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• ffmpeg trim and fade audio in single command line

  27 février 2015, par Chandra Nakka

  How can i crop and fade out audio with ffmpeg at single command line.

  I’m using this command line :

  ffmpeg -i input.mp3 -y -af "atrim=start=10,afade=t=in:ss=0:d=15" output.mp3

  It just crop audio file. But I can’t get fade out effect.

  How to solve this problem ?

• Translating ffmpeg command line to C++ codec settings

  6 mars 2014, par pacificator

  I've been doing some work in ffmpeg for a while in C++.
  Most of the help regarding encoder settings is explained as command line options.
  For example (taken from the ffmpeg site) :

  -mbd rd -trellis 2 -cmp 2 -subcmp 2 -g 100 -pass 1/2’ 

  but beware the ’-g 100’ might cause problems with some decoders. Things to try :

   ’-bf 2’, ’-flags qprd’, ’-flags mv0’, ’- flags skiprd.

  This is not really usefull when you want to set these options in C.
  For example I managed to find int trellis ; in the AVCodecContext struct so that is one solved, but what about the others ?

  Is there a way to determine what command line parameters correspond to what AVCodecContext members ?
  I tried setting them like this :

  AVCodecContext* c;
  
  av_opt_set_int(c->priv_data, "cmp", 2, 0);

  But this returns an error code that the option does not exist.
  I've also tried :

    av_opt_set(c->priv_data, "cmp", "2", 0);

  I still get the error that the option does not exist.

  So, is there a way to determine what AVCodecContext members I should set that are equivalent to the ffmpeg command line parameters above ?

• Running ffmpeg on command line not working

  21 mai 2019, par machinery

  I would like to run a command over command line in Python. When I open cmd and issue the following command it works :

  ffmpeg -f concat -safe 0 -i C:\test\test.txt -c copy C:\test\out.MP4

  Now I try to run it in Python in the following way :

  from subprocess import check_call
  
  concat_list = "C:\\test\\test.txt"
  
  out_file = "C:\\test\\out.MP4"
  
  check_call(["ffmpeg", "-f", "concat", "-safe", "0", "-i", concat_list, "-c", "copy", out_file])

  When I do this I get the error "FileNotFoundError : [WinError 2] The system cannot find the file specified".

  What is my mistake ?

  The full error message is :

      'ffmpeg' is not recognized as an internal or external command,
  
  operable program or batch file.
  
      Traceback (most recent call last):
  
        File "C:/Users/xxx/Desktop/xxx/trunk/python/xxx/src/videos/processVideo.py", line 48, in <module>
  
          check_call(["ffmpeg", "-f", "concat", "-safe", "0", "-i", concat_list, "-c", "copy", out_file])
  
        File "C:\Users\xxx\AppData\Local\Continuum\anaconda3\lib\subprocess.py", line 336, in check_call
  
          retcode = call(*popenargs, **kwargs)
  
        File "C:\Users\xxx\AppData\Local\Continuum\anaconda3\lib\subprocess.py", line 317, in call
  
          with Popen(*popenargs, **kwargs) as p:
  
        File "C:\Users\xxx\AppData\Local\Continuum\anaconda3\lib\subprocess.py", line 769, in __init__
  
          restore_signals, start_new_session)
  
        File "C:\Users\xxx\AppData\Local\Continuum\anaconda3\lib\subprocess.py", line 1172, in _execute_child
  
          startupinfo)
  
      FileNotFoundError: [WinError 2] The system cannot find the file specified
  
  </module>