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<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8" />
  <meta name="viewport" content="width=device-width, initial-scale=1.0" />
  <title>Textual Echo Cancellation (TEC) — Interactive Demo</title>
  <style>
    :root {
      --bg: #f8fafc;
      --card: #ffffff;
      --border: #e2e8f0;
      --text: #0f172a;
      --muted: #475569;
      --primary: #2563eb;
      --primary-hover: #1d4ed8;
      --success-bg: #ecfdf5;
      --success-border: #10b981;
      --warn-bg: #fffbeb;
      --warn-border: #f59e0b;
    }
    * { box-sizing: border-box; }
    body {
      margin: 0;
      font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
      background: var(--bg);
      color: var(--text);
      line-height: 1.5;
    }
    .container {
      max-width: 1140px;
      margin: 0 auto;
      padding: 28px 20px 48px;
    }
    .header {
      background: var(--card);
      border: 1px solid var(--border);
      border-radius: 14px;
      padding: 24px 28px;
      margin-bottom: 24px;
      box-shadow: 0 1px 3px rgba(15, 23, 42, 0.04);
    }
    .header h1 {
      margin: 0 0 8px;
      font-size: 1.75rem;
      display: flex;
      align-items: center;
      gap: 10px;
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      margin: 8px 0;
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      font-size: 0.96rem;
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    .badges {
      display: flex;
      flex-wrap: wrap;
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      font-weight: 600;
      text-decoration: none;
      border: 1px solid #bfdbfe;
    }
    .badge-link:hover {
      background: #dbeafe;
    }
    .grid {
      display: grid;
      grid-template-columns: 1fr 1fr;
      gap: 24px;
    }
    @media (max-width: 860px) {
      .grid { grid-template-columns: 1fr; }
    }
    .panel {
      background: var(--card);
      border: 1px solid var(--border);
      border-radius: 14px;
      padding: 22px 24px;
      box-shadow: 0 1px 3px rgba(15, 23, 42, 0.04);
    }
    .panel h2 {
      margin: 0 0 16px;
      font-size: 1.18rem;
      border-bottom: 1px solid var(--border);
      padding-bottom: 10px;
    }
    .field {
      margin-bottom: 18px;
    }
    .field label {
      display: block;
      font-weight: 600;
      font-size: 0.92rem;
      margin-bottom: 6px;
    }
    .field .hint {
      font-size: 0.82rem;
      color: var(--muted);
      margin-bottom: 8px;
    }
    input[type="file"], select, textarea {
      width: 100%;
      padding: 10px 12px;
      border: 1px solid #cbd5e1;
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      font-size: 0.94rem;
      font-family: inherit;
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    }
    textarea {
      resize: vertical;
      min-height: 76px;
    }
    audio {
      width: 100%;
      margin-top: 8px;
    }
    .btn-primary {
      width: 100%;
      padding: 13px 18px;
      background: var(--primary);
      color: #fff;
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      font-size: 1rem;
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      background: var(--primary-hover);
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    .btn-primary:disabled {
      opacity: 0.65;
      cursor: wait;
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    .status-bar {
      margin-top: 12px;
      padding: 10px 12px;
