H什么时候.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.
被称为H.265, the specification is currently in its draft stage, with the most recent draft being released last week. 紧跟在…之后 MPEG LA的 call for essential HEVC patents, which we 上个月报销，最新的H.265 draft -- Draft 6 -- is now available for your reading pleasure 在Zip文件中.
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对H.264. In much the same way that AAC doubled the efficiency of MP3, it appears H.265 is set to double the efficiency of H.264, especially when it comes to mobile delivery.
伊恩•理查森, a video compression specialist who leads Vcodex and has authored several books on video coding technologies, 在一个 最近的博客 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 由李、沙利文和徐完成.
那么这个是怎么变成H的呢.265冲击仪表板? Often overlooked in coverage of the DASH specification is the fact that DASH is codec agnostic, 在某种程度上, transport-stream protocol agnostic. This was done primarily to allow Apple a way to encapsulate H.264 in 苹果的 flavor of the MPEG-2 Transport Stream protocol while still allowing Adobe, 微软, and others to use MP4 elementary streams.
This codec-agnostic approach means 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视频. 有关DASH的更多信息，请阅读 “什么是MPEG DASH ??" 更多关于H.265, look for Jan Ozer's upcoming article titled "What is H.265?"
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