[Mp4-tech] Re: [jvt-experts] gaps_in_frame_num_value_allowed_flag...???

[John Cox]

Dear Deepak
In the case where you have gap_in_frame_nums_allowed=1 then you cannot
tell the difference between a lost reference frame and a frame that was
intentionally dropped - this is true.  However the correct way of
dealing with both cases is exactly the same (in order to preserve to
correct fill of the DPB etc.) so that is OK. In this case if you want to
spot a lost frame you have to notice it being used for reference by a
picture some time later - I do not believe it is suffient to spot it
being included in L0 or L1.
Hope that helps
JC
>Hi Expert,
>
>ya Gary there was error in my first example.Sorry for the mistake.
>Thanks for correcting me.
>
>My next query on this issue is .....based on your reply
>
>>  I think the sequence of frame_num values for the second case would be:
>>
>>  0,1,2,3,4,4,4,5,6,7,0
>>
>>  So for the frames that actually "exist", the frame_num values that you would observe is:
>>
>>  0,1,3,4,4,6,7,0.
>>
>Why the Non -existing frame are considered as "used for reference"
>when those frames are non- existing and why this is affecting the
>"frame_num".
>Why not Non -existing frame are considered as "Not used for reference" .
>
>Actually I am working over "Frame Loss Recovery"....
>For detecting the Frame Loss I am using "frame_num" to detect the
>reference frame and if frame_num is not in order I am considering it
>as unintentional loss of frame as for example...
>(gap =0)
>frame_num :  0,1,3,3,4,5,0 ...
>So there is loss of  frame having frame_num = 2.
>
>I am referring the IEEE paper  Saurav K. Bandyopadhyay and Zhenyu Wu,
>Purvin Pandit, Jill M. Boyce "AN ERROR CONCEALMENT SCHEME FOR ENTIRE
>FRAME LOSSES FOR H.264/AVC" Circuits and Systems, 2006. ISCAS 2006.
>Proceedings. 2006 IEEE International Symposium on Publication Date:
>21-24 May 2006
>
>But if  gap =1.
>How to detect the loss of frames...????
>
>
>
>
>On Fri, Apr 4, 2024 at 9:48 PM, Gary Sullivan
><garysull windows.microsoft.com> wrote:
>>
>>  I think there is an error in your first example (gaps = 0).
>>
>>  Rather than:
>>
>> 0,1,2,3,3,4,5,0
>>  I think the frame_num values will be:
>>  0,1,2,3,3,3,4,0
>>
>>  I think the sequence of frame_num values for the second case would be:
>>
>>  0,1,2,3,4,4,4,5,6,7,0
>>
>>  So for the frames that actually "exist", the frame_num values that you would observe is:
>>
>>  0,1,3,4,4,6,7,0.
>>
>>  Best Regards,
>>
>>  Gary Sullivan
>>
>>  +> -----Original Message-----
>>  +> From: jvt-experts-bounces lists.rwth-aachen.de
>>  +> [mailto:jvt-experts-bounces lists.rwth-aachen.de] On Behalf
>>  +> Of Deepak Singh
>>  +> Sent: Friday, April 04, 2024 4:17 AM
>>  +> To: jvt-experts lists.rwth-aachen.de; mp4-tech lists.mpegif.org
>>  +> Subject: [jvt-experts] gaps_in_frame_num_value_allowed_flag...???
>>  +>
>>  +> Dear Experts,
>>
>>
>> +>
>>  +>   I have query related to
>>  +> gaps_in_frame_num_value_allowed_flag and frame_num.
>>  +>
>>  +>   As per my understanding of standard when
>>  +>   gaps_in_frame_num_value_allowed_flag is 0 then frame_num will be in
>>  +>  non decreasing order and increases till next IDR frame.
>>  +>
>>  +> The value of frame_num  increase with plus 1 with respect to previous
>>  +>  reference frame.
>>  +>
>>  +>   Let me put an example for it.
>>  +>
>>  +>   Lets assume B- frame is not used for reference.
>>  +>   In h.264 coded bitstream the frames are : (frame_num as per my
>>  +>   understanding it will be)
>>  +>   Note: gaps_in_frame_num_value_allowed_flag = 0
>>  +>
>>  +>   Coded Frame  :  IDR -> P-> P-> B->B-> P-> P->IDR->....
>>  +>   Frame_num    :  0         1    2     3    3    4    5     0
>>  +>
>>  +>   My question is for the same sequence if
>>  +>   gaps_in_frame_num_value_allowed_flag = 1 and non- existing frame
>>  +>   exists as
>>  +>
>>  +>   Note: gaps_in_frame_num_value_allowed_flag = 1, NE = Non
>>  +> Existing Frame.
>>  +>   Coded Frame : IDR -> P-> NE->P-> B->B->NE->NE-> P-> P->IDR->....
>>  +>   Frame_num   :  0       1     ?      ?     ?    ? ?     ?
>>  +>     ?     ?     0
>>  +>
>>  +>   How the frame_num value will behave for the above situation???
>>  +>
>>  +>
>>  +>   --
>>  +>   Regards,
>>  +>   Deepak Singh
>>  +>
>>  +>
>>  +>
>>  +>  --
>>  +>  Regards,
>>  +>  Deepak Singh
>>  +>
>>  +>  Visit my blog for cool stuff...
>>  +> http://www.thinknaturally.blogspot.com/
>>  +>
>>  +>
>>  +>
>>  +> *************************************************************
>>  +> *********************************
>>  +>  "If u really aspire for the FIRST place ,then there is no
>>  +> second place
>>  +>  in this world"
>>  +>
>>  +> *************************************************************
>>  +> ***********************************
>>  +>  My phone:09341097500 Just DIL SE........
>>  +>   With caresss.
>>  +>
>>  +>
>>  +>
>>  +> --
>>  +> Regards,
>>  +> Deepak Singh
>>  +>
>>  +> Visit my blog for cool stuff...
>>  +> http://www.thinknaturally.blogspot.com/
>>  +>
>>  +>
>>  +> *************************************************************
>>  +> *********************************
>>  +> "If u really aspire for the FIRST place ,then there is no
>>  +> second place
>>  +> in this world"
>>  +> *************************************************************
>>  +> ***********************************
>>  +> My phone:09341097500 Just DIL SE........
>>  +>  With caresss.
>>  +> _______________________________________________
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>>