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• How to disable non-1st Audio Streams/Tracks in FFmpeg for mp4 files

  16 décembre 2016, par Dipesh

  My end goal is to create a single FFmpeg command that will convert my h264.DTS.mkv files to a format that is compatible with my AppleTV, whilst preserving the original quality.

  I’m almost there, however I have not been able to figure out how to disable streams/tracks.

  So far I have got :

  ffmpeg -i FILE \
  
   -y -strict experimental \
  
   -map 0:0 -map 0:1 -map 0:1 -map 0:1 -map 0:2 \
  
   -c:0 copy -c:1 aac -ac:a 2 -c:2 ac3 -ac:a 6 -c:3 copy -c:4 mov_text \
  
   OUTPUT

  This produces an output file that looks like :

  1. H264 video track (enabled) [copied from original]
  2. AAC 2 channel audio track (enabled)
  3. AC3 6 channel audio track (enabled)
  4. DTS 6 channel audio track (enabled) [copied from original]
  5. subtitle track (enabled)

  The problem is I need it to look like :

  1. 1 H264 video track (copied from original) (enabled)
  2. 1 AAC 2 channel audio track (enabled)
  3. 1 AC3 6 channel audio track (disabled)
  4. 1 DTS 6 channel audio track (copied from original) (disabled)
  5. 1 subtitle track (enabled)

  Hence I need to know how I can disable the non-1st Audio Streams/Tracks.

  From what I have read, this is part of the track header atom at the location "tkhd.flags". But I have not been able to figure out how to set this via command line arguments.

  Any help would be greatly appreciated.

• Use FFMPEG to export audios with gaps filled

  17 octobre 2018, par jcea

  I have a MKV file with gaps in the audio. That is, there are gaps in the MKV audio track timestamps. According to "ffmpeg", the AC3 audio length is 802 seconds, but when exporting the audio to WAV, the resulting file length is 801’53 seconds. That is, the "exported" audio is shorter.

  Triaging the issue with

  ffmpeg -i INPUT.mkv -af ashowinfo -map 0:2 -y -frames:a XXXX -f alaw /dev/null

  I can confirm that the length difference is consistent with gaps in the timestamps of the original audio frames. There are a handful of missing audio frames. I guess those are replaced by silence in the player.

  The command I use to export the audio is :

  ffmpeg -i INPUT.mkv -map 0:1 -ac 2 OUTPUT.wav

  My question is : How can I instruct FFMPEG to preserve the gaps in the original audio, zero (silence) filled ?. The WAV file duration should be the same than the original AC3 audio.

  Given my current workflow, I would rather prefer to not keep the original timestamps in the output file but generate a WAV with (tiny) silences instead. I could consider keeping timestamps if there is no other choice, but this could be quite a pain in my workflow.

  Advice ? Help ?

  Thanks a lot in advance !

• iOS Recorded Video Playback on Android

  1er mars 2015, par Nirav

  I am trying to record video from iPhone device using UIImagePickerController and able to store it in MP4 format. The same video is uploaded on the Amazon S3 cloud.

  When I try to play the same video on Android devices, it fails to play with an error, cannot play.

  I searched forums/google and found that ffmpeg should be used to compress the video before uploading. I want to do the compression on the phone itself rather than on the server. Which is the best way to achieve this ?

  Regards,

  Nirav