Linked by lemur2 on Wed 9th Mar 2011 00:18 UTC
Multimedia, AV The WebM project Blog has announced an update release of the VP8 Codec SDK codenamed the "Bali" release. The Bali release was focused on making the encoder faster while continuing to improve its video quality.
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Comment by Gusar
by Gusar on Wed 9th Mar 2011 01:16 UTC
Gusar
Member since:
2010-07-16

Metrics are pretty much useless. Optimizing for PSNR is completely useless, it gives you one big blur. SSIM is better, but not the real deal either. x264 has tunings for both PSNR and SSIM. You know what these tunings do? They turn off options that make the video look good. Do a test yourself, three 2-pass encodes to the same bitrate, first with "--tune psnr", second with "--tune ssim" and third with "--tune film", you'll see.

As long as the libvpx developers focus on metrics, they'll never create a good encoder. Psychovisual optimizations is where it's at. And these psy-opts lower PSNR and SSIM, not raise it (well, AQ raises SSIM compared to no-AQ, but then there's other psy-opts that lower it again).

Edited 2011-03-09 01:18 UTC

Reply Score: 4

RE: Comment by Gusar
by lemur2 on Wed 9th Mar 2011 01:41 in reply to "Comment by Gusar"
lemur2 Member since:
2007-02-17

Metrics are pretty much useless. Optimizing for PSNR is completely useless, it gives you one big blur. SSIM is better, but not the real deal either.

...

Psychovisual optimizations is where it's at.


http://blog.webmproject.org/2011/03/vp8-codec-sdk-bali-released.htm...

Implemented a new "constrained quality" (CQ) data rate control mode. This mode better allocates bits from sections of a video where they can't provide significant visual benefit to sections where they can.
Achieved more consistent high video quality across entire video clips. We now use a better two-pass rate control option that no longer favors early sections of videos.
Greatly improved quality on "noisy" source videos through temporal filtering of alternate reference frames.
Improved visual quality of scene transitions by allocating fewer bits to the transition itself and more to the frame immediately after the transition occurs.


Some of these, especially the last, would not improve the objective quality measures such as PSNR or SSIM much at all. They are "Psychovisual optimizations".

Edited 2011-03-09 01:42 UTC

Reply Parent Score: 4