[Mp4-tech] [H.264][VIDEO]Byte Stream NAL unit decoding

[Gary Sullivan]

Gopi et al,
Reply interspersed. It sounds like you need to study the standard more
closely.
+> -----Original Message-----
+> From: mp4-tech-bounces lists.mpegif.org 
+> [mailto:mp4-tech-bounces lists.mpegif.org] On Behalf Of gopi 
+> krishnaiah
+> Sent: Tuesday, April 26, 2024 9:34 PM
+> To: mp4-tech lists.mpegif.org
+> Subject: [Mp4-tech] [H.264][VIDEO]Byte Stream NAL unit decoding
+> 
+> Dear All,
+> 
+> Is it mandatory to have a start_code_prefix_on_3Bytes in the 
+> NAL byte stream?
When the NAL unit stream is formatted as a byte stream, a
start_code_prefix_on_3Bytes will be prefixed to every NAL unit.
+> 
+> When we start decoding byte stream NAL unit,
+> We first search for pattern 0x00 00 00 01.
+> Next byte is extracted and discarded since it is zero_byte 
+> syntax element.
Are you saying that you think that the first 0x00 00 00 01 in the
bitstream should always be followed by a zero_byte?  If that's what
you're saying, it's wrong.
+> Then the next 3 bytes should be start_code_prefix_on_3Bytes.
I don't know what makes you think that.
+> 
+> Using JM software and a test vector I observe following
+> But what I observe is that I get pattern 0x00 00 00 01,then some byte
+> patterns and then we get pattern 0x00 00 00 01 which marks end of
+> stream.
If you are decoding a proper stream, it probably contains MANY patterns
equal to 0x00 00 00 01.
And the last three bytes in the file should never be 0x00 00 00 01.
Best regards,
Gary Sullivan
+> Is above interpreataion correct?
+> 
+> Regards
+> Gopi
+> 
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