Who Gives A 4K About H.265?

The ITU agreed a new video coding standard last Thursday called H.265 / HEVC. Over time this new standard is expected to replace its predecessor and current dominant video codec H.264 (which accounts for over 80 percent of web video today). So what is it, when and where can we use it and why does it matter?


It’s the latest generation video codec from the ITU & ISO/IEC. As such it is pretty much guaranteed the role as the future video codec for mainstream video consumption. Why do we need another codec when H.264 has seen such wide adoption and powers the video world of today? Codecs used in consumer video typically have a simple purpose in life – to reduce the size of a video asset, thus making it more efficient to distribute and store throughout the video ecosystem. They achieve this using ever more sophisticated compression techniques and H.265/HEVC is expected to reduce by half the footprint and bandwidth used when compared to H.264/AVC (which itself reduced by half the bandwidth used compared to its predecessor MPEG-2). This doubling in coding efficiency (and halving of bandwidth) is similar to Moore’s Law in general computing but rather than operating in 18 month cycles these gains have typically occurred in 10 year cycles (H.264 was first ratified ten years ago this coming May).

We need better codecs to keep pace with a significant change in television (and related device) viewing – increasing screen sizes and display resolutions. According to DisplaySearch, the average TV size increased by 2 inches last year and that trend has been gaining pace in recent years. Some analysts are predicting that average set sizes might reach 60″ by 2015. I gawped at the 110″ TVs on the HiSense stand at CES earlier this month. Despite the fact that living room sizes are not keeping pace with this growth, larger screen sizes and higher resolutions even on small screen devices (such as Apple’s Retina displays), put pressure on video resolution as these screens stretch the picture and amplify artifacts and other quality issues.

The advent of mainstream HD viewing has raised the bar significantly in terms of viewer expectations and when you somehow manage to squeeze that new 110″ TV into your living room even Full HD (1080p) wont look very good when you sit a few feet away from it. Thankfully the industry has pre-empted this eventuality and you couldn’t walk more than twenty feet at CES without bumping into a 4K Ultra HD TV. This new standard in video resolution is four times greater than regular old Full HD. Unfortunately this means the associated 4K video assets are also orders of magnitude larger than their Full HD counterparts. Right now there isn’t a lot of 4K content around to worry about, but as the list of such titles grow the problem with distribution becomes very real and without H.265/HEVC to halve the bandwidth and storage 4K is a non-starter.


Like H.264 before it, we can expect to see H.265 support on all manner of video devices from smartphones to TVs. The initial deployments will likely focus on areas where it will make the greatest impact with the lowest constraints – mains powered large high resolution TVs for example. Samsung demonstrated HEVC playback on a 4K prototype TV at CES and deployment is likely to begin in that area first. Over time, once hardware support for H.265 appears in high volume chipsets (as was the case with H.264), this will extend to most devices that playback video (which in itself is an increasing class of devices).


Finally, this is the big question. It took at least 5 years before H.264 support began to take hold and appear in real volume. However, given that H.264 launched in 2003 – before YouTube, smartphones, tablets and connected TVs (a veritable Dark Ages in retrospect) the past, as they say, is not a great guide to the future.

We do know that H.265 is much more computationally expensive than H.264, so while we may see (and in fact already have seen) software encoders and decoders appear we really need to wait for hardware to arrive make playback viable. Before then, playback will incur high CPU load which in turn overburdens many existing device types and drains batteries on mobiles devices. Transcoding all those existing titles from high bit rate sources is non-trivial and won’t be undertaken until sufficient consumption devices exist in the hands of consumers.

My guess is that H.264 will serve us very well until at least late 2014 (and beyond for years of course) when the increasing availability of 4K screens will drive genuine consumer demand. Until then the launch of H.265 is an important milestone and lots of experimenting lies ahead for those of us who work in this fascinating industry.