When Will H.265 HEVC Arrive and What Will it Mean for MPEG DASH?
Last year's MPEG standards buzz was around DASH (dynamic adaptive streaming over HTTP) which provides a standardized way to segment H.264-based MP4 files for fragmented delivery. This year's end-of-year buzz may very well be around the high-efficiency video coding (HEVC) codec set to replace H.264.
Known as H.265, the specification is currently in its draft stage, with the most recent draft being released last week. Hot on the heels of MPEG LA's call for essential HEVC patents, which we covered last month, the newest H.265 draft -- Draft 6 -- is now available for your reading pleasure in a Zip file.
Draft 6 appears to be solid enough, addressing a number of outstanding questions from previous drafts, so we suspect MPEG is nearing the end of its draft versions and setting the stage for an early 2013 release of the codec.
One question, naturally, is how much more efficient will H.265 be versus H.264. In much the same way that AAC doubled the efficiency of MP3, it appears that H.265 is set to double the efficiency of H.264, especially when it comes to mobile delivery.
Iain Richardson, a video compression specialist who leads Vcodex and has authored several books on video coding technologies, mentions in a recent blog post that H.265 comparative testing has been going on for almost a year.
"Bin Li, Gary Sullivan and Jizheng Xu published a performance comparison between H.264/AVC and Working Draft 4 of HEVC in November 2011," writes Richardson. Sullivan is considered by many to be the father of H.264, as he sat on both the ITU and MPEG working committees, bringing together MPEG 4 Part 10 and H.264 to what is jointly known as Advanced Video Coding (or AVC).
"On average, HEVC out-performs H.264 by 39% for random access scenarios (e.g. broadcast) and by 44% for low delay scenarios (e.g. video calling)," writes Richardson. "This means that the HEVC codec can achieve the same quality as H.264 with a bitrate saving of around 39-44%."
Not too shabby for output from an early draft spec, and it's quite possible we'll see significant optimization before the final draft is released for ratification sometime in late 2012. Download the full outcome of testing done by Li, Sullivan, and Xu.
So how does this move to H.265 impact DASH? Often overlooked in coverage of the DASH specification is the fact that DASH is codec agnostic, and to a certain extent, transport-stream protocol agnostic. This was done primarily to allow Apple a way to encapsulate H.264 in Apple's flavor of the MPEG-2 Transport Stream protocol while still allowing Adobe, Microsoft, and others to use MP4 elementary streams.
This codec-agnostic approach means that H.265 will be able to seamlessly integrate in to a DASH workflow, provided that end-user DASH players are capable of decoding H.265 video. For more on DASH, read "What is MPEG DASH?" and, for more on H.265, look for Jan Ozer's upcoming article titled "What is H.265?"
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