[Mp4-tech] question on mpeg4 part 2 dquant

[Gary Sullivan]

Your interpretation is correct.  I think I recently mentioned a weakness of the MPEG-4p2 dquant design on email on this reflector recently -- this was what I was alluding to.  It can make rate control a little tricky.  Basically you must find a way to decide which is more important to you -- using 4mv or using dquant.  That's a kind of strange decision to need to make, but that's the way it works.  It's probably not a major problem, but it's a little quirk you need to find a way around in your design.
That's a little design bug that came into MPEG-4p2 from H.263v1.  I recall that we put some kind of tweak into H.263+ to fix it, but somehow the MPEG-4p2 design went ahead with the old design without including the fix.
Best Regards,
-Gary Sullivan
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	From: mp4-tech-bounces lists.mpegif.org [mailto:mp4-tech-bounces lists.mpegif.org] On Behalf Of ???
	Sent: Monday, March 28, 2024 6:40 PM
	To: mp4-tech lists.mpegif.org
	Subject: [Mp4-tech] question on mpeg4 part 2 dquant
	dear expert:
	    I find only When macro type is inter+q and intra+q can write dquant value in mpeg4 part 2 standard,so when macro type is inter4v can't write dquant value because have not inter4v+q macro mode in ISO/IEC 14496-2,that is to say when macro have four motion vector ,it can not change quant value in macro level. So I was question how can implement macro level rate control when a frame have a lot inter4v macro ? Have I misunderstood 14496-2 standard? I was reference ISO/IEC 14496-2 Second edition 2001-12-01.And I find xvid write dquant and decode dquant as above. Can somebody of mpeg4 part 2 expert answer my question?
	thanks so much
	xiongshu deng
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