> ## Documentation Index
> Fetch the complete documentation index at: https://docs.modulate.ai/llms.txt
> Use this file to discover all available pages before exploring further.

# Deepfake Detection Streaming

> Real-time deepfake detection over WebSocket, with per-frame verdicts and confidence scores delivered as analysis windows complete.

Real-time synthetic voice detection over WebSocket. Streams audio to the server and receives per-frame verdicts (`synthetic`, `non-synthetic`, or `no-content`) with confidence scores as analysis windows complete.

For a conceptual explanation of how detection works — including windowing, silence trimming, and the `no-content` verdict — see [How synthetic voice detection works](/guides/synthetic-voice-detection).

## Endpoint

```text theme={null}
wss://platform.modulate.ai/api/velma-2-synthetic-voice-detection-streaming
```

## Authentication

Pass your API key as a query parameter when opening the connection.

```text theme={null}
wss://platform.modulate.ai/api/velma-2-synthetic-voice-detection-streaming?api_key=YOUR_API_KEY&audio_format=s16le&sample_rate=16000&num_channels=1
```

<Warning>
  Unlike the batch endpoint, the streaming API does not use an `X-API-Key` header. The key must be in the query string at connection time.
</Warning>

## Query parameters

| Parameter      | Type    | Required    | Description                                                                                                          |
| -------------- | ------- | ----------- | -------------------------------------------------------------------------------------------------------------------- |
| `api_key`      | string  | Yes         | Your API key                                                                                                         |
| `audio_format` | string  | Yes         | Audio encoding format — see [Audio formats and preprocessing](/guides/audio-formats)                                 |
| `sample_rate`  | integer | Conditional | Required for raw (headerless) formats. One of: `8000`, `11025`, `16000`, `22050`, `32000`, `44100`, `48000`, `96000` |
| `num_channels` | integer | Conditional | Required for raw formats. 1–8                                                                                        |

For supported format values and format selection guidance, see [Audio formats and preprocessing](/guides/audio-formats).

## Connection flow

1. Connect with `api_key`, `audio_format`, and (for raw formats) `sample_rate` and `num_channels`.
2. Stream audio as **binary** WebSocket frames. Frames can be any size.
3. Receive `frame` JSON messages as analysis windows complete.
4. Send an **empty text frame** (`""`) to signal end of audio.
5. Receive a `done` message with total duration and frame count.
6. The connection closes automatically.

## Server messages

### Frame result

Sent each time an analysis window is complete.

```json theme={null}
{
  "type": "frame",
  "frame": {
    "start_time_ms": 0,
    "end_time_ms": 4000,
    "verdict": "synthetic",
    "confidence": 0.9732
  }
}
```

| Field           | Type    | Description                                         |
| --------------- | ------- | --------------------------------------------------- |
| `start_time_ms` | integer | Frame start time in the audio stream (ms)           |
| `end_time_ms`   | integer | Frame end time in the audio stream (ms)             |
| `verdict`       | string  | `"synthetic"`, `"non-synthetic"`, or `"no-content"` |
| `confidence`    | float   | Confidence in the verdict, 0.0–1.0                  |

### Done

```json theme={null}
{
  "type": "done",
  "duration_ms": 12500,
  "frame_count": 10
}
```

| Field         | Type    | Description                                          |
| ------------- | ------- | ---------------------------------------------------- |
| `duration_ms` | integer | Total duration of the streamed audio in milliseconds |
| `frame_count` | integer | Total number of frames analyzed                      |

### Error

```json theme={null}
{
  "type": "error",
  "error": "Invalid audio_format='mp4'. Valid values: ['aac', 'aiff', ...]"
}
```

## WebSocket close codes

| Code   | Meaning                                                                                  |
| ------ | ---------------------------------------------------------------------------------------- |
| `1000` | Normal closure after a successful `done` message                                         |
| `1003` | Invalid query parameters (bad format, sample rate, or channels)                          |
| `4002` | Audio could not be decoded or does not match the declared format                         |
| `4003` | Request could not be validated, or is not permitted (auth failure, missing model access) |
| `4029` | Insufficient credits, or concurrent-connection limit exceeded                            |

An `error` JSON message is sent before the connection closes (except on `1000`).

## Rate limits

* Concurrent connection limits apply per organization.
* Monthly usage limits (in audio hours) apply per organization.
* Connections that exceed limits are rejected during the WebSocket handshake with close code `4029`.

## Related

* [How synthetic voice detection works](/guides/synthetic-voice-detection) — windowing, silence trimming, and scoring explained
* [Audio formats and preprocessing](/guides/audio-formats) — format options for the streaming endpoint
* [Which API should I use?](/guides/which-api) — batch vs streaming tradeoffs
* [Authentication and rate limits](/guides/authentication)