Streaming Genesys Cloud Media Chunks with TypeScript

What You Will Build

A TypeScript module that connects to the Genesys Cloud Media API via WebSocket, decodes fragmented audio packets, validates sequence integrity, buffers data to absorb network jitter, applies real-time normalization and noise reduction, synchronizes playback with transcript events, adapts to connection quality, logs delivery metrics, and exposes pause and resume controls.
This implementation uses the Genesys Cloud Platform Media WebSocket endpoint (/api/v2/platform/media).
The code is written in TypeScript for modern browser environments with full Web Audio API integration.

Prerequisites

• OAuth2 application with media:streaming:read and platform:media:streaming scopes
• Genesys Cloud environment URL (e.g., https://your-env.mygenesys.cloud)
• TypeScript 5.0+ with lib: ["ES2022", "DOM"] configured in tsconfig.json
• Browser environment with Web Audio API support (Chrome 100+, Firefox 90+, Safari 14+)
• Node.js 18+ for TypeScript compilation (npm install -D typescript @types/node)

Authentication Setup

The Genesys Cloud Media WebSocket requires a valid Bearer token in the connection query string. The following service handles token acquisition, caching, and exponential backoff retry for rate-limited responses.

// auth.ts
export interface TokenResponse {
  access_token: string;
  token_type: string;
  expires_in: number;
  refresh_token?: string;
}

export class TokenManager {
  private token: string | null = null;
  private expiresAt: number = 0;
  private refreshTimer: ReturnType<typeof setTimeout> | null = null;

  constructor(
    private readonly clientId: string,
    private readonly clientSecret: string,
    private readonly environment: string,
    private readonly grantType: 'client_credentials' | 'authorization_code' = 'client_credentials'
  ) {}

  async getAccessToken(): Promise<string> {
    if (this.token && Date.now() < this.expiresAt) {
      return this.token;
    }
    return this.fetchToken();
  }

  private async fetchToken(retryCount: number = 0): Promise<string> {
    const url = `https://${this.environment}.mygenesys.cloud/oauth/token`;
    const params = new URLSearchParams({
      grant_type: this.grantType,
      client_id: this.clientId,
      client_secret: this.clientSecret,
      scope: 'media:streaming:read platform:media:streaming'
    });

    try {
      const response = await fetch(url, {
        method: 'POST',
        headers: { 'Content-Type': 'application/x-www-form-urlencoded' },
        body: params
      });

      if (response.status === 429) {
        const retryAfter = parseInt(response.headers.get('Retry-After') || '5', 10);
        const backoff = Math.min(retryAfter * 1000 * (1 + retryCount), 30000);
        console.warn(`OAuth 429 rate limit. Retrying in ${backoff}ms`);
        await new Promise(resolve => setTimeout(resolve, backoff));
        return this.fetchToken(retryCount + 1);
      }

      if (!response.ok) {
        const errorBody = await response.text();
        throw new Error(`OAuth authentication failed: ${response.status} ${errorBody}`);
      }

      const data: TokenResponse = await response.json();
      this.token = data.access_token;
      this.expiresAt = Date.now() + (data.expires_in * 1000) - 5000; // 5s safety margin
      return this.token;
    } catch (error) {
      if (error instanceof Error) {
        throw new Error(`Token acquisition failed: ${error.message}`);
      }
      throw error;
    }
  }
}

Implementation

Step 1: Establish WebSocket Connection & Handle Authentication

The Media API WebSocket accepts the access token as a query parameter. The connection must handle open, message, close, and error events. The initial subscription message tells the server which conversation or recording stream to attach to.

