H.263 QM: What are their coefficients?

lcld · 31st May 2005, 07:43

I know, H.263 isn't a matrix-with-fixed-coefficients. At least, that's what I read several times. But how it is possible?

I can't understand how one can experiment with CQM without knowing what H.263 is.

And what about MPEG?

Poutnik · 31st May 2005, 09:48

I do not know much about H263 but it uses different quantization approach,
comparing to MPEG ( no matter if standard MPEG or custom MPEG matrix ).

So CQM have nothing to do with matrices, so one need not to know it.
But fore sure it is useful to know what it is.

Try Google to find some H263 related resources....
I know there are..

iradic · 31st May 2005, 09:59

sorry if OT but what reg value tells xvid which matrix to use?

lcld · 31st May 2005, 10:07

Quote:

Try Google to find some H263 related resources....

reading http://www.uofaweb.ualberta.ca/mccl/...rt-LinWang.pdf...

Quote:

sorry if OT but what reg value tells xvid which matrix to use?

HKEY_CURRENT_USER\SOFTWARE\GNU\XviD\quant_type
HKEY_CURRENT_USER\SOFTWARE\GNU\XviD\qmatrix_inter
HKEY_CURRENT_USER\SOFTWARE\GNU\XviD\qmatrix_intra
???

Poutnik · 31st May 2005, 11:23

IMHO quant type says if h263,MPEG, or MPEG custom is used.
inter/intra keys say which koefs would be used, if Custom MPEG is chosed.
So there is no link to matrix.
When matrix is loaded, data are just copied to these reg items.

lcld · 31st May 2005, 13:28

(The first time I tried to find the answer in xvid's source, I was completely lost.
Now, with that doc, I think I have understood.)

H.263 quantization woulld be a CQM full of 16 with a slightly different algorithm : results of divisions are "truncated", instead of being "rounded".

And MPEG quantization is just a predefined matrix.

Can anyone confirm this ?

Sharktooth · 31st May 2005, 16:52

h263 is a quantization type, not a a quantization matrix.
DivX fusion uses an "optimized" h263 algo, while xvid uses standard h263.

akupenguin · 31st May 2005, 19:29

Quote:

Originally Posted by Sharktooth

DivX fusion uses an "optimized" h263 algo, while xvid uses standard h263.

I was under the impression that DivX's "Rate-distortion optimized H.263 quantization" was just another name for Trellis. After all, they can't change the behaviour of the decoder and still be MPEG4 compliant, so the only choices available are what dct coefficients to encode. And Trellis is precisely the rate-distortion optimal choice of coefficients.

Manao · 31st May 2005, 20:12

akupenguin : It's indeed trellis that is used.

Lcld : I confirm you observation : roughly, h263 is equivalent to a matrix filled with 16s. Roughly only. MPEG is indeed equivalent to MPEG-Custom with a predefined matrix - this matrix is defined in the MPEG-4 norm.

31st May 2005, 07:43	#1 \| Link
lcld Registered User Join Date: Jan 2005 Location: France Posts: 28	H.263 QM: What are their coefficients? I know, H.263 isn't a matrix-with-fixed-coefficients. At least, that's what I read several times. But how it is possible? I can't understand how one can experiment with CQM without knowing what H.263 is. And what about MPEG?

31st May 2005, 09:48	#2 \| Link
Poutnik Useless idea generator Join Date: Apr 2004 Location: Europe, Czech Republic, Brno Posts: 332	I do not know much about H263 but it uses different quantization approach, comparing to MPEG ( no matter if standard MPEG or custom MPEG matrix ). So CQM have nothing to do with matrices, so one need not to know it. But fore sure it is useful to know what it is. Try Google to find some H263 related resources.... I know there are.. __________________ Vista64 Premium SP2 / C2D E4700 2.6GHz/ 6GB RAM/ Intel GMA 3100 / DTV Leadtek DONGLE GOLD USB2 / focused to DVB-T MPEG2 PS capture -> ProjectX -> M2V/MP2 -> MeGUI/AVS -> MP4[AVC/AAC]

31st May 2005, 11:23	#5 \| Link
Poutnik Useless idea generator Join Date: Apr 2004 Location: Europe, Czech Republic, Brno Posts: 332	IMHO quant type says if h263,MPEG, or MPEG custom is used. inter/intra keys say which koefs would be used, if Custom MPEG is chosed. So there is no link to matrix. When matrix is loaded, data are just copied to these reg items. __________________ Vista64 Premium SP2 / C2D E4700 2.6GHz/ 6GB RAM/ Intel GMA 3100 / DTV Leadtek DONGLE GOLD USB2 / focused to DVB-T MPEG2 PS capture -> ProjectX -> M2V/MP2 -> MeGUI/AVS -> MP4[AVC/AAC]

31st May 2005, 13:28	#6 \| Link
lcld Registered User Join Date: Jan 2005 Location: France Posts: 28	(The first time I tried to find the answer in xvid's source, I was completely lost. Now, with that doc, I think I have understood.) H.263 quantization woulld be a CQM full of 16 with a slightly different algorithm : results of divisions are "truncated", instead of being "rounded". And MPEG quantization is just a predefined matrix. Can anyone confirm this ? Last edited by lcld; 1st June 2005 at 17:04.

31st May 2005, 16:52	#7 \| Link
Sharktooth Mr. Sandman Join Date: Sep 2003 Location: Haddonfield, IL Posts: 11,768	h263 is a quantization type, not a a quantization matrix. DivX fusion uses an "optimized" h263 algo, while xvid uses standard h263. __________________ MPEG-4 ASP Custom Matrices: EQM V1(old), EQM AutoGK Sharpmatrix (aka EQM V2), EQM V3HR (updated 01/10/2004), EQM V3LR, EQM V3ULR (updated 04/02/2005), EQM V3UHR (updated 17/12/2004) and EQM V3EHR (updated 05/10/2004) Info about my ASP matrices. MPEG-4 AVC Custom Matrices: EQM AVC-HR Info about my AVC matrices My x264 builds. Mooo!!!

31st May 2005, 09:59	#3 \| Link
iradic Registered User Join Date: Jan 2004 Posts: 332	sorry if OT but what reg value tells xvid which matrix to use?

31st May 2005, 20:12	#9 \| Link
Manao Registered User Join Date: Jan 2002 Location: France Posts: 2,856	akupenguin : It's indeed trellis that is used. Lcld : I confirm you observation : roughly, h263 is equivalent to a matrix filled with 16s. Roughly only. MPEG is indeed equivalent to MPEG-Custom with a predefined matrix - this matrix is defined in the MPEG-4 norm.