test

wave_test3.py

# wave_test.py
# python 2.7 doesn't support 'with' on the wave module
'''
original wave:
https://dl.dropboxusercontent.com/u/3397495/wav/we_must_build_upwards.wav

original label file, generated by audacity
https://dl.dropboxusercontent.com/u/3397495/wav/wmbu_labels

'''
import wave
import struct

filename = "we_must_build_upwards.wav"
info_filename = 'wmbu_labels'



def print_temp(a,b,c):
    print('nseconds', a)
    print('mark_start', b)
    print('mark_end', c)

def get_sample_markers(info_filename):
    '''read info file'''
    def clean(i):
        strs = i.split('\t')[:2]
        return [float(i) for i in strs]

    with open(info_filename) as f:
        sample_markers = [clean(i) for i in f.readlines()]
    return sample_markers

def get_duration_from_params(wave_params):
    frate, nframes = wave_params[2:4]
    duration_seconds = float(nframes)/float(frate)
    print(frate, nframes, duration_seconds)
    return duration_seconds

sample_markers = get_sample_markers(info_filename)

'''test on one marker'''
mark_start, mark_end = sample_markers[0]
nseconds = mark_end - mark_start
print_temp(nseconds, mark_start, mark_end)

'''read original file'''
f = wave.open(filename)
wave_params = f.getparams()
nchannels, sampwidth, frate, nframes, comptype, compname = wave_params

duration_seconds = get_duration_from_params(wave_params)

# find start frame, end frame and n  (n samples)
start_frame = int(mark_start * frate)
end_frame = int(mark_end * frate)
n = end_frame - start_frame

print(start_frame, end_frame, n)

def generate_silence(duration):
    '''duration in seconds, forces to be divisible by nchannels
    assuming here nchannels is 2 - which is fine for my needs'''
    dframes = int(frate*nchannels*duration)
    return dframes if dframes%2 == 0 else drframes+1

f.setpos(start_frame)
data = f.readframes(n)


'''open destination for writing'''
wf = wave.open('destination.wav', 'wb')
wf.setparams(wave_params)

silent_frames = generate_silence(0)  
silent_data = "".join((wave.struct.pack('h', 0) for i in range(silent_frames)))
wf.writeframes(silent_data)
wf.writeframes(data)


wf.close()
f.close()