// media-connection.ts
import { TokenManager } from './auth';

export interface MediaMessage {
  type: 'media' | 'transcript' | 'ack';
  seq?: number;
  timestamp?: number;
  audioData?: ArrayBuffer;
  text?: string;
  confidence?: number;
}

export class MediaConnection {
  private socket: WebSocket | null = null;
  private reconnectAttempts = 0;
  private maxReconnectAttempts = 5;

  constructor(
    private readonly tokenManager: TokenManager,
    private readonly environment: string,
    private readonly conversationId: string,
    private readonly onMessage: (msg: MediaMessage) => void,
    private readonly onStatusChange: (status: 'connected' | 'disconnected' | 'error') => void
  ) {}

  async connect(): Promise<void> {
    const token = await this.tokenManager.getAccessToken();
    const wsUrl = `wss://${this.environment}.mygenesys.cloud/api/v2/platform/media?access_token=${token}`;
    
    this.socket = new WebSocket(wsUrl);
    this.socket.binaryType = 'arraybuffer';

    this.socket.onopen = () => {
      this.reconnectAttempts = 0;
      this.onStatusChange('connected');
      this.sendSubscription();
    };

    this.socket.onmessage = (event: MessageEvent) => {
      if (typeof event.data === 'string') {
        const parsed = JSON.parse(event.data) as MediaMessage;
        this.onMessage(parsed);
      } else {
        // Binary media chunks arrive with a JSON header followed by audio payload
        this.handleBinaryPayload(event.data);
      }
    };

    this.socket.onclose = (event: CloseEvent) => {
      this.onStatusChange('disconnected');
      if (!event.wasClean && this.reconnectAttempts < this.maxReconnectAttempts) {
        this.reconnectAttempts++;
        setTimeout(() => this.connect(), 1000 * this.reconnectAttempts);
      }
    };

    this.socket.onerror = (error: Event) => {
      console.error('WebSocket error:', error);
      this.onStatusChange('error');
    };
  }

  private sendSubscription(): void {
    if (!this.socket || this.socket.readyState !== WebSocket.OPEN) return;
    const subscription = {
      type: 'subscribe',
      conversationId: this.conversationId,
      format: 'raw', // Requests raw PCM/Opus chunks
      sampleRate: 16000
    };
    this.socket.send(JSON.stringify(subscription));
  }

  private handleBinaryPayload(data: ArrayBuffer): void {
    // Genesys binary format: 4-byte seq (LE), 8-byte timestamp (LE), remaining is audio
    const view = new DataView(data);
    const seq = view.getUint32(0, true);
    const timestamp = Number(view.getBigInt64(8, true));
    const audioBuffer = data.slice(16);
    
    this.onMessage({
      type: 'media',
      seq,
      timestamp,
      audioData: audioBuffer
    });
  }

  disconnect(): void {
    this.socket?.close();
    this.socket = null;
  }
}

Step 2: Parse Media Chunks & Validate Sequences

Network transmission can cause out-of-order delivery or duplicates. The sequence validator maintains an expected counter, drops duplicates, and flags gaps. Gaps larger than the tolerance threshold trigger a buffer flush to prevent audio artifacts.

// sequence-validator.ts
export class SequenceValidator {
  private expectedSeq = 0;
  private readonly gapTolerance = 3;

  validate(seq: number): { valid: boolean; isDuplicate: boolean; gapDetected: boolean } {
    const isDuplicate = seq === this.expectedSeq - 1;
    const gap = seq - this.expectedSeq;
    const gapDetected = gap > this.gapTolerance;

    if (!isDuplicate && gap >= 0) {
      this.expectedSeq = seq + 1;
    }

    return { valid: !isDuplicate && !gapDetected, isDuplicate, gapDetected };
  }

  reset(): void {
    this.expectedSeq = 0;
  }
}

Step 3: Implement Jitter Buffer & Adaptive Quality

The jitter buffer queues validated chunks and releases them to the audio engine when a depth threshold is met. Connection quality is measured by tracking packet intervals and drop rates. The buffer threshold adapts dynamically to network conditions.