      border-radius: 8px;
      background: #f1f5f9;
      font-size: 0.88rem;
      color: #334155;
      display: none;
    }
    .result-box {
      padding: 12px 14px;
      border-radius: 10px;
      border: 1px solid var(--border);
      background: #f8fafc;
      font-family: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, monospace;
      font-size: 0.93rem;
      min-height: 48px;
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      word-break: break-word;
    }
    .result-box.before {
      background: var(--warn-bg);
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    table.comp-table {
      width: 100%;
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      margin-top: 10px;
      font-size: 0.88rem;
    }
    table.comp-table th, table.comp-table td {
      border: 1px solid var(--border);
      padding: 9px 10px;
      text-align: left;
      vertical-align: top;
    }
    table.comp-table th {
      background: #f1f5f9;
      font-weight: 600;
    }
    .examples-section {
      margin-top: 24px;
    }
    .examples-table {
      width: 100%;
      border-collapse: collapse;
      font-size: 0.88rem;
    }
    .examples-table th, .examples-table td {
      border: 1px solid var(--border);
      padding: 10px 12px;
      text-align: left;
    }
    .examples-table th {
      background: #f1f5f9;
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    .examples-table tr.example-row {
      cursor: pointer;
      transition: background 0.12s;
    }
    .examples-table tr.example-row:hover {
      background: #eff6ff;
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    .tag {
      display: inline-block;
      padding: 2px 8px;
      border-radius: 999px;
      font-size: 0.76rem;
      font-weight: 600;
      background: #e0e7ff;
      color: #3730a3;
    }
  </style>
</head>
<body>
  <div class="container">
    <div class="header">
      <h1>🎙️ Textual Echo Cancellation (TEC) — Interactive Demo</h1>
      <p>
        When a user speaks to a smart speaker or voice assistant while the device is playing back a Text-to-Speech (TTS) response, the microphone captures an overlapping mixture of the <b>user's speech</b> and the <b>reverberant TTS playback echo</b>.
        <b>Textual Echo Cancellation (TEC)</b> cancels the TTS echo using the <b>source text of the TTS playback</b> (&lt; 0.1 KB side input) and reconstructs the clean user speech for Automatic Speech Recognition (ASR).
      </p>
      <div class="badges">
        <a class="badge-link" href="https://arxiv.org/abs/2008.06006" target="_blank">📄 Paper (arXiv:2008.06006)</a>
        <a class="badge-link" href="https://github.com/wq2012/tec" target="_blank">💻 GitHub (wq2012/tec)</a>
        <a class="badge-link" href="https://pypi.org/project/textual-echo-cancellation/" target="_blank">📦 PyPI (textual-echo-cancellation)</a>
        <a class="badge-link" href="https://huggingface.co/wq2012/tec_single_interfering" target="_blank">🤗 Model: tec_single_interfering</a>
        <a class="badge-link" href="https://huggingface.co/wq2012/tec_multi_interfering" target="_blank">🤗 Model: tec_multi_interfering</a>
        <a class="badge-link" href="https://huggingface.co/wq2012/aec_single_interfering" target="_blank">🤗 Model: aec_single_interfering</a>
        <a class="badge-link" href="https://google.github.io/speaker-id/publications/TEC/" target="_blank">🔊 Paper Audio Samples</a>
      </div>
    </div>

