1f38f1a7fb
feedback_/fbzm1_/fb_smooth_alpha_ were read every process() call but nothing ever wrote feedback_, so the path was silently inert. Git history shows this was a *muted* feature, not dead code: `feedback = v0 * feedbackGain` with feedbackGain 0.1f (MEMLCeliumAudioApp.hpp @d095688), then "0; //0.1f" — zeroed with the value kept in the comment — then the write was dropped entirely when the engine was ported to nisps/engines/ at the 2026-04-29 rewrite (8d0d47b). Operator decision: port it back, live at 0.1f. The tap is voice 0's own enveloped output, post-envelope and pre voice-1/mix/ shape — NOT the final output. This differs from PAFSynth's feedback shape; where the sibling and the reference disagreed, the reference won. Not schema-exposed: the reference hardcoded it, and MEMLCelium has no voice spaces to vary it by. If feedback depth becomes a research axis it wants to be a runtime parameter — noted, not built. Verification, and a gap worth recording: parity-check.sh PASSES (max delta 2.38e-7) but that is NOT evidence for this change — its harness only exercises PAFSynth and ChannelStrip, and the impulse baseline runs all-params-0.5, under which voice 0's sequencer never triggers, so v0_env stays 0 and the new write is 0 either way. That baseline is blind to this path, not a check on it. So it was cross-checked directly instead: sequencer params forced to trigger early, 4800 samples native vs WASM through the nisps_engine_* C ABI — native vs WASM max abs diff 1.19e-7 (tolerance 1e-5) all 4800 samples nonzero, finite, max amplitude ~0.99 (tanh-bounded) same run with gain forced to 0 diverges by up to 1.49 — not a no-op No fixture regenerated. nisps.wasm ships here because it is a tracked artifact under the Phase 0 freshness gate. Follow-up: the parity harness covers 2 of 8 engines. "Firmware and WASM share the same engines" is asserted repo-wide but tested narrowly.
127 KiB
Executable file
127 KiB
Executable file