Technictix .mus file rearranging and converting script

technictix_mus.py

#Simple python script that implements almendaz's algorithm from https://hcs64.com/mboard/forum.php?showthread=60921&showpage=2

#Requires pydub

import sys
import io
import os

from pydub import AudioSegment

#User args
argc = len(sys.argv)
if argc < 2:
    exit("Usage : " + sys.argv[0] + " filename.mus [channels]")

channels =  int(sys.argv[2]) if (argc == 3) else 2

#Opening the .mus file
file = open(sys.argv[1], 'rb')

filesize = os.stat(sys.argv[1]).st_size

#See https://hcs64.com/mboard/forum.php?showthread=60921&showpage=2 and https://hcs64.com/mboard/forum.php?showthread=54118&showpage=0#post_54235
size = 0x2EE00
filler = 0x200
interleave = 0x17700
offset = (size + filler) * (channels / 2)

chan1 = open('chan1.mus', 'wb')
chan2 = open('chan2.mus', 'wb')
chan3 = -1
chan4 = -1
if channels == 4:
    chan3 = open('chan3.mus', 'wb')
    chan4 = open('chan4.mus', 'wb')

print("filesize : " + str(filesize))
chunks = int(filesize // offset)
print(str(chunks) + " chunks")

lim_l = 0
lim_r = 0

if chunks%2 ==0:
    lim_l = chunks - 2
    lim_r = chunks - 1
else:
    lim_l = chunks - 1
    lim_r = chunks - 2



i = 0
#First we read the odd chunks (chunk 1, chunk 3, chunk 5...)
while i <= lim_l:
    print("i: " + str(i))
    print( str(file.tell()) + '-', end='')
    
    out_l = file.read(interleave)
    chan1.write(out_l)
    out_r = file.read(interleave)
    chan2.write(out_r)
    
    if channels == 4:
        #Don't forget to take in account the 0x200 space of void
        file.read(filler) 
        out_l = file.read(interleave)
        chan3.write(out_l)
        out_r = file.read(interleave)
        chan4.write(out_r)
        
    file.read(filler)
    print(str(file.tell()))
    i += 2
    if i <= lim_l:
        file.seek(int(offset), 1)

i = lim_r
#Then we read the even chunks (chunk 2, chunk 4, chunk 6...) by going in the reverse order (16 -> 14 -> 12...)
while i >= 1:
    print("i: " + str(i))
    print( str(file.tell()) + '-', end='')
    out_l = file.read(interleave)
    chan1.write(out_l)
    out_r = file.read(interleave)
    chan2.write(out_r)
    if channels == 4:
        file.read(filler)  
        out_l = file.read(interleave)
        chan3.write(out_l)
        out_r = file.read(interleave)
        chan4.write(out_r)
    file.read(filler)
    print(str(file.tell()))
    i -= 2
    #go backwards by the block we just read AND the ones we already handled
    if i >=1:
        file.seek(int(-offset*3), 1)

    #Merging the channels together
    one = AudioSegment.from_file("chan1.mus", format='raw', frame_rate=24000, channels=1, sample_width=2)
    two = AudioSegment.from_file("chan2.mus", format='raw', frame_rate=24000, channels=1, sample_width=2)
    if channels == 2:
        res = AudioSegment.from_mono_audiosegments(one, two).export( sys.argv[1] + '.wav', format='wav')
    if channels == 4:
        three = AudioSegment.from_file("chan3.mus", format='raw', frame_rate=24000, channels=1, sample_width=2)
        four = AudioSegment.from_file("chan4.mus", format='raw', frame_rate=24000, channels=1, sample_width=2)
        res = AudioSegment.from_mono_audiosegments(one, two, three, four).export( sys.argv[1] + '.wav', format='wav')