Weirdness with the Prototype Sonic 1 Sound Driver

Discussion in 'Engineering & Reverse Engineering' started by Alex Field, Feb 18, 2021.

  1. Alex Field

    Alex Field

    シュート! カオス・エメラルド・ザが消えようとしている! Member
    Downunda, Mobius
    Sonic the Hedgehog 2+, Sonic the Hedgehog 3+
    For those who don't understand the thread title, this is about all the strange oddities that the sound drive in the Sonic 1 prototype has; this was made before they tuned it to their liking, though quite frankly, some of the changes they made were surprising.
    • The WriteFMI and WriteFMII functions (sub_7272E/sub_72764) are the Type 1b versions, which the Sonic 1 sound driver is based on, EXCEPT that they went back to an (unoptimized) Type 1a version.
    • Has several more features, meaning this driver is superior to the final (again, it was tuned to their liking meaning some features were removed since they were unneeded).
    • Handles sound IDs <$80 in a different (and faster) way, which also makes support for music <$80 easier.
    • Although it can't be heard normally, there is a special function for sounds $D7>$DF which causes it to play a DAC sample ($D7=$81/Kick, $D8=$82/Snare etc...).
    • Handles music tempo differently, though the actual outcome is the same.
    Last edited: Feb 18, 2021