Convert 3-byte stereo WAV-file to numpy array

Question

I have been given a large WAV-file of continuous underwater recording which I would like to convert to a numpy array for analysis. I am struggling to do this.

So far

Answer 1

For those with similar issues I post my solution. Note that this converts a 24-bit wave file into a signed floating point numpy array. Leave the /int2float part out when only converting to integers.

frames = wavfile.readframes(nsamples)

ch1 = np.zeros(nsamples)
ch2 = np.zeros(nsamples)
int2float = (2**23)-1

for x in np.arange(int(nsamples)):
    ch1_24bit_sample = frames[x*6:x*6+3]
    ch2_24bit_sample = frames[x*6+3:x*6+6]
    ch1_32bit_sample = bit24_2_32(ch1_24bit_sample)
    ch2_32bit_sample = bit24_2_32(ch2_24bit_sample)
    ch1[x]=struct.unpack('i',ch_32bit_sample)[0]
    ch2[x]=struct.unpack('i',ch_32bit_sample)[0]
    ch1[x]=ch1[x]/int2float
    ch2[x]=ch2[x]/int2float

def bit24_2_32(strbytes):
    if strbytes[2] < '\x80':
       return strbytes+'\x00'
    else:
       return strbytes+'\xff'