes from the MPEG working group of the ISO • Was not designed with latency or packet loss in mind • MPEG-2 is ubiquitous in broadcast digital video - on air, cable, DVD, HDTV, etc.

  3. A Brief History - ITU • At the same time, and using similar principles, the International Telecommunications Union (ITU) Low Bitrate Coding Experts Group came out with the H.261 and H.263 standards • H.261 published 1993 • H.263 published 1998 • These standards were designed for Video Conferencing using TDM / ISDN • Used in most legacy videoconferencing systems.

  4. A Brief History - Cont’d • MPEG-4 is a late 1990’s update to MPEG-4 • Published 1999 • At the same time, the ITU was working on H.263+ / H.263++ / H.26L standard extensions. • In 2001, the ITU VCEG and the ISO MPEG joined forces • H.264 was published in 2003. It is also MPEG-4 Part 10 (not version 10!).

  5. MPEG-X & H.26X • All of these standards have similar frameworks • The fundamental basis for compression is the macroblock (16 x 16 pixels), arranged into Slices. • All allow the use previous (or future!) frames to predict the current frame (or macroblock) • Encoding is thus a representation of the prediction and the residual from the prediction. • All allow for motion compensation to improve interframe prediction. • All use block based transforms and quantization to low pass filter the residual visual information

  6. Some ways Video Compression Is Improved • Finer grained and better motion prediction • 1/2 pixel (MPEG-4) to 1/4 pixel (H.264) • Variable block-sized motion compensation • The block size can vary depending on the complexity of the scene • Minimum block is 8x8 pixels for MPEG-4, 4x4 for H.264 • Intra Prediction • Use other parts of the current frame to improve the prediction of the current macroblock

  7. MPEG-4 Complications • MPEG-4 is a very complicated standard • 19 separate video profiles • Support for rectangular frames, arbitrarily shaped objects, synthetic and 3-D mesh objects, multiple Video Object Planes (VOP’s), semi-transparent objects, etc. • The complexity is so great that the Internet Streaming Media Alliance (ISMA) has come out with its own basic profile for MPEG-4 for streaming • MPEG-4 requires License fees • Payable to MPEG-LA • The uncertainty around this has really hindered the introduction of MPEG-4 for streaming.

  8. What does H.264 offer (technical) • H.264 has only 3 profiles and only supports rectangular images. • H.264 offers a number of technical advantages even over MPEG-4 • Finer grained motion prediction and adaptive block sizes. • Integer Transforms. Previous standards use the Discrete Cosine Transform (DCT), which requires real arithmetic. Since computers approximate real arithmetic, the inverse transform is inexact. • H.264 uses an integer approximation to the DCT, which is faster and has an exact inverse. • Deblocking filters - to remove the blocking artifacts common to macroblock based encoding standards. • Multiple reference pictures • A list of reference pictures can be stored for use by the encoder / decoder

  9. H.264 for Streaming and VideoConferencing • Multiple reference pictures are very useful for videoconferencing • You can send a high quality copy of the background scene for the codec’s use. It does not have to only use the most recently transmitted image for prediction, but can use a reference picture. • Similarly, the codec uses a sliding window to keep old decoded images, also for possible predictive use. • Packet loss resiliency is substantially improved. • The codec can send use “redundant” coded pictures for use if a frame is missing. • Frames & slices can be mixtures of inter and intra encoded macroblocks. • This mean that the old Group of Pictures organization can be dropped - there is no need to send repeated “I frames” • Packet losses can be corrected using the redundancy inherent in the intra-encoded macroblocks.

  10. H.264 Licensing • The H.264 baseline profile was designed not to require licenses or royalty payments. • The draft was compared with existing patents not in the H.264 pool, and was modified to engineer around the claims of these patents • While there are no guarantees in patent laws (and IANAL), it seems reasonable that there will not be a required royalty payment for the baseline profile. • The MPEG-4 licensing controversy has clearly hindered the adoption of the codec.

  11. Conclusions • MPEG-4 and H.264 offer a substantial improvement over previous video codec standards. • H.264 tailors these improvements for videoconferencing, and (hopefully) avoids the MPEG-4 licensing issues. • H.264 is seeing rapid adoption in videoconferencing. Will it become a major standard for other uses - streaming, storage, etc.? • Only time will tell.

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