[theora] A comparison of VP3, and two MPEG-4 variants
blibblelibby at black-market-babies.com
Tue Mar 25 06:56:45 PST 2003
On Tuesday, March 25, 2003, at 12:42 AM, Dan Miller wrote:
>>> And as a final note, PSNR is really a terrible way to judge codec
>>> quality. Among many other sins, it completely fails to penalize
>>> codecs that stomp on frequency response rather than try to
>>> the spectral nature of an image. (TBH, the present VP3 encoder is
>>> guilty of this, though a future encoder could be much smarter).
>> I guess that is true. I have not done any studies of PSNR...
>> I am aware
>> that you know more about this than I will ever know. Do you
>> know of any
>> test that that a computer do that take those into account? I would be
>> very happy if you could point me in the direction of a better test.
> see http://www.its.bldrdoc.gov/n3/video/vqmsoftware.htm
> the ITS solution is a front-runner for standardization by ITU/VQEG.
> It does substantially better than PSNR, especially at lower datarates
> where PSNR really breaks down.
> Their software can be downloaded free but only for eval and research
> (ie 'non-commercial' products). It is also unfortunately heavily
> patented. Therefore, while Xiph will probably not use it as part of
> their core development, it seems perfectly OK for some independent
> individual to use it to do an evaluation and report the results.
> Their tool is PC or Linux only, and imports AVI's but not QT files.
> There are several competing systems, the best 2 or 3 of which
> apparently work according to similar principles and have shown very
> similar results in comparisons with extensive subjective tests on a
> wide range of materials. I suspect that once this stuff is
> standardized, PSNR will finally be relegated to a useful but clearly
> insufficient tool for objective quality measurement.
Thank you. I don't have much of PC at the moment, but I will be
borrowing one soon. I will try to use this. It won't be a problem to
move the video into an AVI.
Do you have any URLs for the competing systems?
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