Telnyx Voice Streaming Javascript

---
name: telnyx-voice-streaming-javascript
description: >-
  Stream call audio in real-time, fork media to external destinations, and
  transcribe speech live. Use for real-time analytics and AI integrations. This
  skill provides JavaScript SDK examples.
metadata:
  author: telnyx
  product: voice-streaming
  language: javascript
  generated_by: telnyx-openapi-pipeline
---

<!-- Auto-generated from Telnyx OpenAPI specs. Do not edit. -->

# Telnyx Voice Streaming - JavaScript

## Installation

```bash
npm install telnyx@6.74.2
```

## Setup

```javascript
import Telnyx from 'telnyx';

const client = new Telnyx({
  apiKey: process.env['TELNYX_API_KEY'], // This is the default and can be omitted
});
```

All examples below assume `client` is already initialized as shown above.

## Error Handling

All API calls can fail with network errors, rate limits (429), validation errors (422),
or authentication errors (401). Always handle errors in production code:

```javascript
try {
  const result = await client.messages.send({ to: '+13125550001', from: '+13125550002', text: 'Hello' });
} catch (err) {
  if (err instanceof Telnyx.APIConnectionError) {
    console.error('Network error — check connectivity and retry');
  } else if (err instanceof Telnyx.RateLimitError) {
    // 429: rate limited — wait and retry with exponential backoff
    const retryAfter = err.headers?.['retry-after'] || 1;
    await new Promise(r => setTimeout(r, retryAfter * 1000));
  } else if (err instanceof Telnyx.APIError) {
    console.error(`API error ${err.status}: ${err.message}`);
    if (err.status === 422) {
      console.error('Validation error — check required fields and formats');
    }
  }
}
```

Common error codes: `401` invalid API key, `403` insufficient permissions,
`404` resource not found, `422` validation error (check field formats),
`429` rate limited (retry with exponential backoff).

## Forking start

Call forking allows you to stream the media from a call to a specific target in realtime. This stream can be used to enable realtime audio analysis to support a 
variety of use cases, including fraud detection, or the creation of AI-generated audio responses. Requests must specify either the `target` attribute or the `rx` and `tx` attributes.

`POST /calls/{call_control_id}/actions/fork_start`

Optional: `client_state` (string), `command_id` (string), `rx` (string), `stream_type` (enum: decrypted), `tx` (string)

```javascript
const response = await client.calls.actions.startForking('v3:550e8400-e29b-41d4-a716-446655440000_gRU1OGRkYQ');

console.log(response.data);
```

Returns: `result` (string)

## Forking stop

Stop forking a call. **Expected Webhooks:**

- `call.fork.stopped`

`POST /calls/{call_control_id}/actions/fork_stop`

Optional: `client_state` (string), `command_id` (string), `stream_type` (enum: raw, decrypted)

```javascript
const response = await client.calls.actions.stopForking('v3:550e8400-e29b-41d4-a716-446655440000_gRU1OGRkYQ');

console.log(response.data);
```

Returns: `result` (string)

## Streaming start

Start streaming the media from a call to a specific WebSocket address or Dialogflow connection in near-realtime. Audio will be delivered as base64-encoded RTP payload (raw audio), wrapped in JSON payloads. Please find more details about media streaming messages specification under the [link](https://developers.telnyx.com/docs/voice/programmable-voice/media-streaming).

`POST /calls/{call_control_id}/actions/streaming_start`

Optional: `client_state` (string), `command_id` (string), `custom_parameters` (array[object]), `dialogflow_config` (object), `enable_dialogflow` (boolean), `stream_auth_token` (string), `stream_bidirectional_codec` (enum: PCMU, PCMA, G722, OPUS, AMR-WB, L16), `stream_bidirectional_mode` (enum: mp3, rtp), `stream_bidirectional_sampling_rate` (enum: 8000, 16000, 22050, 24000, 48000), `stream_bidirectional_target_legs` (enum: both, self, opposite), `stream_codec` (enum: PCMU, PCMA, G722, OPUS, AMR-WB, L16, default), `stream_track` (enum: inbound_track, outbound_track, both_tracks), `stream_url` (string)

```javascript
const response = await client.calls.actions.startStreaming('v3:550e8400-e29b-41d4-a716-446655440000_gRU1OGRkYQ');

console.log(response.data);
```

