Homebrew MusicPlayer Advance: ID-ing compression algorithm from 2003 homebrew

[therealbenwiley]

Hi there, I'm new to these forums, looking for folks who might know about GBA homebrew toolchains from 2003.

I came because I'm working on trying to reverse engineer the ROM-building process for MusicPlayer Advance, Neimod's 2003 WinAMP-inspired homebrew for GBA. I know there are better-maintained music player solutions like GSMPlayer, but I find MPA to be charming and the Windows software for converting audio and packing it into the ROM still works!

The (somewhat tedious) process goes like this:
1. Convert audio files to PCM (WAV) with specific bitrate and sample rate
2. Use MPAWRITE.exe to convert PCM to "MPA" format (mystery compression), one file at a time.
3. Use MPAWRITE.exe to insert a playlist of MPA format tracks into the music player ROM.

I'm a web dev and I want to build a web app that automates this whole process, so you upload a list of songs and it spits out a MusicPlayer Advance ROM with your music included.

I already successfully spec'd the format used for packing MPA into the ROM, but I haven't figured out what compression is used to convert PCM to the MPA format. I figured folks familiar with early GBA homebrew toolchains might be able to provide insights. Were there common types of file compression, or common audio file types, used for homebrew games at the time?

I have attached a folder with all the MusicPlayer Advance files, plus a text file where I describe the spec of the MPA audio storage in the GBA ROM, and also a before/after sample of PCM converted to MPA.

 

[Jayro]

Does this require any special hardware for music playback, or just a GBA with a flash cart?

 

[therealbenwiley]

Does this require any special hardware for music playback, or just a GBA with a flash cart?

Just anything to play GBA games (like a flash cart). The ROM is injected with audio files rather than loading them dynamically.

 

[OmDRetro]

I would like to know also.

I somewhat automated the process of making the ROM, but it still does require manual work to encode PCM files to NEiM0D's mysterious MPA codec.

I created a hacky approach to achieve a similar goal for the SCFW project

https://github.com/OmDRetro/MPA2-Compilation-Tools

 

[therealbenwiley]

I would like to know also.

I somewhat automated the process of making the ROM, but it still does require manual work to encode PCM files to NEiM0D's mysterious MPA codec.

I created a hacky approach to achieve a similar goal for the SCFW project

Did you try / were you successful writing MPA2 to a cartridge? This is a separate issue I've run into, I'm getting a blank screen (Game Boy but no Nintendo logo) when launching it on a GBA SP

 

[OmDRetro]

Did you try / were you successful writing MPA2 to a cartridge? This is a separate issue I've run into, I'm getting a blank screen (Game Boy but no Nintendo logo) when launching it on a GBA SP

Yep, already tested



My only problem now is automating the conversion from PCM to MPA.


EDIT:

As for booting this on a cartridge, the best way to perform UAT is to open the ROM itself in an emulator WITHOUT skipping the BIOS. It will let you know if the ROM passes the logo check(which means it can boot on a real cartridge). I learned this the hard way when I thought it had something to do with the BIOS

https://github.com/mgba-emu/mgba/issues/3227#issuecomment-2156436936

If the ROM fails the logo check, you must apply gbafix (this binary comes with the devkitarm toolchain). Once fixed, it should boot.

 

[therealbenwiley]

Ah I see you're using an SD cart. I should try with my Everdrive and see if that works. I was flashing with GBxCart RW to a single flash cart.

Post automatically merged: Aug 21, 2024

Thanks so much for the tip about gbafix. This was indeed what I needed and the ROM works now on my GBA. I had been running the built-in fixers proposed by FlashGBX which worked for others ROMs.

As for the format, I still have no idea.

Post automatically merged: Aug 21, 2024

Also, another thing I'd love to figure out, is how I could inject graphics into the ROM. I'd love to insert album art into the header. I opened the GBA file up in a tile editor (called "Tile Molester" (???)), I was able to make out an embedded array of alphanumeric characters as well as some pieces of the logo, but the graphics seem pretty mangled/compressed. I guess I could figure it out if I spend long enough drawing red pixels in random places, but it will require much trial and error.

 

[SylverReZ]

Does the MusicPlayer Advance have any sort of buffer overflow that can be performed on the audio files, similar to the Nintendo 3DS Sound? Perhaps try to find ways to expand the audio length or header to locate a flaw that could allow the execution of unsigned code (i.e., homebrew).

 

[npbg6464]

The audio compression is Dialogic ADPCM (aka VOX) [https://en.wikipedia.org/wiki/Dialogic_ADPCM]. Tools that use libsndfile (like Adobe Audition) support reading and writing it.

 

[OmDRetro]

The audio compression is Dialogic ADPCM (aka VOX) [https://en.wikipedia.org/wiki/Dialogic_ADPCM]. Tools that use libsndfile (like Adobe Audition) support reading and writing it.

I tried importing a converted PCM file(*.MPA) to Audacity. Since VOX is headerless and that its a raw sound file, I tried importing with the ff. settings:

The output audio is wrong. I can hear the music being played, but its as if only certain mid-low frequencies are captured. Also, I haven't tried SOX to see if that will make a difference in playback after conversion from VOX(Raw audio / Headerless) to the usual playback formats.

EDIT: I stumbled upon this discussion indicating that ADPCM can have a multitude of implementations/algorithms. Looks like we may be stuck with MPAWrite for a while.

 

[Rednorka]

I heard from a friend who attempted GBA sound modding that IMA ADPCM might work in this regard (unless you already tried it). Do avoid using Adobe Premier for the conversion though - it wrongly uses this name for VOX ADPCM format.

 

[OmDRetro]

I heard from a friend who attempted GBA sound modding that IMA ADPCM might work in this regard (unless you already tried it). Do avoid using Adobe Premier for the conversion though - it wrongly uses this name for VOX ADPCM format.

Thanks for the suggestion, but I think that somehow narrows it down. Much like what's mentioned in my last comment, there IS a multitude of compression algorithms/codecs.

Here's a small snip of a few ADPCM formats so far.

I'll take a look via trial and error to see which ones NEiM0D has likely used.