Friday, September 4, 2015

HEVC, AOMedia, MPEG, and DASH

Ultra-high definition (UHD) displays are available for quite some time and in terms of video coding the MPEG-HEVC/H.265 standard was designed to support these high resolutions in an efficient way. And it does, with a performance gain of more than twice as much as its predecessor MPEG-AVC/H.264. But it all comes with costs - not only in terms of coding complexity at both encoder and decoder - especially when it comes to licensing. The MPEG-AVC/H.264 licenses are managed by MPEG LA but for HEVC/H.265 there are two patent pools available which makes its industry adoption more difficult than it was for AVC.

HEVC was published by ISO in early 2015 and in the meantime MPEG started discussing about future video coding using its usual approach of open workshops inviting experts from companies inside and outside of MPEG. However, now there’s the Alliance for Open Media (AOMedia) promising to provide "open, royalty-free and interoperable solutions for the next generation of video delivery” (press release). A good overview and summary is available here which even mentions that a third HEVC patent pool is shaping up (OMG!).

Anyway, even if AOMedia’s "media codecs, media formats, and related technologies” are free like in “free beer” it’s still not clear whether it will taste anything good. Also, many big players are not part of this alliance and could (easily) come up with some patent claims at a later stage jeopardising the whole process (cf. what happened with VP9). In any case, AOMedia is certainly disruptive and together with other disruptive media technologies (e.g., PERSEUS although I have some doubts here) might change the media coding landscape, not clear whether it will be a turn to the better though...

Finally, I was wondering how does this all impact DASH, specifically as MPEG LA recently announced that they want to establish a patent pool for DASH although major players have stated some time ago not to charge anything for DASH (wrt licensing). In terms of media codecs please note that DASH is codec agnostic and it can work with any codec, also those not specified within MPEG and we’ve shown it works some time ago already (using WebM). The main problem is, however, which codecs are supported on which end user devices and how to access them with which API (like HMTL5 & MSE). For example, some Android devices support HEVC but not through HMTL5 & MSE which makes it more difficult to integrate with DASH.

Using MPEG-DASH with HMTL5 & MSE is currently the preferred way how to deploy DASH, even the DASH-IF’s reference player (dash.js) is assuming HTML5 & MSE and companies like bitmovin are offering bitdash following the same principles. Integrating new codecs on the DASH encoding side like on bitmovin’s bitcodin cloud-based transcoding-as-a-service isn’t a big deal and can be done very quickly as soon as software implementations are available. Thus, the problem is more on the plethora of heterogeneous end user devices like smart phones, tablets, laptops, computers, set-top-boxes, TV sets, media gateways, gaming consoles, etc. and their variety of platforms and operating systems.

Therefore, I’m wondering whether AOMedia (or whatever will come in the future) is a real effort changing the media landscape to the better or just another competing standard to choose from … but on the other side, as Andrew S. Tanenbaum has written already in his book on computer networks, “the nice thing about standards is that you have so many to choose from.”
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