The State of Protocols and Formats 2014
To deal with 4K content, from streaming to broadcast, the MPEG and ITU standards bodies both ratified a newer codec. Based on AVC, this new High Efficiency Video Coding codec (HEVC, but also known as H.265 or MPEG-H Part 2) has an additional set of parameters.
One part of these new parameters is an ability to encode certain portions of a video frame at greater detail than others. With AVC, as with the MPEG-2 codec, content is assessed across multiple frames (using interpolation, motion vector estimation, and additional algorithms) to determine where content may be shown in both prior and subsequent frames.
This multiframe compression, known as inter-?frame compression, allows the encoding system?to markedly decrease the size of a group of pictures that can range from less than a second to several seconds in length. Content within the frames that does not change, such as the background of an image, can be referenced from key frame to key frame, often with dramatic storage and transport bitrate savings.
The problem with interframe compression, however, has been that it relies on compressing rather large portions of a video frame via a technique called a macro block. HEVC looks to solve the problem by allowing each macro block to be further divided into a smaller set of blocks to increase detail in a particular part of the frame. A practical example may be a scoreboard with detailed lettering that takes up a very small portion of the frame; without the ability to further refine the macro block size, details such as words on the scoreboard could inadvertently not be rendered.
The downside of HEVC, however, is the increase in raw computing power needed to render the increased number of refined areas. It turns out that the additional processing on SD content or even lower-end HD content (such as 720p) doesn’t result in appreciable storage or bandwidth savings, even if it does somewhat increase the perceived quality of the video. As such, HEVC will be better suited to use with True HD (1080p) and Ultra HD (4K) content.
Alain Pellen, Thomson Video Network’s marketing director for OTT and web TV solutions, noted during the 2013 Streaming Media Forum in London that “HEVC halves the H.264 bitrate and addresses Ultra HD,” so the industry expects to put its effort behind H.265 instead of looking to continually improve H.264 incrementally.
The DASH Industry Forum has helped add some clarity around how HEVC and DASH would work together, publishing a draft guideline (version 0.92 as of September 2013) of the key implementation points between HEVC and DASH (go2sm.com/dash092). As of this writing, the final set of guidelines is set to be published by Feb. 10, 2014.
MPEG LA, the licensing and patent pool group responsible for MPEG-2 and H.264 licenses, also added a bit more clarity around the licensing implications of HEVC. There had been some uncertainty as to royalty payments, as Jan Ozer reported back in April 2013, noting that while H.264 “involved a single group of patent holders administered by MPEG LA, it appears that some HEVC patent holders want to pursue royalties outside of a patent group, which will make it more challenging for HEVC users to license the technologies.”
Fortunately, saner heads prevailed, and MPEG LA announced on Jan. 11, 2014, that it had a set of guidelines that “a group of 25 companies have agreed on HEVC license terms expected to issue as part of an HEVC Patent Portfolio License in early 2014.” Hopefully, the final terms will be set before the mid-April National Association of Broadcasters show in Las Vegas.
VP9 and WebM
Not be outdone, Google used the 2014 CES to make a push into the Ultra HD market, using a new version of the codec it acquired from On2 Technologies a few years ago.
Shortly after VP8 was announced, On2 went radio silent and wouldn’t hand out its codec tools to analyze the company’s claims that it was better than H.264/AVC, although it had eagerly done so with the previous codec, VP7.
The reasoning, it later turned out, was that Google was in talks to acquire On2’s technology assets and asked the company to hold release of VP8 until it could be let out into the wild under the Google brand. That process took longer than anyone would have liked, and Google failed to get traction in the marketplace with VP8, rebranded as WebM, partly due to the same types of licensing issues it had faulted MPEG LA for with AVC.
Fast-forward a few years, and WebM is available natively in one browser -- the desktop version of Google Chrome, even though the Android version of Chrome opted to natively support H.264 and HLS -- but that hasn’t stopped Google from pushing forward with advances to the core codec.
General availability of VP9 started in June 2013, with limited traction. Yet, it turns out that Ultra HD (4K) may just be the sea change in the industry that Google needs to catch the encoding wave and spur VP9 adoption. As recently as January 2014 at CES, Google paired VP9 with Ultra HD content, firmly attaching itself to the Ultra HD bandwagon amid greater interest in lower-priced consumer Ultra HD monitors.
Google is also hard at work on the hardware front, with webmproject.org noting on the last business day of 2013 that it had completed the VP9 decoder RTL (register transfer level, codename G2) and launched in WebM.
“RTL has already been shipped to a number of SoC vendors developing chipsets for tablets and smart TVs, all preparing to ship silicon in 2014,” the webm project.org site states.
In addition, further enhancements to the codec continue: One recent example is the uncovering of a rate distortion bug, which, according to webmproject.org, “hurt lossless mode and potentially some other very low Q encodes.” Subsequent tests, after the bug fix, yielded “gains averaging about 8 percent for lossless encodes with some clips as high as 25 percent.”
At the end of 2013, Google announced the hardware architecture requirements for VP9/WebM.
This is just a small snapshot of the current state of protocols and formats, many of which will have made advances even in the time between writing and publication of this article. If you see a protocol or format that we’ve not covered, feel free to email the editor or myself, and we’ll do an update on StreamingMedia.com.
This article appears in the 2014 Streaming Media Sourcebook.
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