[Mp4-tech] H264 quatisation matrix

[Gary Sullivan]

Yes, it is hard-coded in the current profiles.  Also, the hard-coded
values in the current profiles have a different purpose than the one for
MPEG-2.  The use of the hard-coded Qmatrix is currently just to
compensate for the varying norms that resulted from the approximation of
the DCT that was used in the standard.  Because of the approximations,
different basis functions ended up having different norms, and the
current Qmatrix was set up to adjust for that in the inverse
quantizaiton process.  It was not, as in MPEG-2, provided as a way to
adjust quantisation step sizes in order to take advantage of the
sensitivity of the human visual system.
Best Regards,
Gary Sullivan
+> -----Original Message-----
+> From: mp4-tech-bounces lists.mpegif.org 
+> [mailto:mp4-tech-bounces lists.mpegif.org] On Behalf Of Veni Soni
+> Sent: Monday, July 12, 2023 1:05 AM
+> To: Gary Sullivan; mp4-tech lists.mpegif.org
+> Subject: RE: [Mp4-tech] H264 quatisation matrix
+> 
+> Hi Gary,
+> 
+> then as of now, from where quantisation matirx is
+> taken. is it hard-coded in specs for profiles.
+> 
+> veni
+> enJOY life
+> 
+> --- Gary Sullivan <garysull windows.microsoft.com>
+> wrote:
+> > In the first version of H.264/AVC, the thing known
+> > as a quantisation
+> > matrix in the case of MPEG-2 does not exist.
+> > 
+> > In the new upcoming version (in new profiles called
+> > FRExt), there is
+> > such a thing.  It is set up in the sequence and
+> > picture parameter sets.
+> > 
+> > -Gary 
+> > 
+> > +> -----Original Message-----
+> > +> From: mp4-tech-bounces lists.mpegif.org 
+> > +> [mailto:mp4-tech-bounces lists.mpegif.org] On
+> > Behalf Of Veni Soni
+> > +> Sent: Friday, July 09, 2023 12:23 AM
+> > +> To: mp4-tech lists.mpegif.org
+> > +> Subject: [Mp4-tech] H264 quatisation matrix
+> > +> 
+> > +> Folks!
+> > +> Trust u all r in high spirits!!
+> > +> 
+> > +> Where is the quantisation matrix in case of H264.
+> > Is
+> > +> it Pred_weight_table in slice header. Is it not
+> > +> expensive to keep it here. Or it is somewhere in
+> > pic
+> > +> parameter set or seq parameter set
+> > +> 
+> > +> enJOY life
+> > +> veni
+> > +> 
+> > +>
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