[Refactor] improve the JS example

samples/js/live-audio-transcription-example/app.js

@@ -0,0 +1,189 @@
+// Live Audio Transcription Example — Foundry Local JS SDK
+//
+// Demonstrates real-time microphone-to-text using the JS SDK.
+// Requires: npm install foundry-local-sdk naudiodon2
+//
+// Usage: node app.js
+
+import { FoundryLocalManager } from 'foundry-local-sdk';
+
+console.log('╔══════════════════════════════════════════════════════════╗');
+console.log('║   Foundry Local — Live Audio Transcription (JS SDK)     ║');
+console.log('╚══════════════════════════════════════════════════════════╝');
+console.log();
+
+// Initialize the Foundry Local SDK
+console.log('Initializing Foundry Local SDK...');
+const manager = FoundryLocalManager.create({
+    appName: 'foundry_local_live_audio',
+    logLevel: 'info'
+});
+console.log('✓ SDK initialized');
+
+// Get and load the nemotron model
+const modelAlias = 'nemotron';
+let model = await manager.catalog.getModel(modelAlias);
+if (!model) {
+    console.error(`ERROR: Model "${modelAlias}" not found in catalog.`);
+    process.exit(1);
+}
+
+console.log(`Found model: ${model.id}`);
+console.log('Downloading model (if needed)...');
+await model.download((progress) => {
+    process.stdout.write(`\rDownloading... ${progress.toFixed(2)}%`);
+});
+console.log('\n✓ Model downloaded');
+
+console.log('Loading model...');
+await model.load();
+console.log('✓ Model loaded');
+
+// Create live transcription session (same pattern as C# sample).
+const audioClient = model.createAudioClient();
+const session = audioClient.createLiveTranscriptionSession();
+
+session.settings.sampleRate = 16000;  // Default is 16000; shown here for clarity
+session.settings.channels = 1;
+session.settings.bitsPerSample = 16;
+session.settings.language = 'en';
+
+console.log('Starting streaming session...');
+await session.start();
+console.log('✓ Session started');
+
+// Read transcription results in background
+const readPromise = (async () => {
+    try {
+        for await (const result of session.getTranscriptionStream()) {
+            const text = result.content?.[0]?.text;
+            if (!text) continue;
+
+            // `is_final` is a transcript-state marker only. It should not stop the app.
+            if (result.is_final) {
+                process.stdout.write(`\n  [FINAL] ${text}\n`);
+            } else {
+                process.stdout.write(text);
+            }
+        }
+    } catch (err) {
+        if (err.name !== 'AbortError') {
+            console.error('Stream error:', err.message);
+        }
+    }
+})();
+
+// --- Microphone capture ---
+// This example uses naudiodon2 for cross-platform audio capture.
+// Install with: npm install naudiodon2
+//
+// If you prefer a different audio library, just push PCM bytes
+// (16-bit signed LE, mono, 16kHz) via session.append().
+
+let audioInput;
+try {
+    const { default: portAudio } = await import('naudiodon2');
+
+    audioInput = portAudio.AudioIO({
+        inOptions: {
+            channelCount: session.settings.channels,
+            sampleFormat: session.settings.bitsPerSample === 16
+                ? portAudio.SampleFormat16Bit
+                : portAudio.SampleFormat32Bit,
+            sampleRate: session.settings.sampleRate,
+            // Larger chunk size lowers callback frequency and reduces overflow risk.
+            framesPerBuffer: 3200,
+            // Allow deeper native queue during occasional event-loop stalls.
+            maxQueue: 64
+        }
+    });
+
+    const appendQueue = [];
+    let pumping = false;
+    let warnedQueueDrop = false;
+
+    const pumpAudio = async () => {
+        if (pumping) return;
+        pumping = true;
+        try {
+            while (appendQueue.length > 0) {
+                const pcm = appendQueue.shift();
+                await session.append(pcm);
+            }
+        } catch (err) {
+            console.error('append error:', err.message);
+        } finally {
+            pumping = false;
+            // Handle race where new data arrived after loop exit.
+            if (appendQueue.length > 0) {
+                void pumpAudio();
+            }
+        }
+    };
+
+    audioInput.on('data', (buffer) => {
+        // Single copy: slice the underlying ArrayBuffer to get an independent Uint8Array.
+        const copy = new Uint8Array(buffer.buffer, buffer.byteOffset, buffer.byteLength).slice();
+
+        // Keep a bounded queue to avoid unbounded memory growth.
+        if (appendQueue.length >= 100) {
+            appendQueue.shift();
+            if (!warnedQueueDrop) {
+                warnedQueueDrop = true;
+                console.warn('Audio append queue overflow; dropping oldest chunk to keep stream alive.');
+            }
+        }
+
+        appendQueue.push(copy);
+        void pumpAudio();
+    });
+
+    console.log();
+    console.log('════════════════════════════════════════════════════════════');
+    console.log('  LIVE TRANSCRIPTION ACTIVE');
+    console.log('  Speak into your microphone.');
+    console.log('  Press Ctrl+C to stop.');
+    console.log('════════════════════════════════════════════════════════════');
+    console.log();
+
+    audioInput.start();
+} catch (err) {
+    console.warn('⚠ Could not initialize microphone (naudiodon2 may not be installed).');
+    console.warn('  Install with: npm install naudiodon2');
+    console.warn('  Falling back to synthetic audio test...');
+    console.warn();
+
+    // Fallback: push 2 seconds of synthetic PCM (440Hz sine wave)
+    const sampleRate = session.settings.sampleRate;
+    const duration = 2;
+    const totalSamples = sampleRate * duration;
+    const pcmBytes = new Uint8Array(totalSamples * 2);
+    for (let i = 0; i < totalSamples; i++) {
+        const t = i / sampleRate;
+        const sample = Math.round(32767 * 0.5 * Math.sin(2 * Math.PI * 440 * t));
+        pcmBytes[i * 2] = sample & 0xFF;
+        pcmBytes[i * 2 + 1] = (sample >> 8) & 0xFF;
+    }
+
+    // Push in 100ms chunks
+    const chunkSize = (sampleRate / 10) * 2;
+    for (let offset = 0; offset < pcmBytes.length; offset += chunkSize) {
+        const len = Math.min(chunkSize, pcmBytes.length - offset);
+        await session.append(pcmBytes.slice(offset, offset + len));
+    }
+
+    console.log('✓ Synthetic audio pushed');
+}
+
+// Handle graceful shutdown
+process.on('SIGINT', async () => {
+    console.log('\n\nStopping...');
+    if (audioInput) {
+        audioInput.quit();
+    }
+    await session.stop();
+    await readPromise;
+    await model.unload();
+    console.log('✓ Done');
+    process.exit(0);
+});