---
title: "Detect synthetic voice in an audio file"
method: POST
path: "/api/velma-2-synthetic-voice-detection-batch"
---

# Detect synthetic voice in an audio file

`POST /api/velma-2-synthetic-voice-detection-batch`

Accepts a single audio file and returns a per-frame synthetic-voice
classification across the clip as a synchronous JSON response.
Recommended audio length: 4-60 seconds; files shorter than 0.5 seconds
are rejected with a 422.

## Response `200`

Detection completed successfully.

- DetectionAPIResponse
  - `filename` string, nullable, required — Original filename of the uploaded audio.
  - `frames` FrameResult[], required — Ordered list of per-frame detection results covering the full audio duration.
    - `start_time_ms` integer, required — Frame start time in milliseconds.
    - `end_time_ms` integer, required — Frame end time in milliseconds.
    - `verdict` 'synthetic' | 'non-synthetic' | 'no-content', required — Classification for this frame: - `synthetic` - the frame likely contains AI-generated speech. - `non-synthetic` - the frame likely contains natural human speech. - `no-content` - the frame is silent or contains no usable audio.
    - `confidence` number, double, required — Confidence in the stated verdict, from 0 (lowest) to 1 (highest).
  - `duration_ms` integer, required — Total duration of the audio in milliseconds.

## Other responses

- `400` — Bad request - the uploaded file is empty or its format is not supported.
- `403` — Forbidden - the request is not permitted.
- `422` — Unprocessable entity - the audio is too short to analyze, could not be processed, or a required request parameter is missing or invalid (for example, the `X-API-Key` header or the `upload_file` field).
- `429` — Too many requests - the request could not be completed due to insufficient credits.
- `500` — Internal server error during inference.
- `502` — Bad gateway - the request could not be validated.
- `504` — Gateway timeout - inference did not complete in time.

---

[API](https://skmtc.dev/modulate/apis/velma-2-accent-batch-api.md) · [All operations](https://skmtc.dev/modulate/apis/velma-2-accent-batch-api/llms.txt) · [OpenAPI document](https://skmtc.dev/modulate/apis/velma-2-accent-batch-api/revisions/b4c9ce648efa?raw)