Root cause: BIOS music engine reads voice register 6 (byte offset 0x0C,
CURVOL / ADSR_LEVEL) to find a free voice; recomp returned the never-
written spu_regs value (always 0), so the engine saw every voice as
silent and over-recycled voices 0-3 instead of fanning across all 24.
After fix, recomp KEYON-per-voice counts match Beetle exactly (e.g.
v0 2/2, v18 2/2, v22 1/1).
Also:
- Full ADSR envelope (Attack/Decay/Sustain/Release) ported from Beetle's
CalcVCDelta/RunEnvelope. KEYOFF now triggers Release-phase decay
rather than immediate silencing.
- End-without-loop triggers Release (matches RunDecoder), not active=0.
- ENDX latch at 0x1F801D9C/9E now reports actual block-end-reached
state instead of active-mask.
- SPU event ring (KEYON/KEYOFF/END_STOP/END_LOOP) on both backends with
frame-stamped per-voice payload; 1 M entries each (32 MB) for chime +
game-scene headroom. Beetle-side env>0 filter so silent-loop noise
doesn't bury the audible-voice timeline (matches recomp behavior
where deactivated voices don't fire further events).
- spu_voices / spu_events / spu_events_reset debug-server commands on
both ports. send_fmt buffer kept single-shot to avoid extra newlines.
- tools/_spu_ring_diff.py: frame-aligned event-ring diff with per-voice
count summary; chunk-count cap removed (was aborting reads at 98 KB).
- tools/_spu_capture.py, _spu_probe.py, _probe_one.py: targeted probes
used during diagnosis.
Local-only beetle-psx change (gitignored): same env>0 filter at
mednafen/psx/spu.cpp around line 345/352. Rebuild beetle-psx static
lib if reapplying.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Matthew Stanley