CHANNELS = 16
    SAMPLE_LENGTH = CHANNELS // 8
    BYTES_PER_SAMPLE = CHANNELS // SAMPLE_LENGTH
    BUFFER = 16386
    PROCNUM = 4

    vals = {}
    for i in range(2**16):
        vals[struct.pack('H', i)] = tuple(b'1' if e == '1' else b'0' for e in list("{:016b}".format(i)))

    with open('largefile.dat', 'rb') as f:
        data = f.read()
    size = len(data)
    print("Data size: %d" % size)

    out_file = open('largefile_dump2.dat', 'wb')
    out_list = [out_file]*CHANNELS

    samples = []

    for i in range(0, size // 8, SAMPLE_LENGTH):
        # if i % (1024**2) == 0: print("i = %d" % i)
        samples.append(vals[data[i:i+2]])
        if len(samples) >= BUFFER:
            samples = np.matrix(samples).transpose().tolist() # comment if no numpy
            for channel in range(CHANNELS):
                s = b''.join(samples[channel])                # comment if no numpy
                # s = b''.join(r[channel] for r in samples)   # uncomment if no numpy, don't forget to change the buffer to 256, otherwise slooow.
                out_list[channel].write(s)
            samples = []

    if samples:
        for channel in range(CHANNELS):
            s = b'\n'.join(r[channel] for r in samples)
            out_list[channel].write(s)

    out_file.close()