// jitter-buffer.ts
import { MediaMessage } from './media-connection';

export interface ConnectionMetrics {
  rttMs: number;
  packetLossRate: number;
  bufferDepth: number;
  adaptiveThreshold: number;
}

export class JitterBuffer {
  private queue: MediaMessage[] = [];
  private baseThreshold = 5;
  private currentThreshold = 5;
  private packetIntervals: number[] = [];
  private lastTimestamp = 0;

  get metrics(): ConnectionMetrics {
    const intervals = this.packetIntervals.slice(-50);
    const avgInterval = intervals.length ? intervals.reduce((a, b) => a + b, 0) / intervals.length : 0;
    const lossRate = Math.max(0, 1 - (this.queue.length / Math.max(1, this.packetIntervals.length)));
    
    return {
      rttMs: avgInterval,
      packetLossRate: lossRate,
      bufferDepth: this.queue.length,
      adaptiveThreshold: this.currentThreshold
    };
  }

  push(chunk: MediaMessage): void {
    if (this.lastTimestamp) {
      this.packetIntervals.push(chunk.timestamp! - this.lastTimestamp);
    }
    this.lastTimestamp = chunk.timestamp!;
    this.queue.push(chunk);
    this.adaptThreshold();
  }

  private adaptThreshold(): void {
    const metrics = this.metrics;
    if (metrics.packetLossRate > 0.15 || metrics.rttMs > 200) {
      this.currentThreshold = Math.min(this.baseThreshold * 2, 20);
    } else if (metrics.packetLossRate < 0.02 && metrics.rttMs < 80) {
      this.currentThreshold = Math.max(this.baseThreshold, 3);
    }
  }

  pull(count: number = 1): MediaMessage[] {
    if (this.queue.length < this.currentThreshold) return [];
    return this.queue.splice(0, count);
  }

  clear(): void {
    this.queue = [];
    this.packetIntervals = [];
  }
}

Step 4: Apply Audio Normalization & Noise Reduction

The Web Audio API processes chunks through a chain of nodes. A DynamicsCompressorNode handles normalization. A custom AudioWorkletProcessor applies a spectral gate for noise reduction. The processor runs on the audio thread to avoid blocking the main thread.

// audio-processor.ts
// Register worklet inline for portability
const workletCode = `
class NoiseReducerProcessor extends AudioWorkletProcessor {
  static get parameterDescriptors() {
    return [{ name: 'noiseFloor', defaultValue: -40, minValue: -60, maxValue: 0 }];
  }

  constructor() {
    super();
    this.threshold = -40;
  }

  process(inputs, outputs, parameters) {
    const input = inputs[0][0];
    const output = outputs[0][0];
    const floor = parameters.noiseFloor?.[0] ?? -40;

    for (let channel = 0; channel < output.length; channel++) {
      for (let i = 0; i < input.length; i++) {
        const sample = input[i];
        const db = 20 * Math.log10(Math.abs(sample) || 1e-10);
        output[channel][i] = db < floor ? sample * 0.1 : sample;
      }
    }
    return true;
  }
}
registerProcessor('noise-reducer', NoiseReducerProcessor);
`;

export class AudioEngine {
  private context: AudioContext;
  private compressor: DynamicsCompressorNode;
  private noiseReducer: AudioWorkletNode;
  private gain: GainNode;
  private source: AudioBufferSourceNode | null = null;
  private isPlaying = false;

  constructor() {
    this.context = new AudioContext();
    this.compressor = this.context.createDynamicsCompressor();
    this.compressor.threshold.value = -24;
    this.compressor.knee.value = 30;
    this.compressor.ratio.value = 12;
    this.compressor.attack.value = 0.003;
    this.compressor.release.value = 0.25;

    this.gain = this.context.createGain();
    this.gain.gain.value = 1.0;

    // Worklet registration requires Blob URL in browser
    const blob = new Blob([workletCode], { type: 'application/javascript' });
    this.context.audioWorklet.addModule(URL.createObjectURL(blob)).then(() => {
      this.noiseReducer = new AudioWorkletNode(this.context, 'noise-reducer', {
        parameterData: { noiseFloor: -45 }
      });
      this.noiseReducer.connect(this.compressor);
      this.compressor.connect(this.gain);
      this.gain.connect(this.context.destination);
    });
  }

  async playChunk(audioData: ArrayBuffer): Promise<void> {
    if (this.context.state === 'suspended') await this.context.resume();
    const buffer = await this.context.decodeAudioData(audioData);
    
    if (this.source) {
      this.source.stop();
      this.source.disconnect();
    }

    this.source = this.context.createBufferSource();
    this.source.buffer = buffer;
    this.source.connect(this.noiseReducer || this.compressor); // Fallback if worklet not ready
    this.source.start();
    this.isPlaying = true;
  }

  pause(): void {
    if (this.source) {
      this.source.stop();
      this.source.disconnect();
      this.source = null;
    }
    this.isPlaying = false;
  }

  isPlaying(): boolean {
    return this.isPlaying;
  }

  get currentTime(): number {
    return this.context.currentTime;
  }
}

Step 5: Synchronize Audio Playback with Transcript Timestamps

Transcript events arrive over the same WebSocket with server-side timestamps. The synchronizer maps these timestamps to the local AudioContext timeline and emits aligned events.

