[Mp4-tech] How to play with INTRA_DC_VLC_THR to improve codingefficiency?

[Gary Sullivan]

Lefan,
It appears to be in the Simple profile to me.  I'm copying a couple of
key MPEG people so that they will record the report of a MoMuSys
software bug.  If you can describe the bug more precisely to them, it
might help.  E.g., is it an encoding problem or a decoding problem?
(Presumably decoding?)
The obvious way for an encoder to use it to improve coding efficiency is
to count the bits for coding the picture with both VLC types for each
value of QP and pick what gives the best result.  However, that may not
be a practical expectation for many implemenations.
The value of the feature would depend not only on to what extent it
provides coding gain in coding the intra macroblocks, but also how much
of the video is coded as intra -- if the video doesn't contain periodic
intra pictures and if the bit rate is low enough that few macroblocks
are coded as intra within non-intra pictures, then it won't help much.
Best Regards,
Gary Sullivan
+> -----Original Message-----
+> From: mp4-tech-bounces lists.mpegif.org 
+> [mailto:mp4-tech-bounces lists.mpegif.org] On Behalf Of Lefan Zhong
+> Sent: Monday, November 03, 2023 10:35 AM
+> To: mp4-tech lists.mpegif.org
+> Subject: [Mp4-tech] How to play with INTRA_DC_VLC_THR to 
+> improve codingefficiency?
+> 
+> 
+> Hi,
+> 
+> It is very tricky to implement INTRA_DC_VLC_THR, even 
+> Momusys reference code
+> cannot handle it correcly for some corner cases (when first 
+> MB in a packet
+> is skipped).
+> 
+> Does anyone know any reference about the compression 
+> improvement with this
+> complex INTRA_DC_VLC_THR? Or any story about it is in the 
+> standard simple
+> profile?
+> 
+> Thanks,
+> 
+> Lefan
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