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H.264 - The Advanced Videoconference Codec
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H.264 received Final Draft status on March 28, 2003 by the Joint Video Team (JVT), a committee of Moving Picture Experts Group (MPEG) and International Standards Organization/International Telecommunications Union (ISO/ITU). Final ratification of H.264 by the ITU happened on May 30th. H.264 is also known as MPEG 4 part 10.
The bottom line is that H.264 enables videoconferences to connect at half the bandwidth and still retain the same quality or it will deliver twice the quality at the same bandwidth normally used.
What is H.264?
A new video encoding and decoding scheme has been added as a standard under the International Telecommunications Union's (ITU) H.320 and H.323 umbrella for low bandwidth videoconferencing over ISDN and IP. This new codec provides near broadcast quality video, in part, by supporting 60 fields per second (30 full frames) and an advanced method of reducing, if not eliminating, the pixelization we often see when using H.261 or H.263 video codecs when there is a lot of motion or scene changes.
The ITU, along with Internet streaming and other standards organizations, formed a "Joint Video Team" (JVT) to come up with a common format codec for both MPEG users and videoconferencing users. The resulting new standard codec is know as JVT/AVC (Advanced Video Coder). It is known by the MPEG industry at MPEG 2 Part 10 and by the ITU and the videoconferencing industry as H.264.
H.263, the codec in use the past several years, supports 30 frames per second video. In television video, each frame has two interlaced fields. Prior to compressing, one field is tossed aside (every other line) by H.263 to produce 30 frames per second video at the narrow bandwidths used in videoconferencing. Thus, each compressed video frame corresponds to only one of two input video fields. The result is a somewhat lower video resolution quality of 352x288 pixels or "video pixelization."
The H.264 protocol improves the video resolution quality in the H.323 protocol suite by encoding and transmitting two interlaced fields for each frame. That is 30 frames per second and 60 fields per second (instead of only 30 fields per second of H.263). This process allows us to present decoded video that is immensely more fluid and lifelike. The result of this enhancement is a substantially higher resolution quality that approaches or matches MPEG-2 quality at a 64% lower bandwidth cost.
H.264 also handles the encoding of the pixel blocks more efficiantly than H.263, practically eliminating the tiling or pixellation seen on videoconferences today when there is a "scene" change or a lot of motion.
Wisconsin VCS H.264 Research and Demonstrations:
Since May 5th, they have been demonstrating H.264 video to many of their Wisconsin videoconference users and potential users. During the demonstrations, they compared H.264 to H.263 in side-by-side projected images. They also compared H.264 with MPEG 2 in side by side images.
At 384K and 768K, there is a remarkable difference in the video quality as perceived by the human eye. They have also compared H.264 at 384K against H.263 at 768K and even then found, though more subtle, a difference in the video quality.
They have also compared side by side, H.264 at 768K with MPEG 2 at 4 Meg. The H.264 video is amazingly similar in quality to the MPEG 2 signal. Some of the fine lines in the video were just a bit more jagged in the H.264, which was not noticed by many of those attending the demos.
These demonstrations were conducted over a lab simulated network configured similar to the WiscNet backbone with two member LANs connected to the edge. The codecs used were Polycom FX's for the H.263 video and two Polycom iPower 9000 codecs for the H.264 video. They also used a Minerva MPEG encoder and a decoder to provide the MPEG 2 video.
Test video is from a DVD movie with a lot of motion. The video is fed into the three codecs at Site B. The three codecs are each connected to the same model codec at Site A over the lab network (FX to FX, 9000 to 9000, Minerva to Minerva). At Site A, they projected the decoded H.263, H.264 and the MPEG 2 side by side.
Will my legacy Polycom unit support H.264?
We consider endpoints with H.264 compatibility essential to our endpoint recommendations. The protocol will alleviate current H.323 resolution quality perceptions, provide more bandwidth for multiple, concurrent videoconferences and permit interconnection with the substantial deployment of non-H.264 compatible H.323 systems.
We understand that Polycom is developing a software upgrade for the FX, EX and 4000 models of their codecs to support H.264 to be available in 2004. Older models, such as the 512 and 128 will not be upgradable. We have no word on the ViaVideo at this time.
Where can I learn more about H.264?
~Exerpts for the material on this page have been graciously contributed by Wisconsin VCS Videoconference Services
For comments regarding this site, please email Debby Thompson at debbyt@ncesd.org
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