Two hardware-faithfulness fixes found by the always-on tap rings + Beetle
oracle A/B on fingerprint-matched attract music (tools/audio_pair_segments):
the recomp played the identical track at -3.8 dBFS vs the oracle's
-14.1 dBFS — +10.3 dB hot, clipping continuously.
1. spu.c: the voice repeat/loop address register (voice reg 7) is LIVE
state on real hardware — writing it after KEYON retargets where the
next END+REPEAT block jumps (Beetle spu.cpp:1150/333), and the block
auto-latch (flag bit 2) updates the guest-visible register (386/1302).
The recomp cached repeat_addr at KEYON only, so X5's driver idiom —
KEYON, then point the loop register at a silent tail block; no KEYOFF
ever — left voices looping the LOUD sample body forever. Measured: 3
stuck voices re-looping ~1400x/s, 160k SPU events/min vs the oracle's
633, zero game KEYOFF writes (the game never needs one), +11 dB.
2. cdrom.c: implement the CD controller's decode volume matrix
([src][port], 0x80 unity, pending banks + apply latch at 1F801803.3
bit 5 — mapping copied from Beetle cdc.cpp:1483-1501, applied after
the XA resample per PS1 hardware tests). X5 drives it constantly:
0x73-0x7E steady, ramped to 0x00 at scene changes (measured via the
new beetle `cdc_volume` command + PS_CDC::PSXRecomp_GetDecodeVolume
peek). Without it music fades never happened and steady level sat
~0.6 dB hot.
Also: AUDIO_TAP_VOICES (T0 voice-sum tap) for source-by-source mix
decomposition, per-tap WAV rates, bridge stats in audio_stats.
Measured after (MMX5 attract, 20-25 s windows):
spu_out RMS: -3.8 dBFS (clipping) -> -15.5 dBFS [oracle -14.1]
music-only chain already matched the oracle at -14.8 dBFS, confirming
decoder + mixer gain equivalence; the entire excess was stuck voices.
underruns: 2 events / 98 s (delivery fix holding).
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Matthew Stanley