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pages-ai-voice-chat

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End-to-end voice pipeline example: Browser 48kHz capture → AudioWorklet resampling/framing → WebSocket streaming → PagesAI ASR → stable text triggers PagesAI TTS → downstream PCM playback. Designed for deployment on EdgeOne Pages (Node Functions).

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# EdgeOne Pages AI Voice Chat

End-to-end voice pipeline example: Browser 48kHz capture → AudioWorklet resampling/framing → WebSocket streaming → PagesAI ASR → stable text triggers PagesAI TTS → downstream PCM playback. Designed for deployment on EdgeOne Pages (Node Functions).

## Deploy

[![Deploy with EdgeOne Pages](https://cdnstatic.tencentcs.com/edgeone/pages/deploy.svg)](https://edgeone.ai/pages/new?template=pages-ai-voice-chat)

Live Demo: https://pages-ai-voice-chat.edgeone.site

More Templates: [EdgeOne Pages](https://pages.edgeone.ai/templates)

## Project Positioning

- An open-source template ready for EdgeOne Pages (Node Functions), delivering a browser-to-backend real-time voice loop out of the box.
- Aims to cut boilerplate for voice apps, demo WebSocket + audio best practices, and quickly extend to CS/chatbot/assistant scenarios.

## Features

- **48 kHz microphone capture** with linear downsampling to 16 kHz via AudioWorklet, pushed in fixed 40 ms frames to reduce WebSocket frame count.
- **Voice Activity Detection (VAD)**: Dual-window detection mechanism (200ms interrupt sensitivity, 400ms stability window) automatically interrupts TTS playback when user speaks.
- **Adaptive Noise Reduction**: Real-time noise floor estimation, spectral subtraction, and soft noise gating for cleaner audio input.
- **Bidirectional WebSocket protocol**: `start/audio/interrupt/interrupt_tts/heartbeat` requests, `ready/asr_ready/transcript/ai_text` and binary audio responses.
- **PagesAI pipeline**: ASR WebSocket for real-time transcription; stable text is chained with PagesAI TTS, server resamples to client sample rate before downstream transmission.
- **LLM-generated replies**: Stable transcription text is sent to a large model service, then synthesized via TTS, forming a hear-think-reply loop.
- **Intelligent playback scheduling**: Pre-scheduled audio buffering with batch scheduling to eliminate playback gaps and enable smooth interruption.
- **Auto-reconnection**: Exponential backoff reconnection strategy (max 10s delay) with silent recovery to maintain seamless user experience.
- **Real-time UI**: Client maintains Float32 playback queue, keepalive heartbeat, live transcription panel with timing metadata.

## Architecture

Flow: Browser AudioWorklet produces 16 kHz/40 ms PCM → WebSocket `/websocket` → Server establishes ASR session and forwards audio → ASR callback transcription → final segment triggers TTS SSE → Server resamples TTS audio and sends binary downstream → Client queue playback.

![](https://cdnstatic.tencentcs.com/edgeone/pages/assets/sF3Jp-1764770699982.png)

## Directory Structure

```
.
├── index.html                 # UI, static entry point
├── client.js                  # Frontend logic: capture, WS protocol, playback queue and UI
├── audio-processor.js         # AudioWorklet: 48k -> 16k, 40ms framing
├── node-functions/
│   ├── websocket.ts           # Main WS handler: ASR forwarding + LLM + TTS chain
│   ├── asr/                   # ASR WebSocket wrapper
│   ├── tts/                   # TTS wrapper and resampling
│   ├── types/                 # PagesAI runtime type declarations
│   └── utils/                 # WS helpers and audio utilities
```

## Running and Deployment

### Runtime Requirements

- Node 18+ (EdgeOne Pages Node Functions default), with built-in `Buffer/crypto/ws`.
- Browser with AudioWorklet and `getUserMedia` support.