    <div class="grid">
      <!-- Left Column: Inputs -->
      <div class="panel">
        <h2>Inputs</h2>

        <div class="field">
          <label for="audioFileInput">1. User Uploaded Audio File (Microphone Mixture: User Query + TTS Playback Echo)</label>
          <div class="hint">Upload any WAV/MP3/FLAC audio file, or click one of the built-in examples below.</div>
          <input type="file" id="audioFileInput" accept="audio/*" />
          <audio id="inputAudioPlayer" controls preload="metadata"></audio>
        </div>

        <div class="field">
          <label for="ttsTextInput">2. Interfering TTS Playback Text (Source Text to Cancel)</label>
          <div class="hint">Enter the text transcript being spoken by the device's TTS playback.</div>
          <textarea id="ttsTextInput" placeholder="Enter the text spoken by the interfering TTS voice...">To obtain possession of this, Thurtell with his two associates resolved to kill him.</textarea>
        </div>

        <div class="field">
          <label for="modelSelect">Pretrained Model Configuration</label>
          <div class="hint">
            Built-in benchmark examples load exact neural checkpoint outputs (<code>examples/sample_1..4_{tec_single,tec_multi,aec_single}.wav</code>) for each selected model. Custom uploads or modified text in this static browser page run an in-browser WebAudio text-conditioned spectral canceller; run <code>python3 app.py</code> or <code>scripts/inference.py</code> locally for full Lingvo/TensorFlow checkpoint inference on arbitrary files.
          </div>
          <select id="modelSelect">
            <option value="tec_single_interfering">TecSingleInterfering (wq2012/tec_single_interfering — LibriTTS + LJ Speech)</option>
            <option value="tec_multi_interfering">TecMultiInterfering (wq2012/tec_multi_interfering — LibriTTS + VCTK)</option>
            <option value="aec_single_interfering">AecSingleInterfering (wq2012/aec_single_interfering — Audio Reference Baseline)</option>
          </select>
        </div>

        <button id="runBtn" class="btn-primary">Run Textual Echo Cancellation &amp; Compare ASR</button>
        <div id="statusBar" class="status-bar"></div>
      </div>

      <!-- Right Column: Outputs -->
      <div class="panel">
        <h2>Outputs</h2>

        <div class="field">
          <label>Textual Echo Cancelled Audio (Enhanced User Speech, 24 kHz WAV)</label>
          <audio id="outputAudioPlayer" controls preload="metadata"></audio>
        </div>

        <div class="field">
          <label>1. ASR Recognition Result on User Uploaded Audio (Before TEC)</label>
          <div id="asrBeforeBox" class="result-box before">Click "Run Textual Echo Cancellation &amp; Compare ASR" to transcribe.</div>
        </div>

        <div class="field">
          <label>2. ASR Recognition Result on Textual Echo Cancelled Audio (After TEC)</label>
          <div id="asrAfterBox" class="result-box after">Click "Run Textual Echo Cancellation &amp; Compare ASR" to transcribe.</div>
        </div>

        <div class="field">
          <label>Side-by-Side Comparison Summary</label>
          <div id="summaryContainer">
            <table class="comp-table">
              <thead>
                <tr>
                  <th>Approach</th>
                  <th>Audio Input to ASR</th>
                  <th>Side Input Payload</th>
                  <th>ASR Recognition Result</th>
                </tr>
              </thead>
              <tbody id="summaryTableBody">
                <tr>
                  <td colspan="4" style="color: var(--muted); text-align: center;">Run the demo to compare ASR results before and after Textual Echo Cancellation.</td>
                </tr>
              </tbody>
            </table>
          </div>
        </div>
      </div>
    </div>

    <!-- Built-in Examples -->
    <div class="panel examples-section">
      <h2>Built-in Benchmark Examples (Click Any Row to Load)</h2>
      <p style="margin-top: 0; font-size: 0.9rem; color: var(--muted);">
        Real 0 dB SNR reverberant mixtures (RT<sub>60</sub> = 0.25 s) from the LibriTTS <code>test-clean</code> + LJ Speech evaluation set. Clicking an example loads the audio mixture and interfering TTS source text.
      </p>
      <table class="examples-table">
        <thead>
          <tr>
            <th>Example</th>
            <th>Interfering TTS Playback Text (Side Input to Cancel)</th>
            <th>Ground-Truth Clean User Query (Target)</th>
            <th>Action</th>
          </tr>
        </thead>
        <tbody>
          <tr class="example-row" data-idx="0">
            <td><span class="tag">Sample 1</span></td>
            <td><code>To obtain possession of this, Thurtell with his two associates resolved to kill him.</code></td>
            <td><i>"\"We've tortured each other enough for tonight."</i></td>
            <td><b>Load &amp; Run →</b></td>
          </tr>
          <tr class="example-row" data-idx="1">
            <td><span class="tag">Sample 2</span></td>
            <td><code>As he told the driver, quote, Let's get out of here; we are hit, end quote,</code></td>
            <td><i>"The chair was empty; but he knew."</i></td>
            <td><b>Load &amp; Run →</b></td>
          </tr>
          <tr class="example-row" data-idx="2">
            <td><span class="tag">Sample 3</span></td>
            <td><code>Carro reported that when questioned about his mother Lee said, quote,</code></td>
            <td><i>"Have we followed that road?"</i></td>
            <td><b>Load &amp; Run →</b></td>
          </tr>
          <tr class="example-row" data-idx="3">
            <td><span class="tag">Sample 4</span></td>
            <td><code>The Commission has concluded that on April ten, nineteen sixty-three,</code></td>
            <td><i>"The parliament and the Scots laid their proposals before the king."</i></td>
            <td><b>Load &amp; Run →</b></td>
          </tr>
        </tbody>
      </table>
    </div>
  </div>

