If stereo WAV file's both channels are identical, change format to mono for all files recursively

Raseliarison nirinA nirina at mail.blueline.mg
Sat Jul 19 10:53:17 CEST 2003


hi all,
i found an unanswered question at
http://www.faqts.com/knowledge_base/index.phtml/fid/538
with possible response below. i've tried to send it at
faqt.python but can't figure out how to edit the page. so i put it here.
i want to kwon if this can convert all wave file. is there other
encodage than 8 or 16 bits for .wav files?
any bug and comment are welcome

--
nirinA

#--------------stereo2mono-R.py---------------
'''stereo2mono-R.py
convert stereo to mono recursively
usage : python stereo2mono-R.py path-directory
'''

import os, sys

from stereo2mono import *

directory = sys.argv[1]
os.chdir(directory)

for name in os.listdir('.'):
    if name.endswith('.wav'):
        w = Stereo2Mono(name)
        if w.isStereo() == 1:
            print '%s is in stereo'%name
            print 'Check for %s samples in the audio frame'%SAMPLING
            w.CompareSampling()
            print 'Both channels seem to be identical'
            print 'Check all data frames and save to mono file'
            w.CompareAndSave()
            print 'Done'
        else:
            print '%s is already in mono'%name

    else:
        pass


#-----stereo2mono.py-----------
'''stereo2mono.py
convert a stereo wave to mono
if both channels are identical

http://www.faqts.com/knowledge_base/view.phtml/aid/12121/fid/538
'''

import wave, sys

FORMAT = {'11':'1b','12':'1h','21':'2b','22':'2h'}
# format for wave files encoded in 8 and 16 bits

SAMPLING = 128

class Stereo2Mono:
    '''open the wave file and get its parameters
        compare the channels
        it will be done in two steps.
        samples are first compared,
        then if the samples are identical
        further comparison is performed
        and the mono wave file created
        '''
    def __init__(self, name):
        self.name = name
        self.w = wave.open(self.name)

    def isStereo(self):
        if self.w.getnchannels() == 2:
            return 1
        else:
            return 0

    def format_in(self):
        self.fmt = ''.join((str(self.w.getnchannels()),
                            str(self.w.getsampwidth())))
        return FORMAT.get(self.fmt)

    def format_out(self):
        self.fmt = ''.join(('1',
                            str(self.w.getsampwidth())))
        return FORMAT.get(self.fmt)

    def Parameters(self):
        return self.w.getparams()

    def Compare(self, amplitude):
        if amplitude[0] == amplitude[1]:
            return 1
        else:
            return 0

    def CompareSampling(self):
        for s in range(0, self.Parameters()[3],SAMPLING):
            if self.Compare(wave.struct.unpack(
                self.format_in(),self.w.readframes(1))) == 1:
                pass
            else:
                print 'channels at %s are not identical,abort!'%s
                #sys.exit()
        print 'Samples pass test'

    def CompareAndSave(self):
        '''Compare all and save to mono'''
        self.w.rewind()
        self.chars = '/-\\|'
        self.Save = wave.open(self.name.split('.')[0]+
                              '-mono'+'.wav','w')
        self.newparams = (1,
                     self.Parameters()[1],
                     self.Parameters()[2],
                     self.Parameters()[3],
                     self.Parameters()[4],
                     self.Parameters()[5])

        self.Save.setparams(self.newparams)

        for i in range(1, self.Parameters()[3]+1):
            self.UnPack = wave.struct.unpack(
                self.format_in(), self.w.readframes(1))
            if self.Compare(self.UnPack) == 1:
                self.Save.writeframes(wave.struct.pack(
                    self.format_out(), self.UnPack[0]))
                sys.stdout.write(chr(13))
                sys.stdout.write('%s %i/%i     ' % (
                    self.chars[i % 4], i, self.Parameters()[3]))
                sys.stdout.flush()
            else:
                print 'Data at index %s are not the same, abort!'%i
        self.w.close()
        self.Save.close()

def main():
    try:
        name = sys.argv[1]

        w = Stereo2Mono(name)
        if w.isStereo() == 1:
            print '%s is in stereo'%name
            print 'Check for %s samples in the audio frame'%SAMPLING
            w.CompareSampling()
            print 'Both channels seem to be identical'
            print 'Check all data frames and save to mono file'
            w.CompareAndSave()
            print 'Done'
        else:
            print '%s is already in mono'%name

    except:
        print '''usage : python stereo2mono.py the-stereo-wavefile.wav\n
        the wave file must be encoded in 8 or 16 bits'''

if __name__ == '__main__':
    main()

# 030718 19:41:48 nirinA









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