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• How to merge two audio files while retaining correct timings with ffmpeg

  31 août 2017, par andy

  Disclaimer : I don’t understand ffmpeg and mostly just copy commands

  I have two webm video files. Their duration is off by about a second.

  I converted these to mp4 and everything was fine :

  ffmpeg -acodec libopus -i 1.webm -r 10 -cpu-used 5 -c:v libx264 -crf 20 -c:a aac -strict experimental -loglevel error 1.mp4

  I then extracted the audio from each video and everything was fine. By fine, I mean, when I playback the audio files by themselves they match the timings on the original video. I used this command to extract the audio :

  fmpeg -i 1.mp4 -map 0:a -vn -acodec copy 1audio.m4a

  I now have two audio tracks and I want to combine them into one, I want to "overlay" them, AND I want to keep the timings the same as they were.

  BUT, whenever I try and combine the audio the timings are off. The "seconds" don’t match the original single audio files.

  I have tried these commands to merge the audio :

  ffmpeg -i 1audio.m4a -i 2audio.m4a -filter_complex "[0:a][1:a]amerge=inputs=2[a]" -map [a] -c:a libfdk_aac mergedaudio.m4a

  ffmpeg -i 2audio.m4a -i 1audio.m4a -filter_complex amix=inputs=2:duration=first mergedaudio.m4a

  ffmpeg -i 1audio.m4a -i 2audio.m4a -filter_complex amerge -ac 2 -c:a libfdk_aac -vbr 4 mergedaudio.m4a

  All the above command have resulted in a merged audio file... but the timings are off.

  What am I doing wrong ?

• ffmpeg export video from png sequence is not correct

  24 août 2017, par chris young

  I have a PNG sequence with transparent background.

  When I use Adobe Media encoder to export to an MP4 file, the result is correct.

  But when I use FFmpeg to export the MP4 file, this result is very strange.

  This is the command I used :

  ffmpeg -i test/frame_%04d.png -pix_fmt yuv444p -c:v libx264 -y ffmpeg_test.mp4

  Media Encoder : http://test.rto.im/ffmpeg/media_encoder_test.mp4

  FFMPEG : http://test.rto.im/ffmpeg/ffmpeg_test.mp4

  All images file : test.rto.im/ffmpeg/test.zip

  test.rto.im/ffmpeg/test/frame_0001.png

  test.rto.im/ffmpeg/test/frame_0002.png

  test.rto.im/ffmpeg/test/frame_0003.png
  ....

• How to load correct libavcodec.so shared library version ? (53)

  6 août 2017, par user2212461

  I am using libavcodec and libavformat in my project but when I execute a binary which was built on another machine, I get the following error :

  error while loading shared libraries: libavcodec.so.53: cannot open shared object file: No such file or directory

  I installed ffmpeg with libav and trying the following commands :

  sudo apt-get install ffmpeg libavcodec-dev libavformat-dev
  
  sudo apt-get install ffmpeg libavcodec-extra-53
  
  sudo apt-get install libav-tools

  The error doesnt show up when I build the binary on the same machine, but it would be much faster to compile on a second machine.

  UDPATE : I also ran sudo apt-get install update and sudo apt-get install pkg-config without any change in the output. (OS = 12.04)