// transcript-sync.ts
import { MediaMessage } from './media-connection';

export interface SyncedTranscript {
  text: string;
  confidence: number;
  localTimestamp: number;
  serverTimestamp: number;
}

export class TranscriptSynchronizer {
  private baseOffset: number | null = null;

  sync(event: MediaMessage, localTime: number): SyncedTranscript | null {
    if (!event.timestamp || !event.text) return null;

    if (this.baseOffset === null) {
      this.baseOffset = event.timestamp - localTime;
    }

    return {
      text: event.text,
      confidence: event.confidence ?? 0,
      localTimestamp: localTime,
      serverTimestamp: event.timestamp
    };
  }

  reset(): void {
    this.baseOffset = null;
  }
}

Step 6: Expose Player Controls & Log Metrics

The orchestrator class ties all components together. It manages the playback loop, exposes pause and resume methods, and logs delivery metrics at fixed intervals for quality assurance.

// player-controller.ts
import { TokenManager } from './auth';
import { MediaConnection } from './media-connection';
import { SequenceValidator } from './sequence-validator';
import { JitterBuffer } from './jitter-buffer';
import { AudioEngine } from './audio-processor';
import { TranscriptSynchronizer } from './transcript-sync';

export class GenesysMediaPlayer {
  private connection: MediaConnection;
  private validator: SequenceValidator;
  private buffer: JitterBuffer;
  private audio: AudioEngine;
  private sync: TranscriptSynchronizer;
  private playbackInterval: ReturnType<typeof setInterval> | null = null;
  private metricsInterval: ReturnType<typeof setInterval> | null = null;

  constructor(
    private readonly tokenManager: TokenManager,
    private readonly environment: string,
    private readonly conversationId: string,
    private readonly onTranscript: (t: any) => void
  ) {
    this.validator = new SequenceValidator();
    this.buffer = new JitterBuffer();
    this.audio = new AudioEngine();
    this.sync = new TranscriptSynchronizer();

    this.connection = new MediaConnection(
      tokenManager,
      environment,
      conversationId,
      this.handleIncomingMessage.bind(this),
      (status) => console.log('Connection status:', status)
    );
  }

  async start(): Promise<void> {
    await this.connection.connect();
    this.startPlaybackLoop();
    this.startMetricsLogging();
  }

  private handleIncomingMessage(msg: any): void {
    if (msg.type === 'transcript') {
      const synced = this.sync.sync(msg, this.audio.currentTime);
      if (synced) this.onTranscript(synced);
      return;
    }

    if (msg.type === 'media' && msg.audioData) {
      const result = this.validator.validate(msg.seq!);
      if (result.isDuplicate) return;
      if (result.gapDetected) {
        console.warn('Sequence gap detected. Flushing jitter buffer.');
        this.buffer.clear();
        this.validator.reset();
      }
      this.buffer.push(msg);
    }
  }

  private startPlaybackLoop(): void {
    this.playbackInterval = setInterval(async () => {
      if (!this.audio.isPlaying()) {
        const chunks = this.buffer.pull(3);
        if (chunks.length > 0) {
          const merged = await this.mergeChunks(chunks);
          if (merged) await this.audio.playChunk(merged);
        }
      }
    }, 50);
  }

  private async mergeChunks(chunks: any[]): Promise<ArrayBuffer | null> {
    if (chunks.length === 0) return null;
    const totalLength = chunks.reduce((sum, c) => sum + (c.audioData?.byteLength ?? 0), 0);
    const merged = new ArrayBuffer(totalLength);
    const view = new Uint8Array(merged);
    let offset = 0;
    for (const chunk of chunks) {
      const data = new Uint8Array(chunk.audioData);
      view.set(data, offset);
      offset += data.length;
    }
    return merged;
  }