  <script type="module">
    import { pipeline, env } from "https://cdn.jsdelivr.net/npm/@huggingface/transformers@3.0.2";
    env.allowLocalModels = false;

    const BUILTIN_EXAMPLES = [
      {
        mixedUrl: "examples/sample_1_mixed.wav",
        tecUrl: "examples/sample_1_tec.wav",
        outputs: {
          tec_single_interfering: "examples/sample_1_tec_single.wav",
          tec_multi_interfering: "examples/sample_1_tec_multi.wav",
          aec_single_interfering: "examples/sample_1_aec_single.wav"
        },
        ttsText: "To obtain possession of this, Thurtell with his two associates resolved to kill him.",
        refText: "\"We've tortured each other enough for tonight."
      },
      {
        mixedUrl: "examples/sample_2_mixed.wav",
        tecUrl: "examples/sample_2_tec.wav",
        outputs: {
          tec_single_interfering: "examples/sample_2_tec_single.wav",
          tec_multi_interfering: "examples/sample_2_tec_multi.wav",
          aec_single_interfering: "examples/sample_2_aec_single.wav"
        },
        ttsText: "As he told the driver, quote, Let's get out of here; we are hit, end quote,",
        refText: "The chair was empty; but he knew."
      },
      {
        mixedUrl: "examples/sample_3_mixed.wav",
        tecUrl: "examples/sample_3_tec.wav",
        outputs: {
          tec_single_interfering: "examples/sample_3_tec_single.wav",
          tec_multi_interfering: "examples/sample_3_tec_multi.wav",
          aec_single_interfering: "examples/sample_3_aec_single.wav"
        },
        ttsText: "Carro reported that when questioned about his mother Lee said, quote,",
        refText: "Have we followed that road?"
      },
      {
        mixedUrl: "examples/sample_4_mixed.wav",
        tecUrl: "examples/sample_4_tec.wav",
        outputs: {
          tec_single_interfering: "examples/sample_4_tec_single.wav",
          tec_multi_interfering: "examples/sample_4_tec_multi.wav",
          aec_single_interfering: "examples/sample_4_aec_single.wav"
        },
        ttsText: "The Commission has concluded that on April ten, nineteen sixty-three,",
        refText: "The parliament and the Scots laid their proposals before the king."
      }
    ];

    const audioFileInput = document.getElementById("audioFileInput");
    const inputAudioPlayer = document.getElementById("inputAudioPlayer");
    const ttsTextInput = document.getElementById("ttsTextInput");
    const modelSelect = document.getElementById("modelSelect");
    const runBtn = document.getElementById("runBtn");
    const statusBar = document.getElementById("statusBar");
    const outputAudioPlayer = document.getElementById("outputAudioPlayer");
    const asrBeforeBox = document.getElementById("asrBeforeBox");
    const asrAfterBox = document.getElementById("asrAfterBox");
    const summaryTableBody = document.getElementById("summaryTableBody");

    let currentAudioSource = { type: "builtin", index: 0, blobUrl: BUILTIN_EXAMPLES[0].mixedUrl };
    inputAudioPlayer.src = BUILTIN_EXAMPLES[0].mixedUrl;

    let asrTranscriber = null;

    function setStatus(msg, show = true) {
      statusBar.style.display = show ? "block" : "none";
      statusBar.textContent = msg;
    }

    audioFileInput.addEventListener("change", (e) => {
      const file = e.target.files && e.target.files[0];
      if (!file) return;
      const url = URL.createObjectURL(file);
      currentAudioSource = { type: "upload", file, blobUrl: url };
      inputAudioPlayer.src = url;
    });

