[FFmpeg-trac] #11630(avcodec:new): Regression: hevcdec with videotoolbox hwaccel aborts on broken frames after commit 79afc45c03abfb7f1d9dc2cc758ec162bfade1a0

[FFmpeg]

#11630: Regression: hevcdec with videotoolbox hwaccel aborts on broken frames after
commit 79afc45c03abfb7f1d9dc2cc758ec162bfade1a0
-------------------------------------+-------------------------------------
             Reporter:  gnattu       |                     Type:  defect
               Status:  new          |                 Priority:  normal
            Component:  avcodec      |                  Version:  git-
             Keywords:               |  master
  videotoolbox hevc                  |               Blocked By:
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |
-------------------------------------+-------------------------------------
 Summary of the bug:

 Since commit `79afc45c03abfb7f1d9dc2cc758ec162bfade1a0` (lavc/hevcdec: use
 a ContainerFifo to hold frames scheduled for output), the behavior of the
 HEVC decoder (`hevcdec`) with videotoolbox hardware acceleration has
 changed. When decoding input files that contain broken frames, the decoder
 now aborts early instead of continuing to decode subsequent good frames,
 as it did before.

 This is verified by bisecting from 7.0.2 to 7.1.1:

 {{{
 79afc45c03abfb7f1d9dc2cc758ec162bfade1a0 is the first bad commit
 commit 79afc45c03abfb7f1d9dc2cc758ec162bfade1a0
 Author: Anton Khirnov <anton at khirnov.net>
 Date:   Thu Jun 20 21:01:49 2024 +0200

     lavc/hevcdec: use a ContainerFifo to hold frames scheduled for output

     Instead of a single AVFrame.

     Will be useful in future commits, where we will want to produce
 multiple
     output frames for a single coded frame.

  libavcodec/Makefile       |  2 +-
  libavcodec/hevc/hevcdec.c | 31 +++++++++++++++++++++----------
  libavcodec/hevc/hevcdec.h |  4 ++--
  libavcodec/hevc/refs.c    | 12 ++++--------
  4 files changed, 28 insertions(+), 21 deletions(-)
 }}}

 How to reproduce:
 1. Download this sample, which contains broken frames at the beginning:

 https://drive.usercontent.google.com/download?id=1z5dRzJ1PMSTphUqXa379Ourm1OdARIO_&export=download&authuser=0

 2. Run the following command:

 {{{
 ./ffmpeg -hide_banner -hwaccel videotoolbox -hwaccel_output_format
 videotoolbox_vld -i './LG Cymatic Jazz 4K Demo.ts' -vcodec
 h264_videotoolbox -an -sn -dn test.mp4
 }}}

 You should observe the bug, where decoding aborts after encountering
 broken frames instead of continuing:

 {{{
 [hevc @ 0x142e1e860] No frame decoded?
 [vist#0:0/hevc @ 0x144004b90] [dec:hevc @ 0x142e17820] Error submitting
 packet to decoder: Generic error in an external library
 [vist#0:0/hevc @ 0x144004b90] [dec:hevc @ 0x142e17820] Error submitting
 packet to decoder: Unknown error occurred
 [vist#0:0/hevc @ 0x144004b90] [dec:hevc @ 0x142e17820] A decoder returned
 an unexpected error code. This is a bug, please report it.
 [vist#0:0/hevc @ 0x144004b90] [dec:hevc @ 0x142e17820] Error processing
 packet in decoder: Internal bug, should not have happened
 [vist#0:0/hevc @ 0x144004b90] [dec:hevc @ 0x142e17820] Task finished with
 error code: -558323010 (Internal bug, should not have happened)
 [vist#0:0/hevc @ 0x144004b90] [dec:hevc @ 0x142e17820] Terminating thread
 with return code -558323010 (Internal bug, should not have happened)
 }}}

 In 7.0.2, it will continue decoding past the broken frames, despite the
 log is also flooded with decode errors:

 {{{
 [hevc @ 0x150e1efa0] Could not find ref with POC 38
 [hevc @ 0x150e175b0] vt decoder cb: output image buffer is null: -17694
 [hevc @ 0x150e1efa0] hardware accelerator failed to decode picture
 [vist#0:0/hevc @ 0x150e08d30] [dec:hevc @ 0x150e16020] Error submitting
 packet to decoder: Unknown error occurred
     Last message repeated 7 times
 }}}


 A temporary workaround is to change line 127 of `videotoolbox.c` to not
 return `AVERROR_EXTERNAL` if no frame was decoded, but to return 0 after
 unreffing the frame. This allows decoding to continue with invalid frame
 warning:

 {{{
 [hevc @ 0x11a604f40] An invalid frame was output by a decoder. This is a
 bug, please report it.
 }}}

 But this is probably not the best way to restore the old behavior, and
 therefore I created this ticket.
-- 
Ticket URL: <https://trac.ffmpeg.org/ticket/11630>
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