[FFmpeg-trac] #10466(undetermined:new): Audio dropouts with Dolby Atmos tracks when seeks or chapter skips are used

[FFmpeg]

#10466: Audio dropouts with Dolby Atmos tracks when seeks or chapter skips are used
-------------------------------------+-------------------------------------
             Reporter:  Vern Dias    |                     Type:  defect
               Status:  new          |                 Priority:  normal
            Component:               |                  Version:
  undetermined                       |  unspecified
             Keywords:  Audio        |               Blocked By:
  dropouts Atmos chapters            |
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |
-------------------------------------+-------------------------------------
 I believe this may be a possible regression as a similar issues was
 reported (and fixed) several years ago.

 It's a little different, because this case only occurs when a chapter seek
 or a skip is used during playback.

 The end result is the same with the following message being logged:

 [ffmpeg] spdif: Unusual frame timing: 21840 => 31612, 40 samples/frame is
 not implemented. Update your FFmpeg version to the newest one from Git. If
 the problem still occurs, it means that your file has a feature which has
 not been implemented.
 [  70.863][w][ffmpeg] spdif: If you want to help, upload a sample of this
 file to https://streams.videolan.org/upload/ and contact the ffmpeg-devel
 mailing list. (ffmpeg-devel at ffmpeg.org)
 [

 Unfortunately the occurrence of the audio skips appears to be random, so
 it would be almost impossible to provide a file.

 ENVIRONMENT:

 mpv 0.35.0-513-gfc3e28f1 Copyright © 2000-2023 mpv/MPlayer/mplayer2
 projects
 built on Sun Jul 09 12:29:05 2023
 libplacebo version: v6.292.0-1-gb959cab-dirty
 FFmpeg version: N-111383-g20b868809
 FFmpeg library versions:
 libavutil       58.14.100
 libavcodec      60.22.100
 libavformat     60.10.100
 libswscale      7.3.100
 libavfilter     9.8.102
 libswresample   4.11.100

 Audio is being bit streamed via HDMI

 DESCRIPTION OF THE ISSUE:

 When playing a BD or UHD disc with a Dolby ATMOS audio track selected and
 using bit-streaming, any seeks or chapter skips will cause intermittent
 audio dropouts. These usually do not occur immediately after the chapter
 skip or seek, but begin several minutes later and with varying frequency.

 Playing the same disk without any seeks or chapter skips does not show
 this issue. I also don't believe that this occurs when bit-streaming is
 disabled.

 The movie used for the attached log files was "Mamma Mia, Here We Go
 Again" (UHD 4K), although I have seen the same issues occur on a number of
 different Dolby ATMOS titles, but only after I have performed a chapter
 skip or timed seek.

 Expected behavior: Normal playback

 Actual behavior: Intermittent audio dropouts when bit-streaming Dolby
 ATMOS tracks.
 I have attached two log files

 Atmos_no_audio_drops_with_no_seeks_chapters.txt

 was created by doing a complete showing of the movie with no user
 intervention.

 Atmos_audio_drops_seeks_chapters.txt

 was created by starting the movie, then performing several chapter skips
 and also several timed seeks just after starting playback. Playback was
 ended after a few occurrences of the audio dropouts.

 One other oddity I see is that the refresh rate which should be 23.976 is
 incorrect starting here in the TrueHD_audio_drop_seeks_chapters.txt log
 file:
 71.253][v][vo/gpu-next/libplacebo] Estimated source FPS: 23.953, display
 FPS: 23.953

 I wonder if this may be the actual cause of the audio dropouts.
-- 
Ticket URL: <https://trac.ffmpeg.org/ticket/10466>
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