[Mp4-tech] H.264 start code scenarios

[Gary Sullivan]

This depends on what you call the start code.  In the bitstream format specified in Annex A, at the beginning of the byte stram and between each pair of byte stream NAL units, the following pattern is present: N bytes equal to 0 followed by a byte equal to 0x01.  For the first NAL unit of each access unit, the constraint is N >= 3.  For other NAL units, the constraint is N >= 2.
Best Regards,
Gary Sullivan
________________________________
	From: mp4-tech-bounces lists.mpegif.org [mailto:mp4-tech-bounces lists.mpegif.org] On Behalf Of shanmugavel.balasubramanian wipro.com
	Sent: Tuesday, July 03, 2023 4:08 AM
	To: mp4-tech lists.mpegif.org; mp4-tech lists.mpegif.org
	Subject: [Mp4-tech] H.264 start code scenarios
	Hi All,
	I have seen some of the H.264 encoded streams having a start code of length 3 and some with 4.
	1. why is it that " number of preceding zeros is two in some cases and 3 in some cases". 
	2. does the number difference for start code length have any significance. Can the length of start code change from NAL to NAL in a sequence. 
	Best Regards,
	Velu
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