[Mp4-tech] H.264 frame rate

[Gary Sullivan]

Please define the term frame rate.  Are you under the impression that the number of decoded pictures per second needs to be a constant?  If so, that is an incorrect impression in some use cases.
If there is no frame rate expressed in the video elementary stream syntax, there may be such an animal defined in a system-level or application-level specification.
If there isn't, then it is possible that the video bitstream does not have a frame rate (depending on your definition of what a frame rate is).
However, there will be a constraint on how close together in time the decoder can be required to decode each pair of consecutive pictures in the bitstream in decoding order.  Similarly there will be a constraint on how close together in time the decoder can be required to output each pair of consecutive pictures in the bitstream in output order.  Those constraints are specified by the level constraints in Annex A.
Best Regards,
Gary Sullivan
________________________________
	From: mp4-tech-bounces lists.mpegif.org [mailto:mp4-tech-bounces lists.mpegif.org] On Behalf Of ChenJianjun
	Sent: Tuesday, August 14, 2023 5:41 AM
	To: mp4-tech lists.mpegif.org
	Subject: [Mp4-tech] H.264 frame rate
	Dear experts:
	How to calculate the H.264 frame rate? 
	I noted that VUI parameter(SPEC E.1) and Picture timing SEI message semantics(SPEC D.2.2) may have such information.But they are optional,then how to get the frame rate information if there's no such information?
	Thanks!
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