@azure/ai-voicelive (JavaScript/TypeScript)

Real-time voice AI SDK for building bidirectional voice assistants with Azure AI in Node.js and browser environments.

Installation

npm install @azure/ai-voicelive @azure/identity
# TypeScript users
npm install @types/node

Current Version: 1.0.0-beta.3

Supported Environments:

• Node.js LTS versions (20+)
• Modern browsers (Chrome, Firefox, Safari, Edge)

Environment Variables

AZURE_VOICELIVE_ENDPOINT=https://<resource>.cognitiveservices.azure.com
# Optional: API key if not using Entra ID
AZURE_VOICELIVE_API_KEY=<your-api-key>
# Optional: Logging
AZURE_LOG_LEVEL=info
AZURE_TOKEN_CREDENTIALS=prod # Required only if DefaultAzureCredential is used in production

Authentication

Microsoft Entra Token Credential (Recommended)

import { DefaultAzureCredential, ManagedIdentityCredential } from "@azure/identity";
import { VoiceLiveClient } from "@azure/ai-voicelive";

// Local dev: DefaultAzureCredential. Production: set AZURE_TOKEN_CREDENTIALS=prod or AZURE_TOKEN_CREDENTIALS=<specific_credential>
const credential = new DefaultAzureCredential({requiredEnvVars: ["AZURE_TOKEN_CREDENTIALS"]});
// Or use a specific credential directly in production:
// See https://learn.microsoft.com/javascript/api/overview/azure/identity-readme?view=azure-node-latest#credential-classes
// const credential = new ManagedIdentityCredential();
const endpoint = "https://your-resource.cognitiveservices.azure.com";

const client = new VoiceLiveClient(endpoint, credential);

API Key

import { AzureKeyCredential } from "@azure/core-auth";
import { VoiceLiveClient } from "@azure/ai-voicelive";

const endpoint = "https://your-resource.cognitiveservices.azure.com";
const credential = new AzureKeyCredential("your-api-key");

const client = new VoiceLiveClient(endpoint, credential);

Client Hierarchy

VoiceLiveClient
└── VoiceLiveSession (WebSocket connection)
    ├── updateSession()      → Configure session options
    ├── subscribe()          → Event handlers (Azure SDK pattern)
    ├── sendAudio()          → Stream audio input
    ├── addConversationItem() → Add messages/function outputs
    └── sendEvent()          → Send raw protocol events

Quick Start

import { DefaultAzureCredential } from "@azure/identity";
import { VoiceLiveClient } from "@azure/ai-voicelive";

const credential = new DefaultAzureCredential({requiredEnvVars: ["AZURE_TOKEN_CREDENTIALS"]});
const endpoint = process.env.AZURE_VOICELIVE_ENDPOINT!;

// Create client and start session
const client = new VoiceLiveClient(endpoint, credential);
const session = await client.startSession("gpt-4o-mini-realtime-preview");

// Configure session
await session.updateSession({
  modalities: ["text", "audio"],
  instructions: "You are a helpful AI assistant. Respond naturally.",
  voice: {
    type: "azure-standard",
    name: "en-US-AvaNeural",
  },
  turnDetection: {
    type: "server_vad",
    threshold: 0.5,
    prefixPaddingMs: 300,
    silenceDurationMs: 500,
  },
  inputAudioFormat: "pcm16",
  outputAudioFormat: "pcm16",
});

// Subscribe to events
const subscription = session.subscribe({
  onResponseAudioDelta: async (event, context) => {
    // Handle streaming audio output
    const audioData = event.delta;
    playAudioChunk(audioData);
  },
  onResponseTextDelta: async (event, context) => {
    // Handle streaming text
    process.stdout.write(event.delta);
  },
  onInputAudioTranscriptionCompleted: async (event, context) => {
    console.log("User said:", event.transcript);
  },
});

// Send audio from microphone
function sendAudioChunk(audioBuffer: ArrayBuffer) {
  session.sendAudio(audioBuffer);
}

Session Configuration

await session.updateSession({
  // Modalities
  modalities: ["audio", "text"],
  
  // System instructions
  instructions: "You are a customer service representative.",
  
  // Voice selection
  voice: {
    type: "azure-standard",  // or "azure-custom", "openai"
    name: "en-US-AvaNeural",
  },
  
