[Mp4-tech] [H.264] [Q] SEI and AU.

[Gary Sullivan]

Chulsoo Lee et al,
Please see comments below.
Best Regards,
Gary Sullivan
+> -----Original Message-----
+> From: mp4-tech-bounces lists.mpegif.org 
+> [mailto:mp4-tech-bounces lists.mpegif.org] On Behalf Of ???
+> Sent: Saturday, August 27, 2023 11:59 PM
+> To: mp4-tech lists.mpegif.org
+> Subject: [Mp4-tech] [H.264] [Q] SEI and AU.
+> 
+> 
+> Dear Experts,
+> 
+> I have a question about Picture timing SEI message syntax.
+> What is the linkage information that ties timestamp to coded slice
+> information?
The picture timing SEI message is found in the same "access unit" as the slices to which it applies.
+> Does every coded slice follows the corresponding SEI message?
When picture timing SEI is in use there would be one picture timing SEI message and possibly multiple slices per decoded picture.
+> If there is additional information such as MPEG-4 SL layer 
+> or MPEG2 TS, 
+> is the timing SEI message useless? I wonder if MPEG2 TS does 
+> not deliver
+> the 'contents time informations', how to deliver them and 
+> reconstruct them.
Information provided at the system level should probably be considered preferable to information provided in the video elementary stream.
In some cases (e.g., MPEG-2) there might be timestamps available in the systems-lvel information that is incomplete (e.g., timestamps on some but not all pictures).  In such cases I believe the video elementary stream data may be useful to infer the missing data.
Note also that in some types of use (e.g., when fixed_frame_rate_flag is equal to 1) it should be very easy to construct the output timing.
+> I am thirsty of the information.
+> 
+> Thanks in advance.
+> 
+> regards,
+> Chulsoo Lee.
+> 
+>  
+> 
+> 
+> 
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