molluskandClaude Opus 4.8
aa94e861b1
Add a dependency-free signal-analysis toolkit and a `specview` dev CLI to evaluate audio (especially echo cancellation) with objective numbers and a terminal spectrogram instead of ear alone. - src/dsp/: hand-written radix-2 FFT, Hann window, STFT, seeded test-signal generators (sine/log-sweep/white/pink/impulse), metrics (RMS/dBFS/peak/ERLE/ per-band energy), minimal WAV read+write, and a 24-bit-ANSI half-block spectrogram renderer (magma colormap, freq/time axes, dB legend, ASCII fallback). Pure layers have no I/O; only `wav` touches the filesystem. - src/bin/specview.rs: `gen` (conjure a test signal -> WAV), `show` (spectrogram + per-band energy summary), `erle` (broadband + per-band echo-return-loss between a before/after pair). - 27 unit tests (FFT correctness, ERLE landmarks, WAV round-trip, render shape). Verified end-to-end: log sweep renders as the expected exponential curve; a 20 dB-quieter copy reads +20.0 dB ERLE broadband and per band. Measurement substrate for upcoming AEC refinement (no shipped-path changes). Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>