---
title: "LTX Lipsync"
description: "LTX 2.3 turns a still image and a voice track into a short talking clip, with an optional prompt for a small camera or body motion. It is the default lipsync model of the platform."
url: https://docs.roasos.com/models/lipsync/ltx-lipsync
---

# LTX Lipsync

<Callout>
  Family 

  `lipsync`

   · model 

  `ltx-lipsync`

   · catalog 

  `model-catalog@2026-10-06.v5`

   · pricing 

  `customer-pricing@2026-11-05.v15`

  .
</Callout>

## Endpoint

```http
POST https://api.roasos.com/v1/lipsync/ltx-lipsync
```

Send your API key as a bearer token. The key needs the scope `api:write`. Every paid request also needs an `Idempotency-Key` header.

The envelope fields `quote_only`, `quote_id`, `webhook_url` and `wait_timeout_seconds` behave the same on each model endpoint. Refer to [Jobs](/concepts/jobs) and [Quotes and credits](/concepts/quotes-and-credits).

## Good at

Short social cut-downs of 2 to 10 seconds from one image and one audio file. The prompt describes how the image moves ("a woman whispering to the microphone"). Choose it when the take is short and speed matters. It does not re-lip an existing video (use /v1/lipsync/veed-lipsync-v2) and it does not hold identity over a long take (use /v1/lipsync/kling-avatar-v2-pro when it ships). Audio limit: fal states 2–20 s and "pro models support a maximum of 10 seconds". TBD: which limit applies (spec open question 1); keep the audio at 10 s or shorter.

## Pricing

The unit is one **second**. Pricing key: `ltx-lipsync`.

| Request | Credits |
| ------- | ------- |
| `10s`   | 12      |

The credits come from the roasOS pricing table. No other field changes the price. To get the exact price of your request, send it with `quote_only: true` first.

## Modes

* `image-audio-to-video`

Provider endpoints: `fal-ai/ltx-2.3/audio-to-video`.

## Request fields

| Field                  | Type    | Required | Default | Rule                              |
| ---------------------- | ------- | -------- | ------- | --------------------------------- |
| `aspect_ratio`         | enum    | no       | —       | `auto`, `16:9`, `9:16`            |
| `audio_url`            | string  | yes      | —       | https URL; ≤ 4,096 characters     |
| `avatar_id`            | string  | no       | —       | UUID                              |
| `guidance_scale`       | number  | no       | —       | 1–20                              |
| `image_url`            | string  | no       | —       | https URL; ≤ 4,096 characters     |
| `prompt`               | string  | no       | —       | ≥ 1 character; ≤ 5,000 characters |
| `quote_id`             | string  | no       | —       | UUID                              |
| `quote_only`           | boolean | no       | `false` | —                                 |
| `wait_timeout_seconds` | integer | no       | `0`     | 0–60                              |
| `webhook_url`          | string  | no       | —       | https URL; ≤ 4,096 characters     |

The schema is strict. A field that is not in this table gets `400 unsupported_option`. The field names are the roasOS role names. One role has one name in every family.

## Media

This endpoint accepts these media roles:

* `avatar_id` — identity; the saved character reference sheet, with a derived portrait only where the model requires a single face or source frame
* `image_url` — first frame (or the single source image)
* `audio_url` — the driving audio track

| Role        | Items | Maximum size | Content types                                                       | Duration |
| ----------- | ----- | ------------ | ------------------------------------------------------------------- | -------- |
| `audio_url` | ≤ 1   | 15 MB        | `audio/mp3`, `audio/mpeg`, `audio/wav`, `audio/wave`, `audio/x-wav` | 0–20 s   |
| `image_url` | ≤ 1   | 10 MB        | `image/jpeg`, `image/png`, `image/webp`                             | —        |

Every other role is refused: `elements`, `product_id`, `product_images`, `references`, `reference_images`, `end_image_url`, `scene_id`, `scene_image`, `video_urls`, `video_url`, `audio_urls`, `voice_id`. A refused role gets `400 unsupported_option`.

