Considering the internet has been down for me the past 2 days and I had some time, I decided to do some poking around with the game ROMs from Data East 3 and Williams WPC systems. This thread focuses on the Data East system. I found some recoverable DMD images and sound effects/voices as well as text and I'll outline what I did below to dig them up. It's going to get long and technical but it's very interesting stuff.
Here I'm specifically looking at Lethal Weapon 3. In the version 2.08 ROM set on IPDB there is the CPU ROM (lw3cpuu.208), 3 sound/music ROMs (lw3u7.dat, lw3u17.dat, and lw3u21.dat), and 2 DMD ROMs (lw3drom0.a26 and lw3drom1.a26).
Obviously the CPU ROM contains mainly game code but I was able to find a few text strings by viewing lw3cpuu.208 with a hex editor. I've listed them along with their offsets:
A43E: LW3 11/17/92 USA CPU 2.08
BALLY WULFF 511-358-5343
AVRANCHE 33 58 58 10
ADONBOLAGEN AB 031-124570
IVEK (041) 447-008
DATA EAST CORP. 03-5370-0708
NORIVENDCO A/S 02-1608 30
NOVOMAT A.G. 062-61-40-61
OZ-SAGIE LTD 052-501641
VIDEOGAMES AB 036-1885 75
TECHNOPLAY ITALY 011-39-51416934
TAB AUSTRIA 43-72-294-5910
AMUSEMENT GAMES 61-2-740-550
DATAEAST SERVICE 1-800-KICKERS
I didn't bother to list the offsets of the last few since they're roughly in the same location of the file. The first string is the game name, date, and CPU version shown on startup. The second string is the six default player initials, and I've confirmed this:
1-800-KICKERS was Data East's service phone number, still used by Stern today. Bally Wulff refers to Bally Wulff Amusements, which was Bally's German subsidiary at the time. I can't think of a reason why this would be listed here as they couldn't have been an overseas distributor because they were direct competition, and they didn't get bought out until 1995 (there is some interesting history behind that on Wikipedia's Bally Technologies page). But I digress. The remaining text lists other possible foreign distributors/affiliates and phone numbers(?) but I'm not going to spend the time to research them. Also, some of the numbers may be incorrect due to trailing bytes.
This is where things get interesting. Of the 3 sound/music ROMs just by poking around I've found out that 2 of them (lw3u17.dat and lw3u21.dat) contain music, speech and instrument samples for the sequenced music. These are both 256kb. The third file, lw3u7.dat, appears to contain other data such as the music tracks themselves, pointers for sound data, etc. judging by the smaller file size (32kb).
To explore the 2 sound data files I used Audacity and imported them as raw data. It turns out that these ROMs do contain uncompressed audio (8-bit signed mono PCM at 8KHz) so that's pretty easy to get to. By the way, it's important that you get the encoding settings right or you will end up with garbage noise (top) vs. good usable sound (bottom):
These files are just PCM audio streams, sweet and simple. There is some garbage here and there but 95% of the file is just sound samples back-to-back. There were a few samples I couldn't properly decode though but could still make out ("Extra ball is lit" and Murtaugh saying "Diplomatic immunity revoked" and "Nyahahaha!"). I know the BSMT2000 (which happens to stand for "Brian Schmidt's Mouse Trap") also supports a custom compressed ADPCM format in addition to uncompressed PCM sound, so I'm assuming these are encoded as such. I have to slow the speed down to 4KHz to hear them properly, which suggests the encoding is a 4-bit ADPCM format (not that uncommon for the time).
So theoretically this means one COULD replace segments of these files with custom sounds/speech and musical instruments, flash the files back to ROM chips, and use them in their game. But the sound format and quality would have to be the same, and the lengths of the sounds couldn't be any longer than what was originally used in the game. I might think about trying this sometime with PinMAME and see where I get. Heck, I encourage other nerdy pinheads to try this too and if you're successful, actually develop a program that can take and convert short sounds and inject them into the ROM files. At least we will finally be able to get rid of Leo's annoying "Ok, ok, ok" lines.
Other interesting sound tidbits. I could take the instrument samples and "Data East-ify" any MIDI file or other sequenced music if I took the time to. Plus, I also looked at Tales from the Crypt's sound ROMs and they use more of the custom ADPCM encoded sounds as well as some 16KHz PCM sounds for slightly better quality.
For the DMD ROMs (lw3drom0.a26 and lw3drom1.a26) I used Tile Molester, a free program written in Java that can view any file as an image. Like the sound data, I can only view uncompressed bitmap images in the DMD ROMs. These are 2-bit color bitmaps which support up to 4 colors per pixel. Unfortunately due to spacing and alignment issues in Tile Molester I wasn't able to view anything in full resolution, but I did find a lot of things, such as the helicopter used in one of the stunt scenes:
I wish there was more I could do with the DMD data but besides running the game in PinMAME there really isn't. The editor doesn't view the images properly so I can't extract or try to replace anything. It's still cool, nonetheless.
Well that's it so far. Has anyone else been "poking around" as much as I have? Haha!