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Old 29th May 2003, 19:09   #54  |  Link
Acaila
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Join Date: Jan 2002
Location: Netherlands
Posts: 1,529
Quote:
Originally posted by JimiK
Did you compare the quality of the clips when you confirmed Didée's test? Because as we all know: higher PSNR does not necessarily mean better visual quality (that's why they used another method called JNI in a test by the german computer magazin c't. JNI should also consider the human visual system). Of course I know that Didée is here for a long time and I don't doubt that this matrix is great, but it just makes me wonder why.
I quickly scanned through them and couldn't see any differences, however I doubt anyone could see the difference between e.g. a PSNR of 45 and a PSNR of 45.5 though (yes I know it's possible, but I couldn't do it). I did my tests at a compressibility of about 70%, so either will look great. And when both videos look great, I tend to label the one with the highest PSNR as the best.

Quote:
Originally posted by crusty
Good question. I have NO idea how big a QM actually is inside a mpeg4 stream. Anyone got the answer?
All I know is that QM values are 8-bit, so those 64 values would take up 64 bytes. I don't know if they have to be repeated at every QM change, or can be set with a flag with all matrices written out in a header somewhere.
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