<Callout>
  Each media URL must be an immutable object on 

  `https://cdn.roasos.com`

   that your workspace owns. Any other URL gets 

  `400 reference_media_not_workspace_owned`

  . Refer to 

  [Reference media and uploads](/concepts/reference-media)

   to learn how to put a file there.
</Callout>

## Prompt

* Limit 5,000 characters. No wrapper is added; the prompt is sent verbatim.
* Keep it short and physical: "a woman whispering to the microphone".
* Describe the motion of the image, not the words; the audio carries the words.
* Add one small camera move at most.

## Not exposed

These catalog entries describe omitted inputs, pinned values and source constraints. They do not imply that the provider accepts every listed field.

* `guidance_scale` — pinned to `above 20; fal accepts 1-50`.
* `image_url` — pinned to `required here; fal allows a prompt-only audio-to-video call`.

## Result

The result kind is `lipsync`. Always present: `url`.

```json
{
  "data": {
    "id": "gen_…",
    "kind": "lipsync",
    "model": "ltx-lipsync",
    "status": "completed",
    "result": {
      "url": "https://cdn.roasos.com/workspaces/ws_01/result"
    }
  }
}
```

The files are immutable objects on `https://cdn.roasos.com`. A result URL is a valid media input for your next request.

## Example

The three steps are always the same: quote, run, poll.

<CodeBlockTabs defaultValue="cURL">
  <CodeBlockTabsList>
    <CodeBlockTabsTrigger value="cURL">
      cURL
    </CodeBlockTabsTrigger>

    <CodeBlockTabsTrigger value="JavaScript">
      JavaScript
    </CodeBlockTabsTrigger>

    <CodeBlockTabsTrigger value="Python">
      Python
    </CodeBlockTabsTrigger>
  </CodeBlockTabsList>

  <CodeBlockTab value="cURL">
    ```bash
    # 1. Quote. Nothing is spent.
    curl -X POST https://api.roasos.com/v1/lipsync/ltx-lipsync \
      -H "Authorization: Bearer roasos_sk_live_..." \
      -H "Idempotency-Key: 0f1c9e2a-ltx-lipsync-0001" \
      -H "Content-Type: application/json" \
      -d '{"quote_only":true,"audio_url":"https://cdn.roasos.com/workspaces/ws_01/uploads/audio_url.mp3","image_url":"https://cdn.roasos.com/workspaces/ws_01/uploads/image_url.png"}'
    # 200 { "data": { "kind": "quote", "quote_id": "q_7Hk...", "credits": 12, "expires_at": "...",
    #        "confirmation": { "model": "ltx-lipsync", "example": "10s" } } }

    # 2. Run. Same body, same Idempotency-Key, quote_id in place of quote_only.
    curl -X POST https://api.roasos.com/v1/lipsync/ltx-lipsync \
      -H "Authorization: Bearer roasos_sk_live_..." \
      -H "Idempotency-Key: 0f1c9e2a-ltx-lipsync-0001" \
      -H "Content-Type: application/json" \
      -d '{"quote_id":"q_7Hk...","audio_url":"https://cdn.roasos.com/workspaces/ws_01/uploads/audio_url.mp3","image_url":"https://cdn.roasos.com/workspaces/ws_01/uploads/image_url.png"}'
    # 201 { "data": { "id": "gen_...", "status": "queued", "credits_reserved": 12 } }

    # 3. Poll, then read the result.
    curl https://api.roasos.com/v1/jobs/gen_.../status -H "Authorization: Bearer roasos_sk_live_..."
    curl https://api.roasos.com/v1/jobs/gen_.../result -H "Authorization: Bearer roasos_sk_live_..."
    ```
  </CodeBlockTab>