  // Turn detection (VAD)
  turnDetection: {
    type: "server_vad",      // or "azure_semantic_vad"
    threshold: 0.5,
    prefixPaddingMs: 300,
    silenceDurationMs: 500,
  },
  
  // Audio formats
  inputAudioFormat: "pcm16",
  outputAudioFormat: "pcm16",
  
  // Tools (function calling)
  tools: [
    {
      type: "function",
      name: "get_weather",
      description: "Get current weather",
      parameters: {
        type: "object",
        properties: {
          location: { type: "string" }
        },
        required: ["location"]
      }
    }
  ],
  toolChoice: "auto",
});

Event Handling (Azure SDK Pattern)

The SDK uses a subscription-based event handling pattern:

const subscription = session.subscribe({
  // Connection lifecycle
  onConnected: async (args, context) => {
    console.log("Connected:", args.connectionId);
  },
  onDisconnected: async (args, context) => {
    console.log("Disconnected:", args.code, args.reason);
  },
  onError: async (args, context) => {
    console.error("Error:", args.error.message);
  },
  
  // Session events
  onSessionCreated: async (event, context) => {
    console.log("Session created:", context.sessionId);
  },
  onSessionUpdated: async (event, context) => {
    console.log("Session updated");
  },
  
  // Audio input events (VAD)
  onInputAudioBufferSpeechStarted: async (event, context) => {
    console.log("Speech started at:", event.audioStartMs);
  },
  onInputAudioBufferSpeechStopped: async (event, context) => {
    console.log("Speech stopped at:", event.audioEndMs);
  },
  
  // Transcription events
  onConversationItemInputAudioTranscriptionCompleted: async (event, context) => {
    console.log("User said:", event.transcript);
  },
  onConversationItemInputAudioTranscriptionDelta: async (event, context) => {
    process.stdout.write(event.delta);
  },
  
  // Response events
  onResponseCreated: async (event, context) => {
    console.log("Response started");
  },
  onResponseDone: async (event, context) => {
    console.log("Response complete");
  },
  
  // Streaming text
  onResponseTextDelta: async (event, context) => {
    process.stdout.write(event.delta);
  },
  onResponseTextDone: async (event, context) => {
    console.log("\n--- Text complete ---");
  },
  
  // Streaming audio
  onResponseAudioDelta: async (event, context) => {
    const audioData = event.delta;
    playAudioChunk(audioData);
  },
  onResponseAudioDone: async (event, context) => {
    console.log("Audio complete");
  },
  
  // Audio transcript (what assistant said)
  onResponseAudioTranscriptDelta: async (event, context) => {
    process.stdout.write(event.delta);
  },
  
  // Function calling
  onResponseFunctionCallArgumentsDone: async (event, context) => {
    if (event.name === "get_weather") {
      const args = JSON.parse(event.arguments);
      const result = await getWeather(args.location);
      
      await session.addConversationItem({
        type: "function_call_output",
        callId: event.callId,
        output: JSON.stringify(result),
      });
      
      await session.sendEvent({ type: "response.create" });
    }
  },
  
  // Catch-all for debugging
  onServerEvent: async (event, context) => {
    console.log("Event:", event.type);
  },
});

// Clean up when done
await subscription.close();

Function Calling

// Define tools in session config
await session.updateSession({
  modalities: ["audio", "text"],
  instructions: "Help users with weather information.",
  tools: [
    {
      type: "function",
      name: "get_weather",
      description: "Get current weather for a location",
      parameters: {
        type: "object",
        properties: {
          location: {
            type: "string",
            description: "City and state or country",
          },
        },
        required: ["location"],
      },
    },
  ],
  toolChoice: "auto",
});

// Handle function calls
const subscription = session.subscribe({
  onResponseFunctionCallArgumentsDone: async (event, context) => {
    if (event.name === "get_weather") {
      const args = JSON.parse(event.arguments);
      const weatherData = await fetchWeather(args.location);
      
      // Send function result
      await session.addConversationItem({
        type: "function_call_output",
        callId: event.callId,
        output: JSON.stringify(weatherData),
      });
      
      // Trigger response generation
      await session.sendEvent({ type: "response.create" });
    }
  },
});

