[FFmpeg-trac] #11055(avcodec:reopened): OGOP (Open GOP) in certain conditions may cause missing frames of decoding

[FFmpeg]

#11055: OGOP (Open GOP) in certain conditions may cause missing frames of decoding
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             Reporter:  markfilipak  |                    Owner:  (none)
                 Type:  defect       |                   Status:  reopened
             Priority:  normal       |                Component:  avcodec
              Version:  git-master   |               Resolution:
             Keywords:  everything   |               Blocked By:
  OGOP                               |
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |
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Comment (by pdr0):

 Replying to [comment:185 Balling]:
 > Pdr0, is not there is a recovery point in the start? Elecard 2023 says
 so.
 >
 > "However, according to the spec (08/21; annex D.2.8), this recovery
 point SEI may have a flag exact_match=1, which means "if you start
 decoding here, you get exactly the same frames, as if you started decoding
 at the previous IDR."


 Yes, but it's still not a valid sequence as per the ITU h264 specs

 7.4.1.2.2
 "A bitstream conforming to this Recommendation | International Standard
 consists of one or more coded video sequences. The first access unit of
 each coded video sequence is an IDR access unit."

 To clarify that the above applies to decoding order, not display order:
 3.64
 "The first picture of each coded video sequence in decoding order is an
 IDR picture."


 As for the other issues, eg. the 1st frame in coded order specifies a
 frame_num of 227 and pic_order_count_lsb as 362 in this 99 frame sample...
 another issue is the values are supposed to increase in decoding order
 according to the specs, but there are examples where they  decrease. This
 might be contributing to some of the problems observed with ffmpeg
 timestamps
-- 
Ticket URL: <https://trac.ffmpeg.org/ticket/11055#comment:188>
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