HEVC : is it really twice as good as H.264?

On the left, a close up from 'Kristen and Sara' (720p resolution), encoded at 800kbps using x264. On the right, the same clip encoded at 420kbps using HEVC's HM10 test model encoder.
If HEVC is really twice as good as H.264, then the quality of the right-hand clip should be as good as, or better than, the left-hand clip. Visit
my blog for some further examples and judge for yourself.

HEVC : The draft standard

The new standard under development by ISO MPEG and ITU-T VCEG, HEVC, was approved by the ITU-T on 25th January 2013. You can download a draft version of the High Efficiency Video Coding (HEVC) standard from the JCT-VC document site.

Draft Version 10 of the HEVC specification can be downloaded here. Alternatively,
go to the JCT-VC document site:http://phenix.int-evry.fr/jct/

The document is JCTVC-L1003, available in All Meetings / Geneva.

How Efficient is HEVC?

The new High Efficiency Video Coding (HEVC) / H.265 standard is expected to be more efficient than its predecessor, H.264 Advanced Video Coding. Just how much better it will perform is a crucial question. Will it be enough of an
improvement to justify widespread industry adoption of the new standard?

Bin Li, Gary Sullivan and Jizheng Xu published a performance comparison between H.264/AVC and Working Draft 4 of HEVC in November 2011. You can find the full document and results here:

Document JCTVC-G399

Table 4 of the document compares the compression performance of the HEVC test model ("HM") and the H.264 test model ("JM"). 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).

This means that the HEVC codec can achieve the same quality as H.264 with a bitrate saving of around 39-44%.

HEVC is still under development and we might expect to see a further increase in performance from future versions of the draft standard.

High Efficiency Video Coding

High Efficiency Video Coding (HEVC) is a new Standard under development by the ISO and ITU-T. The Moving Picture Experts Group (MPEG) and Video Coding Experts Group (VCEG) have set up a Joint Collaborative Team on Video Coding (JCT-VC)
with the aim of getting the new standard ready for publication in early 2013. It's likely to be published jointly as a new MPEG standard and a new ITU-T standard, possibly H.265.

The HEVC Test Model

Following the JCT-VC and MPEG meeting in October 2010, a Test Model for HEVC, HM1, was specified. The Test Model defines two broad categories of video coding tools, for (a)
High Efficiency and (b) Low Complexity applications.

What's in the Test Model?

The main components are as follows:

Coding unit: Block sizes from 8x8 to 64x64 in tree structure
Transform: Quadtree structured block size from 4x4 to 32x32 samples
Intra prediction: Up to 34 intra prediction directions
Interpolation: 6- or 12-tap interpolation filter, down to 1/4-sample
Motion prediction: Advanced motion vector prediction 
Entropy coding: CABAC or Low Complexity Entropy Coding (LCEC)
Loop filter: Deblocking filter or Adaptive Loop Filter (ALF)
Precision: Extended precision options

Many coding tools have been scheduled for further investigation and may be incorporated into the Test Model if they offer suitable compression gains.

How will it compare to H.264/AVC?

Current indications are that the new standard could provide 2x better video compression performance (i.e. around half the bitrate for a similar quality level) at the expense of significantly higher computational complexity, compared
with H.264/AVC.

When will it be finished?

The timescale for completing the HEVC standard is as follows: 
February 2012: Committee Draft (complete draft of standard)
July 2012: Draft International Standard
January 2013: Final Draft International Standard (ready to be ratified as a Standard)

Where can I find out more?

JCT-VC Meeting Documents : download JCTVC-C405 for a summary of the HEVC test model HM1.

High Efficiency Video Coding