The Case for VP9
Google’s VP9 plays on about 60% of browsers today, as compared to 0% for HEVC, it delivers similar quality to H.264 at 50-60% of the data rate, and ultimately it may be the only UHD codec that plays on Firefox and Opera. And while VP9 may play only a minor role in broadcast markets, mobile, or OTT, it may be an essential component for reaching the traditional desktop/notebook market.
Let’s start with quality. There have been three recent comparisons, including my own. The first is “Comparison of compression efficiency between HEVC/H.265 and VP9 based on subjective assessments,” by Martin Rerabek and Touradj Ebrahimi. Here, the authors concluded that, “objective-based measurements shows that HEVC achieves average bitrate savings of 39.6% versus AVC and 35.6% versus VP9, [while] subjective scores show an average bitrate reduction of HEVC by 52.6% in comparison to AVC and 49.4% in comparison to VP9.” In other words, HEVC was significantly better than VP9, which really was no better than H.264.
Iain Richardson, founder of Vcodex and author of four video compression books, produced the second comparison. Though Richardson’s tests were much less extensive, they did involve subjective ratings by ten subjective non-expert viewers. He concluded, “At the higher end of the quality scale (i.e. lower compression), both HEVC
and VP9 achieve a similar viewing quality to H.264 with a 40-45% reduction in file size.” In other words, relative parity.
For my tests, which I’ll document in a future Streaming Media article, I asked Google to prepare their encodes for me, as did the supplier of an embedded HEVC solution. I also prepared another set of test clips using a highly respected enterprise encoder that used the x265 codec. I computed the VQM scores using the Moscow University Video Quality Measurement Tool (which I reviewed for the European Edition of Streaming Media magazine) and verified the scores with my own subjective comparisons. My results more closely matched Richardson’s; in fact, VP9 produced slightly better quality than HEVC in eight of nine test cases.
I have more work to do on these comparisons, both to make sure I’m comparing apples to apples quality-wise and to assess encoding time and the required playback horsepower. But I’m reasonably confident that, at the end of the day, the quality produced by VP9 will be similar to that offered by HEVC.
More importantly, as we transition away from Flash and towards HTML5, it’s likely that VP9 will be the only UHD codec that plays in Firefox and Opera. Today, Firefox, Opera, and Chrome—which together comprise about 60% of browser share according to w3counter.com—all play VP9, while no browsers play HEVC. Microsoft has announced HEVC playback support for Windows 10, which won’t ship until mid to late 2015. Though Apple and Google now offer HEVC on their latest mobile OSs, there have been no announcements regarding Safari or Chrome, though I would expect both to support HEVC playback sometime in 2015.
However, I think it’s very unlikely that Firefox, with 17% of overall browser market share, will ever license HEVC. They never licensed H.264 (though some versions of Firefox could grab an H.264 decode from the operating system) or via Flash. With Microsoft only including HEVC decode in Windows 10, there will be hundreds of millions of computers without OS-based HEVC decode for many years to come. And while Adobe has announced that it will support HEVC playback in Primetime, it has not announced support for HEVC decode in Flash Player. So it’s likely that neither Firefox nor Opera will ever natively play HEVC—VP9 will be your only option.
There certainly will be some speed bumps on the transition from Flash to HTML5, particularly for those monetizing their videos and protecting them with DRM. But the transition will happen, and as things look now, VP9 may play a much bigger role than HEVC in that transition, and much sooner.
[This article appears in the January/February 2015 issue of Streaming Media magazine as "The Producer's View: The Case for VP9"]
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