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• avformat/isom : lpcm in mov default to big endian

  1er novembre 2013, par Mark Himsley

  avformat/isom : lpcm in mov default to big endian
  It is my understanding that "Unless otherwise stated, all data in a
  
  QuickTime movie is stored in big-endian byte ordering" [1] in MOV files.
  I have a couple of thousand files, which technically are invalid because
  
  their sound sample description element 4CC is ’lpcm’ but its version is
  
  0 - and "Version 0 supports only uncompressed audio in raw (’raw ’) or
  
  twos-complement (’twos’) format" [2]
  Because isom.c only contains a mapping for 4CC ’lpcm’ to
  
  AV_CODEC_ID_PCM_S16LE, these files have their audio decoded as LE when
  
  it is actually BE.
  This commit adds AV_CODEC_ID_PCM_S16BE as the first match for 4CC ’lpcm’.
  [1]
  
  https://developer.apple.com/library/mac/documentation/quicktime/QTFF/qtff.pdf
  
  page 21
  
  [2]
  
  https://developer.apple.com/library/mac/documentation/quicktime/QTFF/qtff.pdf
  
  page 178
  Reviewed-by : Yusuke Nakamura <muken.the.vfrmaniac@gmail.com>
  
  Signed-off-by : Michael Niedermayer <michaelni@gmx.at>
  

  • [DH] libavformat/isom.c

• I would like to batch-trim mp4 videos in a folder with command line (ffmpeg ?), however the sound is delayed

  28 janvier 2023, par pdeli

  I found the following command line to batch-trim videos in a folder, however it delays the sound of all the videos by a few seconds (sound comes after the video) :

  


  for file in /path/to/folder/*.mp4; do ffmpeg -i "$file" -ss 00:00:08 -c copy -avoid_negative_ts 1 "${file%.*}_trimmed.mp4"; done

  


  These are the alternatives I found, however none of them solve the problem :

  


  for file in /path/to/folder/*.mp4; do ffmpeg -i "$file" -itsoffset -0.5 -ss 8 -c:v copy -c:a copy "${file%.*}_trimmed.mp4"; done

  


  for file in /path/to/folder/*.mp4; do ffmpeg -i "$file" -ss 8 -async 1 -c:v copy -c:a copy "${file%.*}_trimmed.mp4"; done

  


  for file in /path/to/folder/*.mp4; do ffmpeg -i "$file" -ss 8 -map 0:v -map 0:a -c:v copy -c:a copy "${file%.*}_trimmed.mp4"; done

  


  I have a hard time finding by how much time the sound is delayed.

  


  My questions :

  


  

  • what would be the command line to batch-trim the beginning of all the videos in a folder with the sound properly "aligned" to the video ?

  


  • in other words, can't the sound be by default trimmed by as much as the video in the first place ? If yes, how ?

  


  


  ---

  


  System used :

  


  

  • macOS Ventura (13.1, Intel)

  


  • Shell and version : zsh 5.8.1 (x86_64-apple-darwin22.0)

  


  • ffmpeg version 5.0 built with Apple clang version 13.0.0 (clang-1300.0.29.30)

  


  


• Podcast : Transform images and audio in a Podcast [on hold]

  27 juin 2013, par Henry Mazza

  Garage Band and others can make podcasts with embedded images to make a slideshow. Is there a way to do this in the command line with tools like ffmpeg ?