wave_test.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
import collections

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

def get_params_object(wave_params):
    '''returns a namedtuple object to allow attribute access'''
    wparams = 'nchannels sampwidth frate nframes comptype compname'
    param_dict = dict(zip(wparams.split(), wave_params))
    param_object = collections.namedtuple('file_params', wparams)
    return param_object(**param_dict)

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_fparams():
    duration_seconds = float(f_params.nframes)/float(f_params.frate)
    print(f_params.frate, f_params.nframes, duration_seconds)
    return duration_seconds

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(f_params.frate * f_params.nchannels * duration)
    silent_frames = dframes if dframes%2 == 0 else dframes+1
    return "".join((wave.struct.pack('h', 0) for i in range(silent_frames)))

def get_slice_details(mark_start, mark_end):
    start_frame = int(mark_start * f_params.frate)
    end_frame = int(mark_end * f_params.frate)
    n = end_frame - start_frame
    print(start_frame, end_frame, n)
    return start_frame, end_frame, n

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()
f_params = get_params_object(wave_params)
duration_seconds = get_duration_from_fparams()

start_frame, end_frame, n = get_slice_details(mark_start, mark_end)
f.setpos(start_frame)
data = f.readframes(n)

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

silent_data = generate_silence(0)  
wf.writeframes(silent_data)
wf.writeframes(data)


wf.close()
f.close()