dsda-doom: the MIDI music chops, and FluidSynth's voices on the SPEs (2026-10-17 onward)
| Date | 2026-10-17 |
|---|---|
| Games | dsda-doom |
| batches | 2026-10-17-dsda-doom-sound, 2026-10-17-fluidsynth-spu-dsp, 2026-10-17-fluidsynth-309, 2026-10-17-speq-367-deadline-pool, 2026-10-19-ssdroot2-gameplay-profiles |
| sessions | 2026-10-25-session, 2026-10-25-session-0121 |
Symptom. With the music on, dsda-doom’s sound chopped: 1095-1335 ALSA underruns in a 60 s play run,
the music audibly breaking up.
Evidence. FluidSynth took 48% of dsda-doom’s CPU, about 40% of a PPE thread, interpolation alone 31%
(SPU-AUDIO.md, “Results on the PS3”). Earlier
sound-settings tries (batch 2026-10-17-dsda-doom-sound, Mesa ps3.225): tuned 340 underruns and 46
s of CPU in one run, OPL 1312 in its first.
Run (play, 60 s, GL) |
CPU a minute | Underruns | Batch |
|---|---|---|---|
| no music | about 29 s | 18 | batch 2026-10-17-fluidsynth-309 |
| stock FluidSynth on the PPE | 44.5-53 s | 1095-1335 | batch 2026-10-17-fluidsynth-spu-dsp, batch 2026-10-17-speq-367-deadline-pool |
| version 1 on the SPEs (libspeq 0.288) | 31.7 s | 1097 | batch 2026-10-17-fluidsynth-spu-dsp |
| version 2 (libfluidsynth3 +ps3.309, libspeq 0.318) | 31.8 s | 588 and 709 (stock 1231 and 1331 the same session) | batch 2026-10-17-fluidsynth-309 |
| version 2 on the shared deadline pool (libspeq 0.367) | 26.5 s | 465 (PPE 1095) | batch 2026-10-17-speq-367-deadline-pool |
The user listened to version 2: “night and day, spu makes a huge difference”; the glitches that remain line up with the game’s own frame stalls. The gameplay profile of 2026-10-19 still puts the synthesis at about 30% of the samples. In the played sessions of 2026-10-25 the OpenGL launcher counted 7.5 audible dropouts a minute (from 10322 underruns), the software launcher 35.9.
Open. The cause of what remains, and with it the default (D3: FluidSynth on the SPEs, OPL, or no music). The same SDL_mixer MIDI path plays OpenTTD’s music.