Entry 332

"The Mono option reaches the synthesizer: ccSetOutputMode and sdCommand 3"

2026-10-01audioui

Filescrates/piney-audio/src/driver.rscrates/piney-audio/src/lib.rscrates/piney-game/src/mode.rscrates/piney-game/src/main.rscrates/piney-game/src/session.rscrates/piney-game/src/world.rscrates/piney-game/src/area.rscrates/piney-game/src/desktop.rsdocs/engine/sound.md

The sound page's Unknown asked which sceHSyn_SetOutputMode value the stereo/mono option sends. Following it showed that the port dropped the option entirely. Addresses are INF SLUS_202.67 unless marked SNDBASE.

The chain:

1. The OPTION Sound page's Output row (desktop and The World) writes saveData.output (+0x8424): 0 Mono, 1 Stereo. A new save copies ccSnd.outputMode (+0x0c), which the ccSound constructor sets to 1 (0x00180ee4).
2. ccSaveData::SetSoundEnv calls ccSetOutputMode(output) (0x00178658).
3. ccSetOutputMode (0x001795f0) ignores the mode already in force and any value past 1. Otherwise it stores the mode and queues sdRemote[2] = 3 with sdData[2] = m.
4. The next sdCommand, case 3, sends ccSndCmd(0x100, m) (0x00181870).
5. SNDBASE's ccSoundFunc passes m to sceHSyn_SetOutputMode (SNDBASE 0x0d68). 0 is mono: both pan gains 128.

So Mono sends 0 and Stereo 1. piney-audio's synthesizer already had Synth::mono, the pan law for mode 0. Nothing set it: the menus' SoundEnv request carried output, but Event::Volumes left it out.

The port now carries it the game's way:

• Event::Volumes has output, from both menus and from a loaded save;
• Audio::set_output_mode calls Driver::set_output_mode, which is ccSetOutputMode;
• the driver's task, at sdCommand's place (after the master volume, before the reverb), sends Command::OutputMode(m);
• the engine sets synth.mono = m == 0.

The test is the_output_mode_goes_out_at_the_next_sd_command (piney-audio, driver). Stereo again, or 2, sends nothing. Mono goes out once, at the next frame. tools/sound_ee.py does not log ccSndCmd(0x100), so the driver fixture is unchanged.

Also: ccSeOffLoop's ids

The same Unknown list held ccSeOffLoop with an id outside 0-7, which would write other ccSound bytes (-1 into sqNum for -1). Its three callers in main and the four overlays are:

• ccSound::strSeEnd (0x00183ff8);
• gcmn ccBoss03::Affect (0x00489e58);
• gcmn ccBoss03::OnThinkLeafGrow (0x0048da7c).

Each passes an id kept from ccSeOn3DLoop (0-7, or -1 when no slot was free) and skips -1. None can pass one outside 0-7.