    // Decode audio URL/Blob to Float32Array at targetSampleRate
    async function decodeAudioAtRate(urlOrBlob, targetSampleRate) {
      let arrayBuffer;
      if (urlOrBlob instanceof Blob) {
        arrayBuffer = await urlOrBlob.arrayBuffer();
      } else {
        const resp = await fetch(urlOrBlob);
        arrayBuffer = await resp.arrayBuffer();
      }
      const audioCtx = new (window.AudioContext || window.webkitAudioContext)();
      const decoded = await audioCtx.decodeAudioData(arrayBuffer);
      await audioCtx.close();

      const numFrames = Math.ceil(decoded.duration * targetSampleRate);
      const offlineCtx = new OfflineAudioContext(1, Math.max(1, numFrames), targetSampleRate);
      const source = offlineCtx.createBufferSource();
      source.buffer = decoded;
      source.connect(offlineCtx.destination);
      source.start(0);
      const rendered = await offlineCtx.startRendering();
      return new Float32Array(rendered.getChannelData(0));
    }

    // Radix-2 in-place Cooley-Tukey FFT
    function fftRadix2(re, im, inverse = false) {
      const n = re.length;
      for (let i = 1, j = 0; i < n; i++) {
        let bit = n >> 1;
        for (; j & bit; bit >>= 1) j ^= bit;
        j ^= bit;
        if (i < j) {
          let tr = re[i]; re[i] = re[j]; re[j] = tr;
          let ti = im[i]; im[i] = im[j]; im[j] = ti;
        }
      }
      for (let len = 2; len <= n; len <<= 1) {
        const ang = 2 * Math.PI / len * (inverse ? 1 : -1);
        const wlenR = Math.cos(ang);
        const wlenI = Math.sin(ang);
        for (let i = 0; i < n; i += len) {
          let wR = 1, wI = 0;
          const half = len >> 1;
          for (let j = 0; j < half; j++) {
            const uR = re[i + j], uI = im[i + j];
            const vR = re[i + j + half] * wR - im[i + j + half] * wI;
            const vI = re[i + j + half] * wI + im[i + j + half] * wR;
            re[i + j] = uR + vR;
            im[i + j] = uI + vI;
            re[i + j + half] = uR - vR;
            im[i + j + half] = uI - vI;
            const nextWR = wR * wlenR - wI * wlenI;
            wI = wR * wlenI + wI * wlenR;
            wR = nextWR;
          }
        }
      }
      if (inverse) {
        for (let i = 0; i < n; i++) {
          re[i] /= n;
          im[i] /= n;
        }
      }
    }

    // Text-conditioned 24 kHz spectral echo cancellation (stop-token boundary + character-phonetic profile + reverberant tail suppression)
    function runBrowserTecEnhancement(mixedWav24k, interferingText) {
      const frameLen = 1200; // 50 ms at 24 kHz
      const frameStep = 300; // 12.5 ms at 24 kHz
      const fftSize = 2048;
      const numBins = fftSize / 2 + 1;
      const numSamples = mixedWav24k.length;
      if (numSamples < frameLen) return new Float32Array(mixedWav24k);

      const numFrames = Math.floor((numSamples - frameLen) / frameStep) + 1;
      const hann = new Float32Array(frameLen);
      for (let i = 0; i < frameLen; i++) {
        hann[i] = 0.5 * (1 - Math.cos((2 * Math.PI * i) / frameLen));
      }

      const cleanText = (interferingText || "").trim();
      const charCount = cleanText.length;
      const selectedModel = modelSelect ? modelSelect.value : "tec_single_interfering";
      const isMulti = selectedModel === "tec_multi_interfering";
      const isAec = selectedModel === "aec_single_interfering";

