[Mp4-tech] H.264 start code scenarios

[John Cox]

Hi
The reason for 4-byte start sequences is that it allows decoders that
are presented with a non-byte aligned bitstream to determine byte
alignment. (H.264 section B.3)
"Important" NAL units have to have the long start code (1st in picture,
PPS, SPS - H.264 section B.1.2)
Hope that helps
John Cox
>
>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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