Rip PCM samples from Roms?

#!/usr/bin/env python
"""

nibbledecode
Use this to convert the samples in e.g. Skate or Die 2 for NES or
any of several Game Boy games to wave format for other apps to use.

In Windows, save it as nibbledecode.py and drag raw files onto it.

Limitations: Master System/Game Gear nonlinear samples are not
supported.

(See copyright notice in versionMsg below.)


"""
from __future__ import with_statement, division
from contextlib import closing

usageMsg = "usage: %prog [options] infile.4bl [outfile.wav]"
descriptionMsg = """Expands 4-bit-per-sample linear PCM to an 8-bit wave file."""
versionMsg = """%prog 0.01
Copyright 2010 Damian Yerrick
Copying and distribution of this file, with or without modification,
are permitted in any medium without royalty provided the copyright
notice and this notice are preserved.  This file is offered as-is,
without any warranty.
"""

def expand4bit(src, little=False, signed=False):
    import array
    dst = array.array('B')
    xorData = 0x88 if signed else 0x08
    for byte in src:
        byte = ord(byte)
        s1 = (byte & 0xF0)
        s2 = (byte & 0x0F) << 4
        if little:
            s2, s1 = s1, s2
        dst.append(s1 ^ xorData)
        dst.append(s2 ^ xorData)
    return dst.tostring()

def main(argv=None):
    from optparse import OptionParser
    import wave

    if argv is None:
        import sys
        argv = sys.argv
   
    parser = OptionParser(usage=usageMsg, description=descriptionMsg,
                          version=versionMsg)
    parser.add_option('-l', '--little', dest='little',
                      default=False, action='store_true',
                      help='use low nibble first')
    parser.add_option('-s', '--signed', dest='signed',
                      default=False, action='store_true',
                      help='decode samples as signed nibbles')
    (options, args) = parser.parse_args(argv[1:])
    if len(args) not in (1, 2):
        parser.error("wrong number of arguments; try with --help")

    with open(args[0], 'rb') as infp:
        data = infp.read()
    data = expand4bit(data, little=options.little, signed=options.signed)
    outfilename = args[1] if len(args) > 1 else args[0] + '.wav'
    with closing(wave.open(outfilename, 'wb')) as outfp:
        outfp.setnchannels(1)
        outfp.setframerate(8372)
        outfp.setsampwidth(1)
        outfp.writeframes(data)

if __name__=='__main__':
    main()