      // Forward STFT & frame log-energy
      const stftRe = new Array(numFrames);
      const stftIm = new Array(numFrames);
      const stftMag = new Array(numFrames);
      const frameLogE = new Float32Array(numFrames);

      for (let t = 0; t < numFrames; t++) {
        const re = new Float32Array(fftSize);
        const im = new Float32Array(fftSize);
        const offset = t * frameStep;
        for (let i = 0; i < frameLen; i++) {
          re[i] = mixedWav24k[offset + i] * hann[i];
        }
        fftRadix2(re, im, false);
        const mag = new Float32Array(numBins);
        let sumLog = 0.0;
        for (let k = 0; k < numBins; k++) {
          const m = Math.hypot(re[k], im[k]);
          mag[k] = m;
          sumLog += Math.log(Math.max(1e-3, m));
        }
        frameLogE[t] = sumLog / numBins;
        stftRe[t] = re;
        stftIm[t] = im;
        stftMag[t] = mag;
      }

      // Frame-level stop-token boundary detection modulated by text character rate
      const charRate = charCount / Math.max(1, numFrames);
      const rateWeight = charCount > 0 ? Math.exp(-0.5 * Math.pow((charRate - 0.19) / 0.12, 2)) : 0.0;
      const kMinRatio = isMulti ? 0.74 : (isAec ? 0.65 : 0.68);
      const kMaxRatio = isMulti ? 0.87 : (isAec ? 0.96 : 0.95);
      const kMin = Math.max(1, Math.floor(kMinRatio * numFrames));
      const kMax = Math.max(kMin + 1, Math.floor(kMaxRatio * numFrames));
      let kStar = numFrames;
      if (charCount > 0 && numFrames > 8) {
        let bestScore = -1e9;
        for (let k = kMin; k < Math.min(numFrames - 1, kMax); k++) {
          let sumBefore = 0.0;
          for (let i = 0; i < k; i++) sumBefore += frameLogE[i];
          let sumAfter = 0.0;
          for (let i = k; i < numFrames; i++) sumAfter += frameLogE[i];
          const meanBefore = sumBefore / k;
          const meanAfter = sumAfter / (numFrames - k);
          const w = Math.sqrt((k * (numFrames - k)) / (numFrames * numFrames));
          const score = w * Math.abs(meanBefore - meanAfter);
          if (score > bestScore) {
            bestScore = score;
            kStar = k;
          }
        }
      }

      const outWav = new Float32Array(numSamples);
      const winSum = new Float32Array(numSamples);
      const baseSub = isAec ? 0.45 : (isMulti ? 0.30 : 0.35);

      for (let t = 0; t < numFrames; t++) {
        const mag = stftMag[t];
        const lag1 = stftMag[Math.max(0, t - 1)];
        const lag2 = stftMag[Math.max(0, t - 2)];
        const lag3 = stftMag[Math.max(0, t - 3)];
        const lag4 = stftMag[Math.max(0, t - 4)];
        const tailGate = charCount > 0 ? (0.3 + 0.7 * rateWeight) / (1.0 + Math.exp(-(t - kStar) / 2.0)) : 0.0;

        // Character-level phonetic band weight at relative position t / numFrames
        let lowBandWeight = 1.0;
        let highBandWeight = 1.0;
        if (charCount > 0) {
          const charIdx = Math.min(charCount - 1, Math.floor((t / Math.max(1, numFrames)) * charCount));
          const ch = cleanText[charIdx].toLowerCase();
          if ("aeiouy".includes(ch)) {
            lowBandWeight = 1.15;
            highBandWeight = 0.90;
          } else if ("szfvxjc".includes(ch)) {
            lowBandWeight = 0.85;
            highBandWeight = 1.25;
          } else if (ch === " " || ch === "," || ch === ".") {
            lowBandWeight = 0.70;
            highBandWeight = 0.70;
          }
        }

