[Mp4-tech] MPEG-4 video null P encoding

[Gary Sullivan]

The way to do this is to send a single P slice that contains nothing but
skipped macroblocks.
Because skipped macroblocks are coded using either a run-length or an
adaptive arithmetic coder, this takes very few bits.
You can also use this trick, along with something called reference list
reordering, to resurect a copy of some picture coded in the distant
past.
When arithmetic coding is not in use, yes, it is mb_skip_run that is the
relevant syntax element.
It does not require a whole bit ber macroblock like H.263 did.
-G. 
+> -----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 12:33 AM
+> To: Swapna Matwankar; mp4-tech lists.mpegif.org
+> Subject: Re: [Mp4-tech] MPEG-4 video null P encoding
+> 
+> Hi swapna,
+> 
+> In case of H264, macroblocks are not coded (COD = 1);
+> in terms of field can u what exactly i have to do. Is
+> it mb_skip_run which i have to code for all
+> macroblocks
+> 
+> veni
+> enJOY life
+> 
+> 
+> > 
+> > --- Swapna Matwankar <smatwankar pace.stpp.soft.net>
+> > wrote:
+> > > Hi veni,
+> > > If you are coding H.263 then you can have all the
+> > > macroblocks as not coded (COD = 1). This will
+> > repeat
+> > > the previous frame.
+> > > If you are coding an MPEG4 stream, then you can
+> > put
+> > > a VOP header with VOP coded flag set to 0 in the
+> > > bitstream.
+> > > regards,
+> > > swapna
+> > > 
+> > > ----- Original Message -----
+> > > From: "Veni Soni" <vodprof yahoo.com>
+> > > To: <mp4-tech lists.mpegif.org>
+> > > Sent: Wednesday, July 07, 2023 11:55 AM
+> > > Subject: [Mp4-tech] MPEG-4 video null P encoding
+> > > 
+> > > 
+> > > Hi gr8 video techies,
+> > > 
+> > > just want a little help. Want some code so that it
+> > > can
+> > > generate a dummy P frame with 0 motion and 0 dct..
+> > > that means null.. absolutely.
+> > > 
+> > > veni
+> > > enJOY life
+> > > 
+> > > 
+> > > 
+> > > 
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