Presentation on theme: "March 24, 2004 Will H.264 Live Up to the Promise of MPEG-4 ? Vide / SURA March 24. 2004 Marshall Eubanks Chief Technology Officer."— Presentation transcript:
March 24, 2004 Will H.264 Live Up to the Promise of MPEG-4 ? Vide / SURA March 24. 2004 Marshall Eubanks Chief Technology Officer
March 24, 2004 A Brief History - ISO MPEG 1 and 2 were a real success story in video broadcasting. –Early 1990s 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.
March 24, 2004 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.
March 24, 2004 A Brief History - Contd MPEG-4 is a late 1990s 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!).
March 24, 2004 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
March 24, 2004 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
March 24, 2004 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 (VOPs), 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.
March 24, 2004 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
March 24, 2004 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 codecs 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.
March 24, 2004 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.
March 24, 2004 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.