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• Batch merge audio files by specific timestamp without reencoding

  8 mai, par Saccarab

  I want to batch merge mp3 audio files where every single file has a specific start time. So below is the fluent-ffmpeg spawn I use right now to merge 3 files with each starting at respectively 200, 7400 and 10600.

  



  ffmpeg -i firstFile.mp3 -i secondFile.mp3 -i thirdFile.mp3 -filter_complex 
[0]adelay=200[a0];[1]adelay=7400[a1];[2]adelay=10600[a2];[a0][a1] 
[a2]amix=inputs=3:dropout_transition=1000,volume=3 -f mp3 pipe:1


  



  This works pretty good, except for longer files re-encoding makes the process take real long. So I wanted to do the same thing using concat demuxer. Since I already know how long each audio file is, I've put in silent audio files between them to create a delay until next audio file so it actually starts on the time position it is supposed to.

  



  #concatfile.txt

file silence.mp3
outpoint 200
file firstFile.mp3
file silence.mp3
outpoint 1500
file secondFile.mp3
file silence.mp3
outpoint 2000
file thirdFile.mp3

ffmpeg -f concat -safe 0 -i concatfile.txt -c copy output.mp3


  



  This solution also works okay when merging few files but when I merge higher count of files like 30 or 40 result file will have a slowly increasing synchronization problem where audio files actually start later than the start timestamps they are supposed to have.

  



  Looks like an issue similar to this post

  



  I'm open for any suggestion on solving the issue.

  


• Audio conversion and filter application using ffmpeg with 1 command

  1er juillet 2019, par user2773013

  I have an mp3 file I need to convert to wav, and apply loudnorm filter afterwards. So far i’ve been doing it with 2 commands.

  ffmpeg -i input.mp3 output.wav

  and

  ffmpeg -y -nostdin -i output.wav -filter_complex "[0:0]FILTER PARAMETER" -map_metadata 0 -map_metadata:s:a:0 0:s:a:0 -map_chapters 0 -map [norm0] -c:a pcm_s16le -ar 1500 -c:s copy out2.wav   

  Is there anyway to use 1 command instead of 2 ? I tried converting straight from mp3 to out2.wav by changing output.wav to input.mp3, but when the resulting file is compared with diff, they are different compared to the 2 step process.

  I’m fairly new to ffmpeg, and have spent hours on the documentation without really knowing how to accomplish what i’m trying to do.

• Handling an arbitrary number of start and stop time pairings to cut a movie file down

  9 juin 2019, par Kieran

  I am writing a function that takes a list of tuples and a file path string as arguments and outputs a cut down video that only includes the frames that fall inside the start/stop pairings provided.

  I’m getting stuck because I am not sure whether the .trim() method of the ’infile’ object is altering the existing object or or creating a new one or doing something else entirely.

  the list of start/stop frame pairings can be arbitrarily long, every example I have found has been for a specific number of start and stop pairings and I can’t find anything describing what data structure needs to be passed back to ffmpeg.concat().

  My code is displayed below :

  import ffmpeg
  
  
  
  frameStamps = [(50,75),(120,700),(1250,1500)]
  
  videoFilePath = 'C:/Users/Kieran/Videos/testMovie.mp4'
  
  outputFolder = 'C:/Users/Kieran/Videos/'
  
  
  
  def slice_video(frameStamps, videoFilePath, outputFolder):
  
  
  
      originalFile = ffmpeg.input(videoFilePath)
  
  
  
      for stamp in frameStamps:
  
          ffmpeg.concat(originalFile.trim(start_frame=stamp[0], end_frame=stamp[1]))
  
  
  
  
  
      ffmpeg.output(outputFolder + 'testoutput.mp4')
  
      ffmpeg.run() 
  
  
  
  slice_video(frameStamps, videoFilePath, outputFolder)

  Now I am able to get the following when I individually print out originalFile.trim() which are getting recognised in the console as "FilterableStream" objects

  trim(end_frame=75, start_frame=50)[None] <29b4fb0736ec>
  
  trim(end_frame=700, start_frame=120)[None] <c66c4e1a48f5>
  
  trim(end_frame=1500, start_frame=1250)[None] &lt;13e0697a5288>  
  
  </c66c4e1a48f5>

  and I have tried passing them back as a list, dictionary and tuple and haven’t been able to get it working

  Output Errors :

    File "C:/Users/Kieran/Example.py", line 21, in slice_video
  
  ffmpeg.output(outputFolder + 'testoutput.mp4')
  
  
  
    File "C:\ProgramData\Anaconda3\lib\site-packages\ffmpeg\_ffmpeg.py", line 94, in output
  
  return OutputNode(streams, output.__name__, kwargs=kwargs).stream()
  
  
  
    File "C:\ProgramData\Anaconda3\lib\site-packages\ffmpeg\nodes.py", line 282, in __init__
  
  kwargs=kwargs
  
  
  
    File "C:\ProgramData\Anaconda3\lib\site-packages\ffmpeg\nodes.py", line 170, in __init__
  
  self.__check_input_len(stream_map, min_inputs, max_inputs)
  
  
  
    File "C:\ProgramData\Anaconda3\lib\site-packages\ffmpeg\nodes.py", line 149, in __check_input_len
  
  raise ValueError('Expected at least {} input stream(s); got {}'.format(min_inputs, len(stream_map)))
  
  
  
  ValueError: Expected at least 1 input stream(s); got 0