[Mp4-tech] Regarding Gaps in Frame number

[Ye-Kui.Wang nokia.com]

If gaps_in_frame_num_value_allowed_flag is equal to 0, then a gap in
frame_num could be used to detect a reference picture loss. If the flag
is equal to 1, then a gap in frame_num does not necessarily mean there
is reference picture loss, it may also because discarding of temporal
scalable enhancement layers containing reference pictures. See the three
types of sub-sequence related SEI messages in Annex D for more detail. 
BR, YK
>-----Original Message-----
>From: mp4-tech-bounces lists.mpegif.org 
>[mailto:mp4-tech-bounces lists.mpegif.org] On Behalf Of ext 
>Wesley De Neve
>Sent: Tuesday, August 01, 2023 4:14 PM
>To: Sri; mp4-tech lists.mpegif.org
>Subject: Re: [Mp4-tech] Regarding Gaps in Frame number
>
>Dear Srihari,
>
>A gap in the value of the frame_num syntax element (in the 
>slice header syntax structure of H.264/AVC) indicates that a 
>reference picture is missing (frame_num acts as a counter that 
>is incremented *after* the decoding of a reference picture, 
>but not after the decoding of a non-reference picture). 
>This functionality can for instance be used for the purpose of 
>error conceilment.
>
>A search in the archives of this mailing list (maybe using 
>Google) might be useful as the semantics of frame_num has 
>already been discussed a few times in the past.
>
>Best regards,
>Wesley De Neve
>
>Sri wrote:
>> Dear All,
>>
>> Can anyone tell me the signficance of Gaps in frame number in H.264.
>> why it is used.
>>
>> Regards,
>> Srihari
>>
>> 
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