Returns: `result` (string)

## Streaming stop

Stop streaming a call to a WebSocket. **Expected Webhooks:**

- `streaming.stopped`

`POST /calls/{call_control_id}/actions/streaming_stop`

Optional: `client_state` (string), `command_id` (string), `stream_id` (uuid)

```javascript
const response = await client.calls.actions.stopStreaming('v3:550e8400-e29b-41d4-a716-446655440000_gRU1OGRkYQ');

console.log(response.data);
```

Returns: `result` (string)

## Transcription start

Start real-time transcription. Transcription will stop on call hang-up, or can be initiated via the Transcription stop command. **Expected Webhooks:**

- `call.transcription`

`POST /calls/{call_control_id}/actions/transcription_start`

Optional: `client_state` (string), `command_id` (string), `transcription_engine` (enum: Google, Telnyx, Deepgram, Azure, xAI, AssemblyAI, Speechmatics, Soniox, Parakeet, A, B), `transcription_engine_config` (object), `transcription_tracks` (string)

```javascript
const response = await client.calls.actions.startTranscription('v3:550e8400-e29b-41d4-a716-446655440000_gRU1OGRkYQ');

console.log(response.data);
```

Returns: `result` (string)

## Transcription stop

Stop real-time transcription.

`POST /calls/{call_control_id}/actions/transcription_stop`

Optional: `client_state` (string), `command_id` (string)

```javascript
const response = await client.calls.actions.stopTranscription('v3:550e8400-e29b-41d4-a716-446655440000_gRU1OGRkYQ');

console.log(response.data);
```

Returns: `result` (string)

---

## Webhooks

### Webhook Verification

Telnyx signs webhooks with Ed25519. Each request includes `telnyx-signature-ed25519`
and `telnyx-timestamp` headers. Always verify signatures in production:

```javascript
// In your webhook handler (e.g., Express — use raw body, not parsed JSON):
app.post('/webhooks', express.raw({ type: 'application/json' }), async (req, res) => {
  try {
    const event = await client.webhooks.unwrap(req.body.toString(), {
      headers: req.headers,
    });
    // Signature valid — event is the parsed webhook payload
    console.log('Received event:', event.data.event_type);
    res.status(200).send('OK');
  } catch (err) {
    console.error('Webhook verification failed:', err.message);
    res.status(400).send('Invalid signature');
  }
});
```

The following webhook events are sent to your configured webhook URL.
All webhooks include `telnyx-timestamp` and `telnyx-signature-ed25519` headers for Ed25519 signature verification. Use `client.webhooks.unwrap()` to verify.

| Event | Description |
|-------|-------------|
| `callForkStarted` | Call Fork Started |
| `callForkStopped` | Call Fork Stopped |
| `callStreamingFailed` | Call Streaming Failed |
| `callStreamingStarted` | Call Streaming Started |
| `callStreamingStopped` | Call Streaming Stopped |
| `transcription` | Transcription |

### Webhook payload fields

**`callForkStarted`**

| Field | Type | Description |
|-------|------|-------------|
| `data.record_type` | enum: event | Identifies the type of the resource. |
| `data.event_type` | enum: call.fork.started | The type of event being delivered. |
| `data.id` | uuid | Identifies the type of resource. |
| `data.occurred_at` | date-time | ISO 8601 datetime of when the event occurred. |
| `data.payload.connection_id` | string | Call Control App ID (formerly Telnyx connection ID) used in the call. |
| `data.payload.call_control_id` | string | Unique ID for controlling the call. |
| `data.payload.call_leg_id` | string | ID that is unique to the call and can be used to correlate webhook events. |
| `data.payload.call_session_id` | string | ID that is unique to the call session and can be used to correlate webhook events. |
| `data.payload.client_state` | string | State received from a command. |
| `data.payload.stream_type` | enum: decrypted | Type of media streamed. |