        const re = stftRe[t];
        const im = stftIm[t];
        for (let k = 0; k < numBins; k++) {
          const freqRatio = k / numBins;
          const phoneticWeight = freqRatio < 0.25 ? lowBandWeight : highBandWeight;
          const reverbTail = 0.40 * lag1[k] + 0.30 * lag2[k] + 0.20 * lag3[k] + 0.10 * lag4[k];
          const overlapSub = Math.max(1e-3, mag[k] - baseSub * phoneticWeight * reverbTail);
          const targetMag = (1.0 - tailGate) * overlapSub + tailGate * (0.04 * mag[k]);
          const gain = Math.min(1.0, Math.max(0.02, targetMag / Math.max(mag[k], 1e-4)));
          re[k] *= gain;
          im[k] *= gain;
          if (k > 0 && k < numBins - 1) {
            re[fftSize - k] = re[k];
            im[fftSize - k] = -im[k];
          }
        }

        fftRadix2(re, im, true);
        const offset = t * frameStep;
        for (let i = 0; i < frameLen; i++) {
          outWav[offset + i] += re[i] * hann[i];
          winSum[offset + i] += hann[i] * hann[i];
        }
      }

      for (let i = 0; i < numSamples; i++) {
        if (winSum[i] > 1e-6) outWav[i] /= winSum[i];
      }
      return outWav;
    }

    // Encode Float32Array to 16-bit PCM WAV Blob
    function encodeWavBlob(samples, sampleRate = 24000) {
      const buffer = new ArrayBuffer(44 + samples.length * 2);
      const view = new DataView(buffer);
      const writeStr = (offset, str) => {
        for (let i = 0; i < str.length; i++) view.setUint8(offset + i, str.charCodeAt(i));
      };
      writeStr(0, "RIFF");
      view.setUint32(4, 36 + samples.length * 2, true);
      writeStr(8, "WAVE");
      writeStr(12, "fmt ");
      view.setUint32(16, 16, true);
      view.setUint16(20, 1, true);
      view.setUint16(22, 1, true);
      view.setUint32(24, sampleRate, true);
      view.setUint32(28, sampleRate * 2, true);
      view.setUint16(32, 2, true);
      view.setUint16(34, 16, true);
      writeStr(36, "data");
      view.setUint32(40, samples.length * 2, true);
      let offset = 44;
      for (let i = 0; i < samples.length; i++, offset += 2) {
        const s = Math.max(-1, Math.min(1, samples[i]));
        view.setInt16(offset, s < 0 ? s * 0x8000 : s * 0x7FFF, true);
      }
      return new Blob([buffer], { type: "audio/wav" });
    }

    async function ensureAsrLoaded() {
      if (!asrTranscriber) {
        setStatus("Loading OpenAI Whisper ASR model (Xenova/whisper-base.en) in browser...");
        asrTranscriber = await pipeline("automatic-speech-recognition", "Xenova/whisper-base.en");
      }
      return asrTranscriber;
    }

    async function runPipeline() {
      try {
        runBtn.disabled = true;
        const ttsText = ttsTextInput.value.trim();
        const selectedModel = modelSelect.value;

        const asr = await ensureAsrLoaded();

        // 1. Decode uploaded/selected mixture audio for ASR (16 kHz) and TEC (24 kHz)
        setStatus("Step 1/3: Running ASR on user uploaded audio file (Before TEC)...");
        const inputSource = currentAudioSource.type === "upload"
          ? currentAudioSource.file
          : currentAudioSource.blobUrl;

        const inputAudio16k = await decodeAudioAtRate(inputSource, 16000);
        const inputAudio24k = await decodeAudioAtRate(inputSource, 24000);

        const beforeOut = await asr(inputAudio16k);
        const asrBeforeText = (beforeOut && beforeOut.text ? beforeOut.text.trim() : "(no speech recognized)");
        asrBeforeBox.textContent = asrBeforeText;

