initial version

2026-03-05 16:51:28 +00:00
commit 5e7954ee24
31 changed files with 4832 additions and 0 deletions
@@ -0,0 +1,130 @@
+import { useEffect, useRef, useCallback } from 'react'
+import { PitchDetector } from 'pitchy'
+import { NOTES } from '../lib/theory'
+
+const MIN_CLARITY = 0.85
+const MIN_VOLUME  = 0.01
+const FFT_SIZE    = 4096   // larger = better frequency resolution
+const NOISE_FLOOR = -60    // dB — ignore bins quieter than this
+
+// Build 12-bin chroma from FFT power spectrum.
+// Restricts to guitar fundamental range and applies log compression.
+function computeChroma(freqData, sampleRate, fftSize) {
+  const chroma = new Float32Array(12)
+  const binHz  = sampleRate / fftSize
+
+  for (let bin = 2; bin < freqData.length; bin++) {
+    const freq = bin * binHz
+    if (freq < 75 || freq > 1400) continue   // guitar fundamentals only
+    const db = freqData[bin]
+    if (db < NOISE_FLOOR) continue
+
+    // Power (db/10) discriminates harmonics better than amplitude (db/20)
+    const power = Math.pow(10, db / 10)
+    const midi  = 12 * Math.log2(freq / 440) + 69
+    const pc    = ((Math.round(midi) % 12) + 12) % 12
+    chroma[pc] += power
+  }
+
+  // Log compression reduces dominance of very loud partials
+  for (let i = 0; i < 12; i++) chroma[i] = Math.log1p(chroma[i] * 100)
+
+  const max = Math.max(...chroma)
+  if (max > 0) for (let i = 0; i < 12; i++) chroma[i] /= max
+
+  return chroma
+}
+
+// Find the dominant pitch class in the bass range (guitar lowest notes).
+// This gives us a strong root-note hint for chord matching.
+function detectBassPC(freqData, sampleRate, fftSize) {
+  const binHz = sampleRate / fftSize
+  let maxPower = 0, bestMidi = -1
+
+  for (let bin = 2; bin < freqData.length; bin++) {
+    const freq = bin * binHz
+    if (freq < 75 || freq > 350) continue
+    const db = freqData[bin]
+    if (db < NOISE_FLOOR) continue
+    const power = Math.pow(10, db / 10)
+    if (power > maxPower) {
+      maxPower = power
+      bestMidi = Math.round(12 * Math.log2(freq / 440) + 69)
+    }
+  }
+  if (bestMidi < 0) return null
+  return ((bestMidi % 12) + 12) % 12
+}
+
+export default function AudioCapture({ onNote, onChroma, isListening }) {
+  const audioCtxRef  = useRef(null)
+  const analyserRef  = useRef(null)
+  const detectorRef  = useRef(null)
+  const timeBufRef   = useRef(null)
+  const freqBufRef   = useRef(null)
+  const rafRef       = useRef(null)
+  const streamRef    = useRef(null)
+
+  const stop = useCallback(() => {
+    if (rafRef.current)    cancelAnimationFrame(rafRef.current)
+    if (streamRef.current) streamRef.current.getTracks().forEach(t => t.stop())
+    if (audioCtxRef.current) audioCtxRef.current.close()
+    audioCtxRef.current = null
+  }, [])
+
+  const start = useCallback(async () => {
+    stop()
+    const stream = await navigator.mediaDevices.getUserMedia({ audio: true })
+    streamRef.current = stream
+
+    const ctx = new AudioContext()
+    audioCtxRef.current = ctx
+
+    const analyser = ctx.createAnalyser()
+    analyser.fftSize = FFT_SIZE
+    analyser.smoothingTimeConstant = 0.6   // smooth FFT over time
+    analyserRef.current = analyser
+
+    ctx.createMediaStreamSource(stream).connect(analyser)
+
+    timeBufRef.current = new Float32Array(analyser.fftSize)
+    freqBufRef.current = new Float32Array(analyser.frequencyBinCount)
+    detectorRef.current = PitchDetector.forFloat32Array(analyser.fftSize)
+
+    function tick() {
+      const timeBuf = timeBufRef.current
+      analyser.getFloatTimeDomainData(timeBuf)
+
+      const rms = Math.sqrt(timeBuf.reduce((s, v) => s + v * v, 0) / timeBuf.length)
+      if (rms >= MIN_VOLUME) {
+        // Pitch — used for key detection
+        const [freq, clarity] = detectorRef.current.findPitch(timeBuf, ctx.sampleRate)
+        if (clarity >= MIN_CLARITY && freq > 60 && freq < 4200) {
+          const midi       = Math.round(12 * Math.log2(freq / 440) + 69)
+          const pitchClass = ((midi % 12) + 12) % 12
+          onNote({ noteName: NOTES[pitchClass], pitchClass, freq, midi, clarity })
+        }
+
+        // Chroma + bass — used for chord detection
+        if (onChroma) {
+          const freqBuf = freqBufRef.current
+          analyser.getFloatFrequencyData(freqBuf)
+          const chroma = computeChroma(freqBuf, ctx.sampleRate, analyser.fftSize)
+          const bassPC = detectBassPC(freqBuf, ctx.sampleRate, analyser.fftSize)
+          onChroma(chroma, bassPC)
+        }
+      }
+
+      rafRef.current = requestAnimationFrame(tick)
+    }
+    tick()
+  }, [onNote, onChroma, stop])
+
+  useEffect(() => {
+    if (isListening) start().catch(console.error)
+    else stop()
+    return stop
+  }, [isListening, start, stop])
+
+  return null
+}