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BBC Confirms 50% Bitrate Savings For H.265/HEVC Vs H.264/AVC (bbc.co.uk)

Posted by Soulskill on from the just-a-half-bit-better dept.

An anonymous reader writes: A research team from the BBC has done a series of tests to confirm earlier computations showing a ~50% savings in bit rate for H.265/HEVC compared to video using H.264/AVC at comparable quality. "The subjective tests used a carefully selected set of coded video sequences at four different picture sizes: UHD (3840x2160 and 4096x2048), 1080p (1920x1080), 720p (1280x720) and 480p (832x480), at frame rates of 30Hz, 50Hz, or 60Hz. The video content was chosen to represent diverse spatial and temporal characteristics, and then coded using HEVC and AVC standards at a wide span of bit rates producing a variety of quality levels." Here is the full published analysis. "The tests confirmed the significant compression efficiency improvements achieved in HEVC, verifying the results previously reported using objective quality metrics (PSNR based methods)." The team did not test against VP9, which is shaping up to be an impressive standard as well.

4 of 110 comments (clear)

  1. "comparing" video CODEC quality is very hard... by kbonin · · Score: 5, Interesting

    I've played in this space in a former position. Interesting lessons learned:
    - PSNR is nearly worthless: An image with almost the same score can look terrible. Not all the time, but enough of the time.
    - The only quantitative test I found that worked reliably was an old analog Tektronix PQA500 (lots of work to use for digital CODEC.)
    - Management didn't like the PQA data (it said our product was terrible), decided to use PSNR data (product is great!)
    - Customers fixed this discrepancy and product line failed spectacularly (due to video quality, surprise!)
    - I never could find any published information sufficient to recreate the Tek PQA algorithm.

    1. Re:"comparing" video CODEC quality is very hard... by Fwipp · · Score: 5, Informative

      Which, if you click through, is why the study performed subjective tests; by asking viewers to rate the quality of several videos at several bitrates on a 10-point scale in a series of tests. They found that PSNR systematically underestimated the perceived quality of H.265 (relative to H.264).

  2. vs H.264 yes by SirMasterboy · · Score: 5, Informative

    50% bitrate reduction vs H.264 sure, but not vs x264 which is the current gold standard for HQ video compression.

    It's like comparing a new audio codec to the original fraunhofer MP3 encoder. LAME on the other hand is a significantly better MP3 encoder like x264 is a better H.264 encoder.

    My own compression testing between HEVC and x264 show that at verty low bitrates, yes HEVC is better, but only at bitrates below what I would normally use and what I would consider "quality" encodes.

    When you compare say a 10GB x264 encode of a full-length BluRay film, even 8GB for the HEVC does not provide an equal or superior copy.

  3. Re:Unbiased source? by tlhIngan · · Score: 5, Informative

    The benefit for them is that they can reduce costs by reducing the bitrate, and claim not to have reduced picture quality. They have done it before - when HD broadcasts started they were around 18Mb/sec IIRC, but were later reduced to less than half that (average per channel, they actually balance about 18Mb/sec between two channels in a kind of VBR system). They claimed that the picture didn't suffer but it very clearly did, and it's now rather poor.

    They are under immense financial pressure, and reducing bitrate (and picture quality) allows them to save something else, someone else's job.

    The problem is, HEVC is expensive. While the MPEG-LA made h.264 the way it is by making streaming free (if the viewer doesn't pay) and offering caps to the maximum license fees, thereby encouraging big users (Cisco, Apple, Microsoft, Netflix, etc) to switch to h.264 and merely pay the cap every year

    Of course, MPEG-LA wanted to encourage the switch to HEVC by offering the same terms, and several patentholders balked which is why they pulled out of the MPEG-LA pool and created the HEVC Alliance which licenses without a cap, without free streaming (they want some money per HEVC stream), meaning the money you save in bandwidth might go straight to licensing fees.

    And I'm sure the BBC streams under h.264 were basically cost-free since the streams were available at no charge (granted, you paid with your TV license, but the MPEG-LA doesn't count that), so switching will create costs.