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• Python extract wav from video file

  10 janvier, par xolodec

  Related :

  



  How to extract audio from a video file using python ?

  



  Extract audio from video as wav

  



  How to rip the audio from a video ?

  



  My question is how could I extract wav audio track from video file, say video.avi ? 
I read many articles and everywhere people suggest to use (from Python) ffmpeg as a subprocess (because there are no reliable python bindings to ffmpeg - the only hope was PyFFmpeg but i found it is unmaintaned now). I don't know if it is right solution and i am looking for good one.
  
I looked to gstreamer and found it nice but unable to satisfy my needs — the only way I found to accomplish this from command line looks like

  



   gst-launch-0.10 playbin2 uri=file://`pwd`/ex.mp4  audio-sink='identity single-segment=true ! audioconvert ! audio/x-raw-int, endianness=(int)1234, signed=(boolean)true, width=(int)16, depth=(int)16, rate=(int)16000, channels=(int)1 ! wavenc !  filesink location=foo.wav’ 


  



  But it is not efficient because i need to wait ages while playing video and simultaneously writing to wav file.

  



  ffmpeg is much better :

  



  avconv  -i foo.mp4  -ab 160k -ac 1 -ar 16000 -vn ffaudio.wav


  



  But i am unable to launch it from python (not as a command line subprocess). Could you please point me out pros and cons of launching ffmpeg from python as a command line utility ? (I mean using python multiprocessing module or something similar).

  



  And second question.

  



  What is simple way to cut long wav file into pieces so that i don't break any words ? i mean pieces of 10-20 sec length with start and end during the pause in sentences/words ?

  



  i know how to break them on arbitrary pieces :

  



  import wave


win= wave.open('ffaudio.wav', 'rb')
wout= wave.open('ffsegment.wav', 'wb')

t0, t1= 2418, 2421 # cut audio between 2413, 2422 seconds
s0, s1= int(t0*win.getframerate()), int(t1*win.getframerate())
win.readframes(s0) # discard
frames= win.readframes(s1-s0)

wout.setparams(win.getparams())
wout.writeframes(frames)

win.close()
wout.close()


  


• Python extract wav from video file

  31 octobre 2015, par xolodec

  Related :

  How to extract audio from a video file using python ?

  Extract audio from video as wav

  How to rip the audio from a video ?

  My question is how could I extract wav audio track from video file, say video.avi ?
  I read many articles and everywhere people suggest to use (from Python) ffmpeg as a subprocess (because there are no reliable python bindings to ffmpeg - the only hope was PyFFmpeg but i found it is unmaintaned now). I don’t know if it is right solution and i am looking for good one.
  I looked to gstreamer and found it nice but unable to satisfy my needs — the only way I found to accomplish this from command line looks like

   gst-launch-0.10 playbin2 uri=file://`pwd`/ex.mp4  audio-sink='identity single-segment=true ! audioconvert ! audio/x-raw-int, endianness=(int)1234, signed=(boolean)true, width=(int)16, depth=(int)16, rate=(int)16000, channels=(int)1 ! wavenc !  filesink location=foo.wav’ 

  But it is not efficient because i need to wait ages while playing video and simultaneously writing to wav file.

  ffmpeg is much better :

  avconv  -i foo.mp4  -ab 160k -ac 1 -ar 16000 -vn ffaudio.wav

  But i am unable to launch it from python (not as a command line subprocess). Could you please point me out pros and cons of launching ffmpeg from python as a command line utility ? (I mean using python multiprocessing module or something similar).

  And second question.

  What is simple way to cut long wav file into pieces so that i don’t break any words ? i mean pieces of 10-20 sec length with start and end during the pause in sentences/words ?

  i know how to break them on arbitrary pieces :

  import wave
  
  
  
  
  
  win= wave.open('ffaudio.wav', 'rb')
  
  wout= wave.open('ffsegment.wav', 'wb')
  
  
  
  t0, t1= 2418, 2421 # cut audio between 2413, 2422 seconds
  
  s0, s1= int(t0*win.getframerate()), int(t1*win.getframerate())
  
  win.readframes(s0) # discard
  
  frames= win.readframes(s1-s0)
  
  
  
  wout.setparams(win.getparams())
  
  wout.writeframes(frames)
  
  
  
  win.close()
  
  wout.close()

• How to xfade an accelerated stream into a stream of unchanged speed

  9 mars 2024, par Matthias Simon

  How to xfade one stream, that was speed up with setpts into another stream using ffmpeg ?

  


  The natural approach would be :

  


  ffmpeg
 -i a.mkv
 -i b.mkv
 -filter_complex "
   [0:v]setpts=0.2*(PTS-STARTPTS)[A_OUT];
   [A_OUT][1:v]xfade=duration=2:offset=10[out]" 
 -map '[out]'
 out.mkv


  


  but this always results in a 5x speed up of the second stream during the 2sec transition time of xfade. In other words, during xfade, the PTS definition of the first stream is used for the second stream.