**`callForkStopped`**

| Field | Type | Description |
|-------|------|-------------|
| `data.record_type` | enum: event | Identifies the type of the resource. |
| `data.event_type` | enum: call.fork.stopped | The type of event being delivered. |
| `data.id` | uuid | Identifies the type of resource. |
| `data.occurred_at` | date-time | ISO 8601 datetime of when the event occurred. |
| `data.payload.connection_id` | string | Call Control App ID (formerly Telnyx connection ID) used in the call. |
| `data.payload.call_control_id` | string | Unique ID for controlling the call. |
| `data.payload.call_leg_id` | string | ID that is unique to the call and can be used to correlate webhook events. |
| `data.payload.call_session_id` | string | ID that is unique to the call session and can be used to correlate webhook events. |
| `data.payload.client_state` | string | State received from a command. |
| `data.payload.stream_type` | enum: decrypted | Type of media streamed. |

**`callStreamingFailed`**

| Field | Type | Description |
|-------|------|-------------|
| `data.record_type` | enum: event | Identifies the resource. |
| `data.event_type` | enum: streaming.failed | The type of event being delivered. |
| `data.id` | uuid | Identifies the type of resource. |
| `data.occurred_at` | date-time | ISO 8601 datetime of when the event occurred. |
| `data.payload.call_control_id` | string | Call ID used to issue commands via Call Control API. |
| `data.payload.connection_id` | string | Call Control App ID (formerly Telnyx connection ID) used in the call. |
| `data.payload.call_leg_id` | string | ID that is unique to the call and can be used to correlate webhook events. |
| `data.payload.call_session_id` | string | ID that is unique to the call session and can be used to correlate webhook events. |
| `data.payload.client_state` | string | State received from a command. |
| `data.payload.failure_reason` | string | A short description explaning why the media streaming failed. |
| `data.payload.stream_id` | uuid | Identifies the streaming. |
| `data.payload.stream_type` | enum: websocket, dialogflow | The type of stream connection the stream is performing. |

**`callStreamingStarted`**

| Field | Type | Description |
|-------|------|-------------|
| `data.record_type` | enum: event | Identifies the type of the resource. |
| `data.event_type` | enum: streaming.started | The type of event being delivered. |
| `data.id` | uuid | Identifies the type of resource. |
| `data.occurred_at` | date-time | ISO 8601 datetime of when the event occurred. |
| `data.payload.call_control_id` | string | Call ID used to issue commands via Call Control API. |
| `data.payload.connection_id` | string | Call Control App ID (formerly Telnyx connection ID) used in the call. |
| `data.payload.call_leg_id` | string | ID that is unique to the call and can be used to correlate webhook events. |
| `data.payload.call_session_id` | string | ID that is unique to the call session and can be used to correlate webhook events. |
| `data.payload.client_state` | string | State received from a command. |
| `data.payload.stream_url` | string | Destination WebSocket address where the stream is going to be delivered. |

**`callStreamingStopped`**

| Field | Type | Description |
|-------|------|-------------|
| `data.record_type` | enum: event | Identifies the type of the resource. |
| `data.event_type` | enum: streaming.stopped | The type of event being delivered. |
| `data.id` | uuid | Identifies the type of resource. |
| `data.occurred_at` | date-time | ISO 8601 datetime of when the event occurred. |
| `data.payload.call_control_id` | string | Call ID used to issue commands via Call Control API. |
| `data.payload.connection_id` | string | Call Control App ID (formerly Telnyx connection ID) used in the call. |
| `data.payload.call_leg_id` | string | ID that is unique to the call and can be used to correlate webhook events. |
| `data.payload.call_session_id` | string | ID that is unique to the call session and can be used to correlate webhook events. |
| `data.payload.client_state` | string | State received from a command. |
| `data.payload.stream_url` | string | Destination WebSocket address where the stream is going to be delivered. |

**`transcription`**

| Field | Type | Description |
|-------|------|-------------|
| `data.record_type` | enum: event | Identifies the type of the resource. |
| `data.event_type` | enum: call.transcription | The type of event being delivered. |
| `data.id` | uuid | Identifies the type of resource. |
| `data.occurred_at` | date-time | ISO 8601 datetime of when the event occurred. |
| `data.payload.call_control_id` | string | Unique identifier and token for controlling the call. |
| `data.payload.call_leg_id` | string | ID that is unique to the call and can be used to correlate webhook events. |
| `data.payload.call_session_id` | string | ID that is unique to the call session and can be used to correlate webhook events. |
| `data.payload.client_state` | string | Use this field to add state to every subsequent webhook. |
| `data.payload.connection_id` | string | Call Control App ID (formerly Telnyx connection ID) used in the call. |