F3M: Fast S3M playroutine for whatever, that also happens to work on the Game Boy Advance
Made in 2015 by GreaseMonkey - Public Domain
Test module is "Point of Departure" by Necros (pod.s3m), which you can get here (as it is not PD I've decided to post a link to it instead): http://lite.modarchive.org/module.php?55696
(While nintendo.bin is also not PD, it's a requirement in order to make this actually run on a GBA, and it's pretty small so it's included)
Building the GBA version:
You will need gcc and binutils for ARMv4T or higher. I personally use gcc-arm-none-eabi 4.8 2014q1 that is somewhere in FreeBSD's ports repository (try devel/gcc-arm-embedded).
For Windows, you'll have to read through gba_build.sh in a text editor.
For real OSes, run ./gba_build.sh in a terminal. It will spit out a file called gba_f3m.gba. Use that in your favourite emulator. (It works in Mednafen, VBA-M and Higan as of writing.) Or you could try it out on actual hardware!
Note, this will probably not work straight away, so you will have to edit gba_build.sh and make it use the right prefix for your ARM cross compiler. (When building on a Raspberry Pi, you would leave this blank.)
In order to change the module the test player uses, modify boot.S, do a different .incbin after s3m_beg, rebuild, and it should work just nicely.
Building the Open Sound System version:
You will need a C compiler that can be accessed by running cc.
Run ./oss_build.sh in a terminal.
This doesn't work on Windows. I made this simple player example for myself, and you can learn from it and adapt it to work for you.
TODO list:
- Most of the effects aren't implemented (heck, we don't even have vibrato), this should be fixed at some point
- Allow playback of oneshot samples by the audio engine
- DevKitARM or DevKitPRO or WhateverTheHellPeopleUSE support - I can never remember which one it is.
TODON'T list:
- Interpolation - if you want this, make an XM instead. And if you actually like XM, get out of my sight you filthy heathen!
- Workarounds for trackers like Modplug which think S3M can handle 16-bit samples and channel volumes and don't do that weird volume jump when you do an Rxy/tremolo effect - ST 3.21 is the one true authority here.
- Adlib channel support - we've got 32 cycles to mix 16 channels at 32768Hz on a GBA, do you really think this is even the slightest bit of a mildly good idea? (Answer: It's terrible. Go sit in the corner.)
- Any of the "optimisations" I've tried which just simply don't work on a GBA:
- Using a shift instead of a multiply for volume calculation - didn't notice any speed gain, but the audio sure sounded awful!
- Using a volume lookup table - code compiles to an MLA instruction without it, which is faster than doing LDRH then ADD
- Precaching more than one sample ahead - despite the fact that gamepak reads are kinda slow, this isn't the bottleneck!
- While it's possible to copy the module into fast RAM, it doesn't really improve things. It is supported, though (it's commented out).
TOMIGHTDO list:
- Proper stereo support. Not interested in getting this working on a GBA, however - this would require us to do 16 bytes per sample, which is slow!
- Big-endian support.
TOYOUDOIT list:
- Minimal players for other audio frameworks.