BlackMark 21f62d8288 Add audio-fidelity validator + fix mirror render under-run ...

Build coop_audio_validate, a tool that turns "the mirror audio sounds off"
into numbers. It plays a known sine (coop_tone, 44.1 kHz on a 48 kHz
endpoint -- the Godot/Brotato case), injects the hook as the host does, and
runs a fidelity analyzer (coop/tone_analysis.hpp: pitch error in cents,
SNR/THD, click + dropout counts), dumping a .wav to listen to. Modes:
--render drives the real AudioMirror and measures its rendered output;
--baseline/--selfcheck give the measurement floor; --listen <pid> records a
live coop_host's output; --wav analyzes a recording. Analyzer + WAV I/O are
unit-tested (tone_analysis_test) against synthesized defects.

Using it, the capture ring measures pristine (~68 dB, 0 gaps) while the
render path dropped to ~18 dB with gaps -- localizing a real defect in
AudioMirror::run_hooked: it re-primed (withheld the feed until ~30 ms had
rebuffered) on any partial fill (to_write < avail). A partial fill is normal
producer jitter, and withholding the feed drains the device, so a one-frame
ring dip became a full ~30 ms drop-out; on a jittery game it fired
constantly. Fix: feed whatever is available each tick and re-prime only on a
genuine starvation (device empty AND ring empty). The policy is factored
into a pure RenderPacer reused by run_hooked + run_loopback and proven by
render_pacer_test (the old policy withholds available data ~168x and drains
to one period from silence on a jittery schedule; the new one never
withholds).

ctest 17/17.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

2026-06-23 00:36:20 +02:00

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