[Mp4-tech] Question on pyramidal coding of a GOP in MPEG-4 AVC MainProfile

[daniele renzi (bsoft)]

Dear Hichem,
thanks for your quick response and the document, it was very useful.
Actually I was already thinking about reordering the reference list L0, but what doesn't convince me is the fact that in that case I need to enlarge the size of the reference list L0, in order to be able to get the picture P4 and put it at the head of the list with the reordering operation. 
The problem is that, if I understand correctly the spec at the par. 8.2.4.3.1, the reordering works on the ref pic list, that doesn't contain the picture P4, rather than on the whole DPB (is this correct? Maybe the problem would be solved if the reordering was allowed to be performed on the whole DPB).
Anyway, I think this won't be a big problem, so the solution could be to enlarge the reference picture list L0 size by updating the parameter num_ref_idx_l0_active_minus1, and to perform the reordering operation.
Thank you again
Best regards,
Daniele
  ----- Original Message ----- 
  From: El Mokni, Hichem 
  To: daniele renzi (bsoft) 
  Sent: Friday, March 09, 2024 4:24 PM
  Subject: RE: [Mp4-tech] Question on pyramidal coding of a GOP in MPEG-4 AVC MainProfile
  Dear Daniele,
  I have been working on reference management during the last days, so as an answer to your question, I will vote for your proposition, I mean the reordering operation.
   In fact, even if the needed reference picture P4 does not appear in the reference list (which contains only one reference picture B2), a reordering operation will insert it in the reference list. 
  For the syntax of the reordering operation, it depends whether P4 is a long or short term reference picture, but you will find attached a small good documents which explains at the end the reordering operations, illustrated with a good example.
  I hope I have answered your question.
  Best regards
  Hichem ELMOKNI
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