[theora] A comparison of VP3, and two MPEG-4 variants

Colin Mckellar 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:

> ...
> [dan:]
>>> 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
>> approximate
>>> the spectral nature of an image. (TBH, the present VP3 encoder is
>>> guilty of this, though a future encoder could be much smarter).
> [colin:]
>> 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?

Thank you


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