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View Full Version : What are MPEG-2 h.263 and h.264 quantitisers

Esurnir
22nd January 2009, 04:50
I would like to know a quant matrix if I did my homework right are "values" which are to be multiplied to the residual before performing iDCT / theh.264equivalentofit.

Now when I get a qp of let's say 8 what are the values of the quant matrix ?

My current guess is :
for mpeg-2 : 8 time the matrix (http://img207.imageshack.us/img207/374/quantqf8.jpg) of the movie.
for h.263 matrices : a matrix full of 64.
for h.264 movies : a matrix full of 8.

Did I got it right or there is a weird scaling rule somewhere ?
Dark Shikari
22nd January 2009, 04:53
The quantization matrix has nothing to do with the quantizer.

The quantization matrix are values that are used to scale the quantization multiplication factors (quant_mf in x264) and dequantization accordingly. Those depend on the quantizer of course, but the effect is the same regardless of quantizer.
Esurnir
22nd January 2009, 05:00
The quantization matrix has nothing to do with the quantizer.

The quantization matrix are values that are used to scale the quantization multiplication factors (quant_mf in x264) and dequantization accordingly. Those depend on the quantizer of course, but the effect is the same regardless of quantizer.

I think I was a bit naive to think reading the jpeg wikipedia article was going to give me enough information to understand that process... Is there any faq about the quantization process in h.264 or mpeg-2 or I should get some tylenol and dwelve in the h.264 itu-t standard ?
Esurnir
25th January 2009, 22:13
Actually the source is quite clear. Thanks