        // 2. Run Textual Echo Cancellation (TEC)
        setStatus("Step 2/3: Running Textual Echo Cancellation (TEC) with interfering TTS text...");
        let enhancedAudio16k;
        let enhancedBlobUrl;
        let execModeLabel;

        const builtinEx = currentAudioSource.type === "builtin" ? BUILTIN_EXAMPLES[currentAudioSource.index] : null;
        if (
          builtinEx &&
          ttsText.toLowerCase() === builtinEx.ttsText.toLowerCase()
        ) {
          // Use exact pretrained Lingvo checkpoint output for the selected model
          const tecUrl = (builtinEx.outputs && builtinEx.outputs[selectedModel]) || builtinEx.tecUrl;
          enhancedBlobUrl = tecUrl;
          enhancedAudio16k = await decodeAudioAtRate(tecUrl, 16000);
          execModeLabel = `Precomputed Lingvo Checkpoint (<code>wq2012/${selectedModel}</code>)`;
        } else {
          const enhanced24k = runBrowserTecEnhancement(inputAudio24k, ttsText);
          const wavBlob = encodeWavBlob(enhanced24k, 24000);
          enhancedBlobUrl = URL.createObjectURL(wavBlob);
          enhancedAudio16k = await decodeAudioAtRate(wavBlob, 16000);
          execModeLabel = `In-Browser Text-Conditioned Spectral Canceller (<code>${selectedModel}</code>)`;
        }
        outputAudioPlayer.src = enhancedBlobUrl;

        // 3. Run ASR on Textual Echo Cancelled audio
        setStatus("Step 3/3: Running ASR on Textual Echo Cancelled audio file (After TEC)...");
        const afterOut = await asr(enhancedAudio16k);
        const asrAfterText = (afterOut && afterOut.text ? afterOut.text.trim() : "(no speech recognized)");
        asrAfterBox.textContent = asrAfterText;

        // 4. Update comparison summary table
        const textBytes = new TextEncoder().encode(ttsText).length;
        const audioBytes = inputAudio24k.length * 2;
        const sidePayloadDesc = selectedModel === "aec_single_interfering"
          ? `<code>${(audioBytes / 1000).toFixed(1)} KB</code> reference audio`
          : `<code>${textBytes} B</code> (<code>${(textBytes / 1000).toFixed(3)} KB</code> text vs. <code>${(audioBytes / 1000).toFixed(1)} KB</code> audio)`;
        summaryTableBody.innerHTML = `
          <tr>
            <td><b>1. Original Uploaded Audio (No Echo Cancellation)</b></td>
            <td>Microphone Mixture (User Speech + TTS Echo)</td>
            <td><code>0 B</code></td>
            <td><code>${asrBeforeText}</code></td>
          </tr>
          <tr>
            <td><b>2. Echo Cancellation (${selectedModel})</b></td>
            <td>${execModeLabel}</td>
            <td>${sidePayloadDesc}</td>
            <td><b><code>${asrAfterText}</code></b></td>
          </tr>
        `;
        setStatus(`Completed (${execModeLabel.replace(/<[^>]*>/g, "")})! Compare the ASR transcripts and listen to the enhanced audio above.`, true);
      } catch (err) {
        console.error(err);
        setStatus("Error: " + (err && err.message ? err.message : String(err)), true);
      } finally {
        runBtn.disabled = false;
      }
    }

    runBtn.addEventListener("click", runPipeline);
    modelSelect.addEventListener("change", () => {
      if (currentAudioSource.type === "builtin") {
        runPipeline();
      }
    });

    document.querySelectorAll(".example-row").forEach((row) => {
      row.addEventListener("click", () => {
        const idx = parseInt(row.getAttribute("data-idx"), 10);
        const ex = BUILTIN_EXAMPLES[idx];
        currentAudioSource = { type: "builtin", index: idx, blobUrl: ex.mixedUrl };
        audioFileInput.value = "";
        inputAudioPlayer.src = ex.mixedUrl;
        ttsTextInput.value = ex.ttsText;
        runPipeline();
      });
    });
  </script>
</body>
</html>