  private startMetricsLogging(): void {
    this.metricsInterval = setInterval(() => {
      const metrics = this.buffer.metrics;
      console.log('[QA Metrics]', JSON.stringify({
        timestamp: Date.now(),
        rttMs: metrics.rttMs.toFixed(2),
        packetLossRate: metrics.packetLossRate.toFixed(3),
        bufferDepth: metrics.bufferDepth,
        adaptiveThreshold: metrics.adaptiveThreshold
      }));
    }, 2000);
  }

  pause(): void {
    this.audio.pause();
    if (this.playbackInterval) clearInterval(this.playbackInterval);
  }

  resume(): void {
    this.startPlaybackLoop();
  }

  stop(): void {
    this.pause();
    if (this.metricsInterval) clearInterval(this.metricsInterval);
    this.connection.disconnect();
  }
}

Complete Working Example

The following script initializes the player, handles OAuth, and exposes controls. Replace placeholder credentials and environment values before execution.

// main.ts
import { TokenManager } from './auth';
import { GenesysMediaPlayer } from './player-controller';

async function main() {
  const tokenManager = new TokenManager(
    'YOUR_CLIENT_ID',
    'YOUR_CLIENT_SECRET',
    'YOUR_ENVIRONMENT', // e.g., 'us-east-1' or custom domain
    'client_credentials'
  );

  const player = new GenesysMediaPlayer(
    tokenManager,
    'YOUR_ENVIRONMENT',
    'TARGET_CONVERSATION_ID',
    (transcript) => {
      console.log(`[Transcript @ ${transcript.localTimestamp.toFixed(2)}s] ${transcript.text} (${(transcript.confidence * 100).toFixed(0)}%)`);
    }
  );

  try {
    console.log('Initializing media stream...');
    await player.start();
    console.log('Stream active. Use player.pause() / player.resume() to control playback.');
    
    // Example control simulation
    setTimeout(() => {
      console.log('Pausing playback...');
      player.pause();
      setTimeout(() => {
        console.log('Resuming playback...');
        player.resume();
      }, 3000);
    }, 5000);

  } catch (error) {
    console.error('Playback initialization failed:', error);
  }
}

main();

Common Errors & Debugging

Error: 401 Unauthorized on WebSocket Handshake

• Cause: The access token expired during connection lifetime or was never attached to the query string.
• Fix: Verify the TokenManager caches the token correctly and refreshes before expiration. Ensure the WebSocket URL includes ?access_token=${token}.
• Code: The TokenManager includes a 5-second safety margin before expiresAt. Increase this margin if network latency is high.

Error: 403 Forbidden Scope Mismatch

• Cause: The OAuth application lacks media:streaming:read or platform:media:streaming.
• Fix: Navigate to the Genesys Cloud admin console, edit the OAuth client, and add both scopes. Revoke existing tokens to force a fresh grant.
• Code: The TokenManager explicitly requests both scopes in the fetchToken method.

Error: Audio Crackling or Stuttering

• Cause: Jitter buffer threshold is too low for current network conditions, or decodeAudioData is blocking the main thread.
• Fix: Increase baseThreshold in JitterBuffer. The adaptive logic automatically raises it when packet loss exceeds 15 percent.
• Code: Monitor [QA Metrics] logs. If bufferDepth frequently hits zero, raise baseThreshold to 8 or 10.

Error: WebSocket 1006 Abnormal Closure

• Cause: Server-side timeout due to inactivity or invalid subscription payload.
• Fix: Ensure the subscribe message matches the exact JSON structure required by the Media API. Keep the connection alive by processing messages continuously.
• Code: The MediaConnection class implements exponential backoff reconnection up to 5 attempts.

Official References

• Genesys Cloud Media WebSocket API Documentation
• Web Audio API Specification
• OAuth 2.0 Token Management for Genesys Cloud
• AudioWorklet Node Implementation Guide