Scripts to convert SNES ROMs to SNES Classic (.sfrom) format and to read .sfrom headers

sfc2sfrom.py

#!/usr/bin/env python

# Permission to use, copy, modify, and/or distribute this software for any
# purpose with or without fee is hereby granted.
#
# THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH
# REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
# AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
# INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
# LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR
# OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
# PERFORMANCE OF THIS SOFTWARE.

import argparse
from struct import pack


def get_header_page(rom_format):
    """Returns the page containing the SNES header based on the ROM format"""
    is_hirom = rom_format - 0x14
    return 0x7000 + is_hirom * 0x8000


def get_format(data):
    """Returns 0x14 for LoROM and 0x15 for HiROM"""

    # Kind of lazy way of detecting this
    if all(31 < char < 127 for char in data[0x7FC0:0x7FC0 + 21]):
        return 0x14
    if all(31 < char < 127 for char in data[0xFFC0:0xFFC0 + 21]):
        return 0x15
    return None


def get_preset_id(data, header_page):
    """Returns a preset ID for some known games, otherwise 0x0"""

    addr = header_page + 0x0FC0
    name = data[addr:addr + 21].decode('ascii').strip()

    if data[header_page + 0x0FD6] == 0x03:
        return 0x10BD  # DSP-1 Games
    elif name == "MEGAMAN X2":
        return 0x1117
    elif name == "MEGAMAN X3":
        return 0x113D

    # Nothing special
    return 0x0


def get_super_fx(data, header_page):
    """Returns 0x0C if the ROM uses a Super-FX chip, otherwise 0x0"""

    # Games that use Super-FX chips have these ROM types
    SFX_TYPES = [0x13, 0x14, 0x15, 0x1a]

    addr = header_page + 0x0FD6

    if (data[addr] in SFX_TYPES):
        return 0x0C
    else:
        return 0x0


if __name__ == "__main__":
    parser = argparse.ArgumentParser(description="""Converts SNES ROMs to .sfrom for
                                                  the SNES Classic""")
    parser.add_argument('input', type=argparse.FileType('rb'))
    parser.add_argument('output', type=argparse.FileType('wb'))
    args = parser.parse_args()

    # Read in entire file because who needs RAM
    rom = args.input.read()
    args.input.close()

    # Strip out potential header
    rom = rom[len(rom) % 0x400:]

    # Simple header format
    # Start Size Type Contents
    # 0x00  0x04 I    0x100
    # 0x04  0x04 I    File size
    # 0x08  0x04 I    0x50
    # 0x0C  0x08 8x   0x0
    # 0x14  0x04 I    0x30
    # 0x18  0x19 25x  0x0
    # 0x31  0x04 I    ROM Size
    # 0x35  0x08 8x   0x0
    # 0x3D  0x02 H    Game preset ID
    # 0x3F  0x01 B    0x02
    # 0x40  0x01 x    0x0
    # 0x41  0x01 B    ROM format (hi/lo)
    # 0x42  0x01 B    Super-FX ? 0x0C : 0x0
    # 0x43  0x0D 13x  0x0

    rom_format = get_format(rom)
    if not rom_format:
        print("Can't get ROM format. Corrupted?")
        args.output.close()
        quit(-1)
    header_page = get_header_page(rom_format)

    header = pack('<3I8xI25xI8xHBx2B13x',
                  0x100,
                  len(rom) + 0x50,
                  0x50,
                  0x30,
                  len(rom),
                  get_preset_id(rom, header_page),
                  0x02,
                  rom_format,
                  get_super_fx(rom, header_page))

    args.output.write(header + rom)
    args.output.close()

sfromparse.py

#!/usr/bin/env python

from struct import unpack
from collections import namedtuple
import argparse

parser = argparse.ArgumentParser()
parser.add_argument('filename', type=str)
args = parser.parse_args()

filename = args.filename

f = open(filename, "rb")

header = f.read(0x30)
SNES_header = namedtuple('Header', 'const1 filesize const2 endofrom footeraddr footer eof unknown gid')
unpacked = SNES_header._make(unpack('<7I4xI8s4x', header))

print('File: ' + filename)
print('\nHeader: ')

for k, v in unpacked._asdict().iteritems():
    if type(v) is str:
        print(k + ":    \t  " + v)
    else:
        print(k + ":    \t0x" + format(v, '08X'))

f.read(unpacked.footer - 0x30)
footer = f.read(0x22)
SNES_footer = namedtuple('Footer', 'emuspeed romsize pcmsize footersize presetid unknown1 vol romtype unknown2 unknown3')
footunpacked = SNES_footer._make(unpack('<B3IH3B8x2I', footer))

print('\nFooter: ')

for k, v in footunpacked._asdict().iteritems():
    if type(v) is str:
        print(k + ":    \t  " + v)
    else:
        print(k + ":    \t0x" + format(v, '08X'))

i have figured out how to use this to convert sfc to sfroms but how do you convert smc to sfrom whats the command?

A common pattern i'm seeing using the newer revisions of the script break the 2nd controller input.
Using your 2nd revision which allows lorom/hirom choice is the last revision which 2nd controller input still works.

Interesting! I bet one of the values I'm omitting from the header is related to that somehow. I wonder which one. I'd probably guess footer offset 0x0F since that's usually 0x02.

Yep, that was the issue. The script is fixed now, at least according to Mortal Kombat 2.

I cleaned up the script a little and added support for the DSP-1 games that pcm720 listed. I only tested with Pilotwings though.

I looked at more DSP-1 games just to be sure. Turns out some games use 0x05 at offset 0x?FD6:

0x03:
Michael Andretti's Indy Car Challenge
Pilotwings
Lock On
Super Air Diver 2 (Japan-exclusive sequel to Lock On)
Suzuka 8 Hours (U)

0x05:
Super Mario Kart
Battle Racers
Final Stretch
Super 3D Baseball (Super Bases Loaded 2)
Suzuka 8 Hours (J)
Ballz 3D

I wonder if any non-DSP-1 games use those ROM types also.

This page has a lot of useful info about special chip types:
https://everything2.com/user/malcster/writeups/Super+Nintendo+Entertainment+System

To detect whether a ROM uses the DSP-1, then open it in a hex editor such as frhed. If it is a LoRom then check the location $7FD5 - a value of 0x20, 0x21, 0x30 or 0x31 indicates some kind of a DSP-1. If you need confirmation, also check location $7FD6: A value of 0x3 or 0x5 indicates a DSP-1 of some kind. If you are working with a HiRom, then do the same as above, except use the locations $FFD5 and $FFD6.

There's also information on Cx4:

To detect a C4 chip, look for 0x20 in $XFD5 and 0xF3 in $XFD6.

Could you add instructions on how to use this? I drag my rom on the .py and a black screen comes up but nothing happens :(