Adding silent frame to wav file using python

Question

First time posting here, lets see how this goes.

I trying to write a script in python which would add a second of silence in the beginning of the wav file, but so far been unsuccessfully in doing so.

What I was trying to do is read in the wav header and then adding a \\0 to the beginning using the wave module but that did not work quite well. Here is the code which is based from here http://andrewslotnick.com/posts/audio-delay-with-python.html

import wave
from audioop import add

def input_wave(filename,frames=10000000): #10000000 is an arbitrary large number of frames
    wave_file = wave.open(filename,'rb')
    params=wave_file.getparams()
    audio=wave_file.readframes(frames)
    wave_file.close()

    return params, audio

#output to file so we can use ipython notebook's Audio widget
def output_wave(audio, params, stem, suffix):
    #dynamically format the filename by passing in data
    filename=stem.replace('.wav','_{}.wav'.format(suffix))
    wave_file = wave.open(filename,'wb')
    wave_file.setparams(params)
    wave_file.writeframes(audio)

# delay the audio
def delay(audio_bytes,params,offset_ms):
    """version 1: delay after 'offset_ms' milliseconds"""
    #calculate the number of bytes which corresponds to the offset in milliseconds
    offset= params[0]*offset_ms*int(params[2]/1000)
    #create some silence
    beginning= b'\0'
    #remove space from the end
    end= audio_bytes        
    return add(audio_bytes, beginning+end, params[0])

audio_params, aduio_bytes = input_wave(<audio_file>)
output_wave(delay(aduio_bytes,audio_params,10000), audio_params, <audio_file>, <audio_file_suffics> )

Using the above code I get an error when I try to add the silence as the audio length is not the same as the input.

I am also quite new to audio processing so now I am just trying anything and see what sticks.

Any advice or ideas how to approach would be great :).

Also I am using python 2.7.5

Many Thanks.

Answer 1

There are libraries that can do these kind of audio manipulation easily with least amount of code. One such is pydub .

You can install pydub as below and detail about dependencies are here
pip install pydub

Using pydub , you can read different audio formats ( wav in this case), convert them to audio-segment and then perform manipulations or simply play it.

You can also create an silent audio-segment of set period and add two segment with '+' operator.

Source Code

from pydub import AudioSegment
from pydub.playback import play

audio_in_file = "in_sine.wav"
audio_out_file = "out_sine.wav"

# create 1 sec of silence audio segment
one_sec_segment = AudioSegment.silent(duration=1000)  #duration in milliseconds

#read wav file to an audio segment
song = AudioSegment.from_wav(audio_in_file)

#Add above two audio segments    
final_song = one_sec_segment + song

#Either save modified audio
final_song.export(audio_out_file, format="wav")

#Or Play modified audio
play(final_song)