Entry 82

libsnd ticks are vblanks; 14 sequencer voices

2026-10-154maudio

FilesCargo.lock crates/rugrats/src/audio/sound.rs docs/engine/sound.md

Two of the sound's open points, from the sound init (0x8006e7e8) and the VSync callback, now in the port through retro_rt 8dd8b57 (its worklog 17).

• The crossfade's length (71's question): the init sets SsSetTickMode(0x1000) (0x800a8f58), SS_NOTICK. The game's VSync callback (0x800192b4) calls SsSeqCalledTbyT (0x800a48b8) every vblank, and that steps each SEQ's crescendo and decrescendo linearly (0x800a4b28). So a room's switch over 30 ticks is half a second, as the port had assumed; it is no longer a guess.
• The sequencer's voices: the init's SsSetReservedVoice(14) (0x800ad588) limits libsnd's allocator to voices 0-13; effects key on 17-23 directly. The port had let songs take 0-16. It now calls libsnd::Spu::set_reserved_voices(14), so a busy song steals among 14 voices, as on the PlayStation.
• Vibrato, portamento and reverb, which libsnd does not model, matter little here: none of the game's 1779 tones has vibrato or portamento, and one has the reverb bit.
• Checks: 64 tests pass; the menu's song 0 renders as before (peak 15581, RMS 2026).