musescore_extractsts.py

import struct
import sys
import os

"""
extract opus files from Muse Sounds STS containers.
the STS format is very simple. no reverse-engineering required, just about
half an hour spent gazing at it in a hex editor.

it is as follows:

uint32				STS name length
char[nLen]			STS name
uint32				Number of files
Entry[nEntries]		File entries

File Entry:

uint32				Filename length
char[nLen]			Filename
uint32				File start offset
uint32				Reserved
uint32				File end offset
uint32				Reserved

all offsets are absolute, and the data is located right after the file entry table with no padding before or betweem.
"""

basename = os.path.basename(sys.argv[1]).rsplit(".", maxsplit=1)[0]

if not os.path.exists(basename):
    os.mkdir(basename)

def readString(f):
    sLen = struct.unpack("<I", fi.read(4))[0]
    sVal = fi.read(sLen).decode()
    
    return sVal

with open(sys.argv[1], "rb") as fi:
    title = readString(fi)
    nEntries = struct.unpack("<I", fi.read(4))[0]
    
    print(title)
    print(f"{nEntries} entries\n")
    
    for _ in range(nEntries):
        name = readString(fi)
        start, end = struct.unpack("<I4xI4x", fi.read(16))
        
        print(name)
        
        seek = fi.tell()
        fi.seek(start)
        data = fi.read(end - start)
        
        with open(f"{basename}/{name}", "wb") as fo:
            fo.write(data)
        
        fi.seek(seek)