[Mp4-tech] Limitation of Max Bin Number For One MB

[Gary Sullivan]

There is a restriction on the total number of bits of data for one MB
(e.g., see item "n" of subclause A.3.1), but I believe there is no
direct limit on bin count per macroblock (except in aggregate as a
per-picture limit).
Regarding the time for decoding on MB - It may be advisable to structure
a decoder such that the entropy decoding process of a slice is operated
on a separate thread or as a first stage prior to the operation of the
remainder of the decoding processes for the macroblocks in the slice,
rather than trying to operate entropy decoding and other steps
sequentially on a per-macroblock basis.
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: Sunday, November 05, 2023 7:17 PM
	To: mp4-tech lists.mpegif.org
	Subject: [Mp4-tech] Limitation of Max Bin Number For One MB
	Dear Experts,
	I have a question regarding the restriction of max bin number
when CABAC is used.
	I can see from the spec, there is a limitation on the max bin
number in a NALU, but I'd like to find out if there is also a limitation
for one MB.
	I searched in the spec and did not find it (there are
limitations for number of times read_bits( 1 ) is called, but it is not
limitations for number of times DecodeBin() is called). Maybe the two
have some relationship which imposed an implied limitation on the number
of times DecodeBin() is called for one MB?
	I have a feeling that if there is no such limitation on the max
bin number for one MB, the time for decoding a MB will be hard to
estimate and this have a bad influence on the real-time pipeline
decoding architecture. In this way, a decoded-buffer of NALU for CABAC
decoding will be needed to balance the influence.
	Thanks in advance for your help.
	Best Regards,
	alan
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