[Mp4-tech] Does MMCOs has a limitation on the number?

[Gary Sullivan]

There is an implied limit that I believe is somewhere in that
neighborhood due to limitations in the standard that certain actions
cannot be repeated and that certain action cause changes of status that
would prohibit certain other actions from taking place after them and
due to limitations on the total quantity of reference pictures in the
DPB.  But I'm not sure what the exact number is.
Best Regards,
Gary Sullivan
________________________________
	From: mp4-tech-bounces lists.mpegif.org
[mailto:mp4-tech-bounces lists.mpegif.org] On Behalf Of Alan Yan - SH
	Sent: Thursday, October 12, 2023 5:05 AM
	To: mp4-tech lists.mpegif.org
	Subject: [Mp4-tech] Does MMCOs has a limitation on the number?
	Dear Experts,
	I have a question regarding the maximum number of continuous
occurrences of "memory_management_control_operation!=0" in function
dec_ref_pic_marking( ).
	Has h.264 spec defined/implied a limitation on the number of
MMCOs?
	I have checked in the spec and did not see any related
constraints.
	I can see from JM86 code that it uses a link structure which can
support unlimited number of MMCO.
	And I also checked ffmpeg which has defined a "MAX_MMCO_COUNT"
equal to 66, meaning it can support a max number of 66 MMCOs.
	Does the 66 used by ffmpeg have any hidden meaningful insights
or it is just a big-enough number choosing randomly?
	Thanks for your clarification.
	Best Regrads,
	alan
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