Voice Options

Voice Type	Config	Example
Azure Standard	{ type: "azure-standard", name: "..." }	"en-US-AvaNeural"
Azure Custom	{ type: "azure-custom", name: "...", endpointId: "..." }	Custom voice endpoint
Azure Personal	{ type: "azure-personal", speakerProfileId: "..." }	Personal voice clone
OpenAI	{ type: "openai", name: "..." }	"alloy", "echo", "shimmer"

Supported Models

Model	Description	Use Case
gpt-4o-realtime-preview	GPT-4o with real-time audio	High-quality conversational AI
gpt-4o-mini-realtime-preview	Lightweight GPT-4o	Fast, efficient interactions
phi4-mm-realtime	Phi multimodal	Cost-effective applications

Turn Detection Options

// Server VAD (default)
turnDetection: {
  type: "server_vad",
  threshold: 0.5,
  prefixPaddingMs: 300,
  silenceDurationMs: 500,
}

// Azure Semantic VAD (smarter detection)
turnDetection: {
  type: "azure_semantic_vad",
}

// Azure Semantic VAD (English optimized)
turnDetection: {
  type: "azure_semantic_vad_en",
}

// Azure Semantic VAD (Multilingual)
turnDetection: {
  type: "azure_semantic_vad_multilingual",
}

Audio Formats

Format	Sample Rate	Use Case
pcm16	24kHz	Default, high quality
pcm16-8000hz	8kHz	Telephony
pcm16-16000hz	16kHz	Voice assistants
g711_ulaw	8kHz	Telephony (US)
g711_alaw	8kHz	Telephony (EU)

Key Types Reference

Type	Purpose
VoiceLiveClient	Main client for creating sessions
VoiceLiveSession	Active WebSocket session
VoiceLiveSessionHandlers	Event handler interface
VoiceLiveSubscription	Active event subscription
ConnectionContext	Context for connection events
SessionContext	Context for session events
ServerEventUnion	Union of all server events

Error Handling

import {
  VoiceLiveError,
  VoiceLiveConnectionError,
  VoiceLiveAuthenticationError,
  VoiceLiveProtocolError,
} from "@azure/ai-voicelive";

const subscription = session.subscribe({
  onError: async (args, context) => {
    const { error } = args;
    
    if (error instanceof VoiceLiveConnectionError) {
      console.error("Connection error:", error.message);
    } else if (error instanceof VoiceLiveAuthenticationError) {
      console.error("Auth error:", error.message);
    } else if (error instanceof VoiceLiveProtocolError) {
      console.error("Protocol error:", error.message);
    }
  },
  
  onServerError: async (event, context) => {
    console.error("Server error:", event.error?.message);
  },
});

Logging

import { setLogLevel } from "@azure/logger";

// Enable verbose logging
setLogLevel("info");

// Or via environment variable
// AZURE_LOG_LEVEL=info

Browser Usage

// Browser requires bundler (Vite, webpack, etc.)
import { VoiceLiveClient } from "@azure/ai-voicelive";
import { InteractiveBrowserCredential } from "@azure/identity";

// Use browser-compatible credential
const credential = new InteractiveBrowserCredential({
  clientId: "your-client-id",
  tenantId: "your-tenant-id",
});

const client = new VoiceLiveClient(endpoint, credential);

// Request microphone access
const stream = await navigator.mediaDevices.getUserMedia({ audio: true });
const audioContext = new AudioContext({ sampleRate: 24000 });

// Process audio and send to session
// ... (see samples for full implementation)

Best Practices

1. Use DefaultAzureCredential for local development; use ManagedIdentityCredential or WorkloadIdentityCredential for production — Never hardcode API keys
2. Set both modalities — Include ["text", "audio"] for voice assistants
3. Use Azure Semantic VAD — Better turn detection than basic server VAD
4. Handle all error types — Connection, auth, and protocol errors
5. Clean up subscriptions — Call subscription.close() when done
6. Use appropriate audio format — PCM16 at 24kHz for best quality

Reference Links

Resource	URL
npm Package	https://www.npmjs.com/package/@azure/ai-voicelive
GitHub Source	https://github.com/Azure/azure-sdk-for-js/tree/main/sdk/ai/ai-voicelive
Samples	https://github.com/Azure/azure-sdk-for-js/tree/main/sdk/ai/ai-voicelive/samples
API Reference	https://learn.microsoft.com/javascript/api/@azure/ai-voicelive