audio - Python extract wav from video file

Question

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()

Answer 1

It is a very easy Task using ffmpeg with python subprocess and there is a reason why people are pointing to this solution as a good solution.

This is the basic command extracting audio from a given video File:

ffmpeg -i test.mp4 -ab 160k -ac 2 -ar 44100 -vn audio.wav

The Python Code is just wrapping this command:

import subprocess

command = "ffmpeg -i C:/test.mp4 -ab 160k -ac 2 -ar 44100 -vn audio.wav"

subprocess.call(command, shell=True)

You have to make sure that ffmpeg is a known task, so in your system environment variables, under path, the path to ffmpeg.exe should be listed, or you can just use the full path to the exe in your python code.