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• aacenc_tns : tune and reduce artifacts

  6 décembre 2015, par Rostislav Pehlivanov

  aacenc_tns : tune and reduce artifacts
  There are a couple of major changes here :
  1. Start using TNS coefficient compression.
  
  2. Start using 3 bits per coefficient maximum for short windows.
  
  The bits we save from these 2 changes seem to make a nice impact on the
  
  rest of the file/windows.
  3. Remove special case gain checking for short windows.
  
  4. Modify the coefficient loop to support up to 3 windows.
  
  The additional restrictions on TNS were something that was no in the
  
  specifications and furthermore restricting TNS to only low energy short
  
  windows was done to compensate for bugs elsewhere in the code.
  Overall, the improvements here reduce crackling artifacts heard in very
  
  noisy tracks.
  Signed-off-by : Rostislav Pehlivanov <atomnuker@gmail.com>
  

  • [DH] libavcodec/aacenc_tns.c

• aacenc : mark the "faac"-like coder for removal

  5 décembre 2015, par Rostislav Pehlivanov

  aacenc : mark the "faac"-like coder for removal
  This coder produces a much lower quality audio than the rest, is much
  
  slower and is unstable. Hasn’t been updated for a very long time as
  
  well, hence it is more appropriate to remove it since it also depends on
  
  a big burden of a code (the encode_window_bands_info function which is
  
  just as old, just as unstable and bad and in no way modifiable or
  
  fixable).
  Signed-off-by : Rostislav Pehlivanov <atomnuker@gmail.com>
  

  • [DH] libavcodec/aacenc.c

• FFmpeg/Avconv unable to copy subtitles due to unsupported codec ?

  27 novembre 2015, par its_me

  I’ve got an mp4 file with these streams (avconv -i file.mp4 or ffmpeg -i file.mp4) :

  Stream #0.0(eng): Audio: aac, 48000 Hz, stereo, fltp, 125 kb/s (default)
  
  Stream #0.1(eng): Audio: ac3, 48000 Hz, 5.1, fltp, 384 kb/s
  
  Stream #0.2(eng): Video: h264 (Main), yuv420p, 1280x568, 4027 kb/s, PAR 1:1 DAR 160:71, 23.98 fps, 2997 tbn, 50 tbc (default)
  
  Stream #0.3(eng): Subtitle: c608 / 0x38303663, 0 kb/s
  
  Stream #0.4(und): Subtitle: text / 0x74786574
  
  Stream #0.5: Video: mjpeg, yuvj420p, 667x1000 [PAR 72:72 DAR 667:1000], 90k tbn

  I am trying to strip out the first audio stream from the file like so :

  avconv -i file.mp4 -map 0 -map -0:0 -codec copy file-out.mp4
  
  
  
  # OR #
  
  
  
  ffmpeg -i file.mp4 -map 0 -map -0:0 -codec copy file-out.mp4

  The problem is, I get this error :

  Could not write header for output file #0 (incorrect codec parameters ?): Operation not permitted

  So, I checked if something’s wrong with the mp4 file itself :

  avprobe file.mp4
  
  
  
  # OR #
  
  
  
  ffprobe file.mp4

  And the output says :

  Unsupported codec with id 0 for input stream 3
  
  Unsupported codec with id 94213 for input stream 4

  I have no idea what that means. (Apparently something’s wrong with the subtitles, but I got the video from iTunes.)

  1. What’s wrong ?

  2. Can I simply force avconv/ffmpeg to do what I asked of it (i.e. strip the audio stream & copy the rest as it is) ? If so, how ?

  ---

  Apparently I missed the other errors/warnings in the console output before the final error message, like @aergistal suggested :

  [mp4 @ 0x2645420] Codec for stream 0 does not use global headers but container format requires global headers
  
  [mp4 @ 0x2645420] Codec for stream 1 does not use global headers but container format requires global headers
  
  [mp4 @ 0x2645420] Codec for stream 2 does not use global headers but container format requires global headers
  
  [mp4 @ 0x2645420] Codec for stream 3 does not use global headers but container format requires global headers
  
  [mp4 @ 0x2645420] Codec for stream 4 does not use global headers but container format requires global headers
  
  [mp4 @ 0x2645420] track 2: could not find tag, codec not currently supported in container