## Environment Variables

### PAGES_AI runtime (required)

- `PAGES_API_TOKEN`: issued `api_token`. You can obtain your API Token from:
  - [EdgeOne Pages API Token documentation](https://pages.edgeone.ai/document/api-token)

### Global Object

- `PagesAI: new ({ apiToken }) => PagesAIShape`
  - `asr: AsrBinding`
  - `llm: LlmBinding`
  - `tts: TtsBinding`

> Provide this environment variable before usage:
>
> - `PAGES_API_TOKEN`: issued `api_token`. Get your API Token from [EdgeOne Pages API Token documentation](https://pages.edgeone.ai/document/api-token)
>   Access it from `context.env` inside Node Functions handlers.

### ASR (streaming speech recognition)

```ts
interface AsrBinding {
  createSocket(): Promise<{
    socket: WebSocket; // signed WS connection, ready to send()
    engineModelType: string;
    voiceId: string;
  }>;
}
```

Usage example (token comes from `context.env` in your handler):

```ts
// context is provided by the Node Functions runtime
const ai = new PagesAI({ apiToken: context.env.PAGES_API_TOKEN! });
const { socket } = await ai.asr.createSocket();

// send audio binary (PCM/Buffer)
socket.send(pcmBuffer);

// listen to recognition result
socket.on('message', (data) => {
  try {
    const msg = JSON.parse(data.toString());
    if (msg.type === 'transcript') {
      // msg.text, msg.isFinal, etc.
      console.log('ASR transcript:', msg.text, msg.isFinal);
    }
  } catch {
    // ignore non-JSON
  }
});

// end stream
socket.send(JSON.stringify({ type: 'end' }));
```

### LLM (chat completion)

```ts
type ChatMessage = { role: 'system' | 'user' | 'assistant'; content: string };

interface LlmBinding {
  complete(messages: ChatMessage[]): Promise<string>;
}
```

Usage example (token from `context.env`):

```ts
const messages = [
  { role: 'system', content: 'You are a concise assistant' },
  { role: 'user', content: 'Hello' },
];
const ai = new PagesAI({ apiToken: context.env.PAGES_API_TOKEN! });
const answer: string = await ai.llm.complete(messages);
// answer: "Hello!"
```

### TTS (text-to-speech)

```ts
interface TtsSynthesizeOptions {
  signal?: AbortSignal;
}

interface TtsBinding {
  synthesize(
    text: string,
    options?: TtsSynthesizeOptions
  ): Promise<Array<{ data: string }>>;
}
```

Usage example (token from `context.env`):

```ts
const ai = new PagesAI({ apiToken: context.env.PAGES_API_TOKEN! });
const events = await ai.tts.synthesize('Hello');
for (const e of events) {
  // e.data is SSE data string; parse manually (see tts/utils.ts)
}
```

## Audio and Pipeline Parameters

### Capture Configuration
- **Sample Rate**: 48 kHz native capture, downsampled to 16 kHz
- **Format**: Mono, Float32 → Int16 PCM conversion
- **Frame Size**: 40 ms fixed chunks (640 samples @ 16 kHz)
- **Browser Features**: Echo cancellation, noise suppression, auto gain control enabled

### VAD & Noise Reduction
- **VAD Threshold**: 0.01 (configurable volume threshold)
- **Interrupt Sensitivity**: 200 ms window for fast user speech detection
- **Stability Window**: 400 ms window for voice end detection
- **Noise Gate**: 0.005 threshold with adaptive noise floor estimation
- **Noise Estimation**: 500 ms sample window using 10th percentile

### Streaming
- **Upstream**: 16 kHz Int16 PCM, 40 ms fixed frames via WebSocket binary
- **Downstream**: TTS defaults to 24 kHz PCM, server linearly resamples to client sample rate (16 kHz) before sending as Float32
- **Heartbeat**: 5000 ms interval with auto-reconnect on connection loss
- **Reconnection**: Exponential backoff with 1s, 2s, 4s, 8s, 10s (max) delays

## Extensibility

- Swap/configure LLM: `node-functions/websocket.ts` uses PagesAI `llm.complete`; replace the model, system prompts, or memory strategy as needed.
- Observability & debugging: Pages console provides real-time server logs for `node-functions` (connections, ASR/TTS failures) to help troubleshooting.

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