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• lavc : add a codec flag for propagating opaque from frames to packets

  12 juillet 2022, par Anton Khirnov

  lavc : add a codec flag for propagating opaque from frames to packets
  This is intended to be a more convenient replacement for
  
  reordered_opaque.
  Add support for it in the two encoders that offer
  
  AV_CODEC_CAP_ENCODER_REORDERED_OPAQUE : libx264 and libx265. Other
  
  encoders will be supported in future commits.
  

  • [DH] doc/APIchanges
  • [DH] libavcodec/avcodec.h
  • [DH] libavcodec/encode.c
  • [DH] libavcodec/libx264.c
  • [DH] libavcodec/libx265.c
  • [DH] libavcodec/options_table.h
  • [DH] libavcodec/version.h

• Extracting a bit broken AC3 audio from a video file

  3 janvier 2023, par WYSIWYG

  I Googled for about 2 hours for this problem and I can't seem to find the answer anywhere.

  


  So I have a 1080p video file which has about 2 seconds within it that's broken (at 3 minutes and 53 seconds). I found a way to extract the non-broken parts of it, also I got a replacement for the broken frames from another version of the same video (in 720p), upscaled them to 1080p and replaced them in the 1080p file (reencoding the whole file in the process). Here comes the problematic part - at the same time (3 min 53 sec), the audio is also broken and it's in Dolby Digital 5.1 AC3 format. When I try to extract the audio track from the original 1080p file and place the result in the new fixed version, which contains the upscaled video frames, the audio obviously is cut at the problematic 2 seconds and it desyncs (starts to play earlier) for the rest of the file.

  


  What I want to do and I'm unable to understand how to do it is to extract the AC3 stream in such a way that the 2 broken seconds are filled with silence and the total length of the audio stay the same as the original, so it won't desync. Is this possible and if it is, what is the correct FFMPEG command for it ?

  


  Thank you in advance.

  


  I've tried :

  


  ffmpeg -i broken.mkv -c:a copy audio.ac3

  


  which presented an output AC3 file, which is missing the 2 seconds from 03:53 to 03:55

  


  so when I combine the resulting AC3 file with the repaired video, by using :

  


  ffmpeg -i fixed.mkv -i audio.ac3 -c copy fixed-with-audio.mkv

  


  it is desynced, so at video time 03:53 I hear the audio that should play at 03:55

  


• avcodec/vc1dec : Split VC-1 decoders from msmpeg4

  30 octobre 2022, par Andreas Rheinhardt

  avcodec/vc1dec : Split VC-1 decoders from msmpeg4
  The only msmpeg4 code that is ever executed by the VC-1 based
  
  decoders is ff_msmpeg4_decode_init() and what is directly
  
  reachable from it. This is :
  
  a) A call to av_image_check_size(), then ff_h263_decode_init(),
  
  b) followed by setting [yc]_dc_scale_table and initializing
  
  scantable/permutations.
  
  c) Afterwards, some static tables are initialized.
  
  d) Finally, slice_height is set.
  The replacement for ff_msmpeg4_decode_init() performs a)
  
  just like now ; it also sets [yc]_dc_scale_table,
  
  but it only initializes inter_scantable and intra_scantable
  
  and not permutated_intra_[hv]_scantable : The latter are only
  
  used inside decode_mb callbacks which are only called
  
  in ff_h263_decode_frame() which is unused for VC-1.*
  The static tables initialized in c) are not used at all by
  
  VC-1 (the ones that are used have been factored out in
  
  previous commits) ; this avoids touching 327KiB of .bss.
  slice_height is also not used by the VC-1 decoder (setting
  
  it in ff_msmpeg4_decode_init() is probably redundant after
  
  b34397b4cd780b5692548e7d021ec884c7217dba).
  * : It follows from this that the VC-1 decoder is not really
  
  based upon the H.263 decoder either ; changing this will
  
  be done in a future commit.
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
  

  • [DH] configure
  • [DH] libavcodec/msmpeg4.c
  • [DH] libavcodec/msmpeg4dec.c
  • [DH] libavcodec/vc1dec.c