Audio channels
Posted: Wed Jan 30, 2019 10:57 amMostly just thoughts since really I've never looked at the audio emulation. Currently it's a giant black box
But in the audio in sega rally 2 has some serious issues lol
The issue is, two separate tracks have been encoded in the left/right audio, and the system is choosing to just mirror one channel to the other.
Where would we even look to find out how its selecting this? There must be some register or something somewhere
But in the audio in sega rally 2 has some serious issues lol
The issue is, two separate tracks have been encoded in the left/right audio, and the system is choosing to just mirror one channel to the other.
Where would we even look to find out how its selecting this? There must be some register or something somewhere
For MPEG music, the DSB code is where you'll want to look, specifically CDSB2 for Sega Rally 2. The DSB classes actually perform their own mixing and re-sampling, so if the setting for channel selection is discovered, it should be pretty straightforward to fix. R. Belmont originally reverse engineered the DSB far enough to allow music to be played. You'll see a big switch statement that handles commands written by the DSB's processor (a Z80 for DSB1 and 68K for DSB2) to some hardware port. There is little rhyme or reason to how the commands appear structured and the assumption is that they form some sort of state machine. This state machine is where you'll want to poke around. It's pretty easy to break some obscure thing in a game (pay attention to things like volume fades). There are definitely un-handled or maybe even mis-handled commands. I suspect that for the offending music tracks (title + last stage) in srally2, some command is first sent that configures the channels. You'll definitely want to look at what happens during transitions from stereo tracks to the broken ones as well as the reverse transition. If there's a sound test menu, I'd start there.