before language fix

_old_not_used/demo/worklets/audio-playback.js

@@ -0,0 +1,171 @@
+// @ts-check
+/**
+ * AudioWorkletProcessor that plays back Float32 mono samples received from
+ * the main thread, upsampling whatever incoming rate the server uses
+ * (typically 24 kHz PCM16) to the AudioContext rate (typically 48 kHz).
+ *
+ * Lifecycle / messaging:
+ *
+ *   main -> worklet:
+ *     { kind: "config", inputRate: 24000 }              one-shot at startup
+ *     { kind: "audio", samples: Float32Array }          (transferable) per chunk
+ *     { kind: "clear" }                                 wipe queue (barge-in)
+ *
+ *   worklet -> main:
+ *     { kind: "stats", queuedMs, played }               every ~250 ms
+ *     { kind: "underrun" }                              every time the queue
+ *                                                      runs dry mid-playback
+ *
+ * Underrun strategy: output silence. We do NOT hold the last sample (that
+ * tends to produce audible clicks/buzzes when long gaps appear between
+ * TTS chunks). A short ramp-out + ramp-in at boundaries would be nicer but
+ * the server's 30 ms cadence makes underruns visible only at end of turn.
+ */
+
+const STATS_INTERVAL_FRAMES = 12000;
+const FADE_FRAMES = 32;
+
+class AudioPlaybackProcessor extends AudioWorkletProcessor {
+  constructor() {
+    super();
+    this._inputRate = 24000;
+    this._stepRatio = this._inputRate / sampleRate;
+    this._queue = [];
+    this._readIdx = 0;
+    this._fracPos = 0;
+    this._playing = false;
+    this._framesSinceStats = 0;
+    this._totalPlayed = 0;
+    this._fadeIn = 0;
+    this._fadeOut = 0;
+    this._lastSample = 0;
+
+    this.port.onmessage = (e) => {
+      const data = e.data;
+      if (!data || typeof data !== "object") return;
+      switch (data.kind) {
+        case "config":
+          if (typeof data.inputRate === "number" && data.inputRate > 0) {
+            this._inputRate = data.inputRate;
+            this._stepRatio = this._inputRate / sampleRate;
+          }
+          break;
+        case "audio":
+          if (data.samples instanceof Float32Array && data.samples.length > 0) {
+            this._queue.push(data.samples);
+            if (!this._playing) {
+              this._playing = true;
+              this._fadeIn = FADE_FRAMES;
+              this._fadeOut = 0;
+            }
+          }
+          break;
+        case "clear":
+          this._queue.length = 0;
+          this._readIdx = 0;
+          this._fracPos = 0;
+          this._fadeOut = FADE_FRAMES;
+          break;
+      }
+    };
+  }
+
+  _queuedSamples() {
+    let total = -this._readIdx;
+    for (const buf of this._queue) total += buf.length;
+    return Math.max(0, total);
+  }
+
+  /** Linear-interp read at the current fractional position. */
+  _readInterpolated() {
+    if (this._queue.length === 0) return null;
+    const head = this._queue[0];
+    const idx = this._readIdx;
+    const frac = this._fracPos;
+
+    let a = head[idx];
+    let b;
+    if (idx + 1 < head.length) {
+      b = head[idx + 1];
+    } else if (this._queue.length > 1) {
+      b = this._queue[1][0];
+    } else {
+      b = a;
+    }
+    return a + (b - a) * frac;
+  }
+
+  /** Advance the read position by `stepRatio`; pop consumed buffers. */
+  _advance() {
+    this._fracPos += this._stepRatio;
+    while (this._fracPos >= 1) {
+      this._fracPos -= 1;
+      this._readIdx += 1;
+    }
+    while (this._queue.length > 0 && this._readIdx >= this._queue[0].length) {
+      this._readIdx -= this._queue[0].length;
+      this._queue.shift();
+    }
+  }
+
+  process(_, outputs) {
+    const channels = outputs[0];
+    if (!channels || channels.length === 0) return true;
+    const out = channels[0];
+    const stereo = channels.length > 1 ? channels[1] : null;
+
+    for (let i = 0; i < out.length; i++) {
+      let sample = 0;
+
+      if (this._playing) {
+        const v = this._readInterpolated();
+        if (v === null) {
+          // Underrun: try to ramp out cleanly to avoid clicks.
+          sample = this._lastSample * Math.max(0, 1 - 1 / FADE_FRAMES);
+          this._lastSample = sample;
+          if (Math.abs(sample) < 1e-4) {
+            this._playing = false;
+            this._lastSample = 0;
+            this.port.postMessage({ kind: "underrun" });
+          }
+        } else {
+          sample = v;
+          this._lastSample = v;
+          this._advance();
+        }
+
+        if (this._fadeIn > 0) {
+          const gain = 1 - this._fadeIn / FADE_FRAMES;
+          sample *= gain;
+          this._fadeIn -= 1;
+        }
+        if (this._fadeOut > 0) {
+          const gain = this._fadeOut / FADE_FRAMES;
+          sample *= gain;
+          this._fadeOut -= 1;
+          if (this._fadeOut === 0) {
+            this._playing = false;
+            this._lastSample = 0;
+          }
+        }
+
+        this._totalPlayed += 1;
+      }
+
+      out[i] = sample;
+      if (stereo) stereo[i] = sample;
+    }
+
+    this._framesSinceStats += out.length;
+    if (this._framesSinceStats >= STATS_INTERVAL_FRAMES) {
+      this._framesSinceStats = 0;
+      const queuedSamples = this._queuedSamples();
+      const queuedMs = (queuedSamples / this._inputRate) * 1000;
+      this.port.postMessage({ kind: "stats", queuedMs, played: this._totalPlayed });
+    }
+
+    return true;
+  }
+}
+
+registerProcessor("audio-playback", AudioPlaybackProcessor);