Entry 71

Room songs crossfade

2026-10-154maudio

Filescrates/rugrats/src/audio/sound.rs crates/rugrats/src/app/mod.rs crates/rugrats/src/app/play.rs crates/rugrats/src/app/flow.rs crates/rugrats/src/world/game/rooms.rs crates/rugrats/src/world/game/mod.rs docs/engine/sound.md

A room's song now crossfades as 0x8006efcc does (docs/engine/sound.md, A room's song). Before, the port switched songs at once.

• Spu keeps two song slots: the one playing and one fading out. Each has a live volume and a fade.
  • switch_song(song, id, volume, 30): the playing song fades from its volume to 0 while the new one fades from 0 to the music volume, both over 30 libsnd ticks. The old one stops at 0.
  • Asking for the song playing, or the one fading out, does nothing. A switch during a fade drops the fading song first.
• Song volume is now applied as the voices mix, not baked in at note-on. The fades and SsSeqSetVol (the Audio menu's live music volume) also change notes already sounding.
• Game has room_song for RoomChange's switch, apart from song, which the level scripts start at once (MidiPlaySong). Only 0x80077a54 calls 0x8006efcc.
• Test (audio::sound::tests::a_room_switch_crossfades, the menu set's songs 0 and 1):
  • Halfway, both are near 45 of 90.
  • Asking again for the fading song changes nothing.
  • At the end, only the new song is left, at 90.