From theory to practice

[sparkz_alot]

A .wav file (as well as most other audio and images actually) consists of two main parts, a header and the actual data.  For a .wav file  the 'header' is 44 bytes (0 - 43) and the data is the remainder of the file (bytes 44 - end).  The 'header' is further divided into 'file' and 'format' bytes (chunks). The following is something I wrote to 'read' that information.  It's some what long as I included a lot of comments. It only requires the built-in struct module.  This is based on the information provided here: .WAV format.  Hope this help you in understanding what's going on 'under the hood'

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#! /usr/bin/env/ python3

import struct


"""
be = big endian, le = little endian followed by field(bytes) size
file_id = chunk 0-3; be, 4, ascii each character = 1 byte, default 'RIFF'
file_sz = chunk 4-7; le, 4, 32 bit integer, file size minus 8 bytes
file_type = chunk 8-11; be, 4, File type, default = 'WAVE'
file_format = chunk 12-15; be, 4, format chunk marker, default = 'fmt ', NOTE there is a space at the end of the chunk
format_data = chunk 16-19; le, 4, length of format data listed above, default 16 (8, 16, 24, 32)
format_type = chunk 20-21; le, 2, type of format, default 1 (PCM), other number indicates compression
num_ch = chunk 22-23; le, 2, number of channels, 1=mono, 2=stereo (up to 6 channels ?)
sample_rate = chunk 24-27; le, 4, sample frames per sec (i.e. Hz),default 44100 (CD quality)
byte_rate = chunk 28-31; = le, 4, (sample_rate * bits_sample * no_chan) / 8
blk_align = chunk 32-33; le, 2, (bits_sample * no_chan) / 8, rounded up to next whole number.
        (A sample frame for a 16-bit mono wave is 2 bytes. A sample frame for a 16-bit stereo wave is 4 bytes. Etc)
bits_sample = chunk 34-35; le, 2, bits per sample,  (ie, a 16-bit waveform would have wBitsPerSample = 16)
d_tag = chunk 36-39; be, 4, marks beginning of data, default = 'data'
data_sz = chunk 40-43; le, 4, size of data section; (number of samples * no_chan * bits_sample) / 8
"""


def main(w_file):

    with open(w_file, 'rb') as bif:
        bif.seek(0)
        file_id = str(bif.read(4), encoding='utf-8')

        bif.seek(4)
        sz = bif.read(4)
        file_sz = struct.unpack('<i', sz)

        bif.seek(8)
        file_type = str(bif.read(4), encoding='utf-8')

        bif.seek(12)
        file_format = str(bif.read(4), encoding='utf-8')

        bif.seek(16)
        fd = bif.read(4)
        format_data = struct.unpack('<2h', fd)

        bif.seek(20)
        ft = bif.read(2)
        fmt = struct.unpack('<h', ft)
        if fmt[0] == 1:
            format_type = 'PCM (Uncompressed)'
        else:
            format_type = 'Compressed'

        bif.seek(22)
        nc = bif.read(2)
        num_ch = struct.unpack('<h', nc)

        bif.seek(24)
        sr = bif.read(4)
        sample_rate = struct.unpack('<i', sr)

        bif.seek(28)
        br = bif.read(4)
        byte_rate = struct.unpack('<i', br)

        bif.seek(32)
        ba = bif.read(2)
        blk_algn = struct.unpack('<h', ba)

        bif.seek(34)
        bps = bif.read(2)
        bits_sample = struct.unpack('<h', bps)

        bif.seek(36)
        d_tag = str(bif.read(4), encoding='utf-8')

        bif.seek(40)
        ds = bif.read(4)
        data_size = struct.unpack('<i', ds)

        info = (file_id, file_sz[0] + 8, file_type, file_format, format_data[0], format_type, num_ch[0], sample_rate[0],
                byte_rate[0], blk_algn[0], bits_sample[0], d_tag, data_size[0])

    return info

if __name__ == '__main__':
    wav_file = 'SineWave_440Hz.wav'    # Make what ever wave file you'd like

    stats = main(wav_file)

    print("\n.WAV File information for ", wav_file)
    print("=" * 79, "\n")

    print("File ID: {} \nFile Size: {} \nFile Type: {} \nFile Format: {} \nLength of Format Data: {}"
          "\nType of Format: {} \nNumber of Channels: {} \nSample Rate: {} \nByte Rate: {} \nBlock Align: {}"
          "\nBits Per Sample: {} \nData Header: {} \nSize of Data Section: {}".format(
        stats[0], stats[1], stats[2], stats[3], stats[4], stats[5], stats[6], stats[7], stats[8], stats[9], stats[10],
        stats[11], stats[12]))

the output:

Output:
C:\Python36\python.exe C:/Python/Sound/read_wave.py

.WAV File information for  SineWave_440Hz.wav
=============================================================================== 

File ID: RIFF 
File Size: 264644 
File Type: WAVE 
File Format: fmt  
Length of Format Data: 16
Type of Format: PCM (Uncompressed) 
Number of Channels: 1 
Sample Rate: 44100 
Byte Rate: 88200 
Block Align: 2
Bits Per Sample: 16 
Data Header: data 
Size of Data Section: 264600

Process finished with exit code 0

I did not include the actual data, but concept remains the same.  Just 'seek(44), read the appropriate bits per sample (i.e . 8, 16, 24, 32) then unpack it.  Writing the file is pretty much just the reverse, except you 'pack' instead of 'unpack'.