  <CodeBlockTab value="JavaScript">
    ```javascript
    const key = process.env.ROASOS_API_KEY;
    const url = "https://api.roasos.com/v1/lipsync/ltx-lipsync";
    const idempotencyKey = "0f1c9e2a-ltx-lipsync-0001";
    const input = {
      "audio_url": "https://cdn.roasos.com/workspaces/ws_01/uploads/audio_url.mp3",
      "image_url": "https://cdn.roasos.com/workspaces/ws_01/uploads/image_url.png"
    };

    const post = (payload) =>
      fetch(url, {
        method: "POST",
        headers: {
          Authorization: `Bearer ${key}`,
          "Idempotency-Key": idempotencyKey,
          "Content-Type": "application/json",
        },
        body: JSON.stringify(payload),
      }).then((response) => response.json());

    // 1. Quote. Nothing is spent.
    const quote = await post({ quote_only: true, ...input });
    console.log(quote.data.credits);

    // 2. Run.
    const job = await post({ quote_id: quote.data.quote_id, ...input });

    // 3. Poll, then read the result.
    let status = "queued";
    while (status !== "completed" && status !== "failed" && status !== "canceled") {
      await new Promise((done) => setTimeout(done, 3000));
      const poll = await fetch(`${url.split("/v1")[0]}/v1/jobs/${job.data.id}/status`, {
        headers: { Authorization: `Bearer ${key}` },
      }).then((response) => response.json());
      status = poll.data.status;
    }

    const result = await fetch(`${url.split("/v1")[0]}/v1/jobs/${job.data.id}/result`, {
      headers: { Authorization: `Bearer ${key}` },
    }).then((response) => response.json());
    console.log(result.data.result);
    ```
  </CodeBlockTab>

  <CodeBlockTab value="Python">
    ```python
    import os, time, requests

    key = os.environ["ROASOS_API_KEY"]
    url = "https://api.roasos.com/v1/lipsync/ltx-lipsync"
    headers = {
        "Authorization": f"Bearer {key}",
        "Idempotency-Key": "0f1c9e2a-ltx-lipsync-0001",
    }
    payload = {
        "audio_url": "https://cdn.roasos.com/workspaces/ws_01/uploads/audio_url.mp3",
        "image_url": "https://cdn.roasos.com/workspaces/ws_01/uploads/image_url.png"
    }

    # 1. Quote. Nothing is spent.
    quote = requests.post(url, headers=headers, json={"quote_only": True, **payload}).json()
    print(quote["data"]["credits"])

    # 2. Run.
    job = requests.post(url, headers=headers, json={"quote_id": quote["data"]["quote_id"], **payload}).json()
    job_id = job["data"]["id"]

    # 3. Poll, then read the result.
    jobs = "https://api.roasos.com/v1/jobs"
    status = "queued"
    while status not in ("completed", "failed", "canceled"):
        time.sleep(3)
        status = requests.get(f"{jobs}/{job_id}/status", headers=headers).json()["data"]["status"]

    result = requests.get(f"{jobs}/{job_id}/result", headers=headers).json()
    print(result["data"]["result"])
    ```
  </CodeBlockTab>
</CodeBlockTabs>

## The deprecated path

`POST /v1/generations` still reaches this model for one minor version. It is deprecated. This is how it maps:

The endpoint is `POST /v1/lipsync/ltx-lipsync` with `image_url` (or `avatar_id`) and `audio_url`, plus the optional `prompt`, `guidance_scale` and `aspect_ratio`.

The deprecated alias is `POST /v1/generations` `{ "type": "lipsync", "model": "ltx-lipsync", "options": { "image": "<cdn url>", "audio_url": "<cdn url>", "aspect_ratio": "9:16" } }`. On the alias the prompt is the top-level `prompt` field, `guidance_scale` is not reachable, and `avatar_id` is not accepted.

## See also

* [`llms.txt` for this model](https://docs.roasos.com/models/lipsync/ltx-lipsync/llms.txt) — the same facts as one plain-text file for an agent.
* `GET https://api.roasos.com/v1/catalog/ltx-lipsync` — the machine-readable form: enums, defaults, limits and prices. Refer to the [API reference](/api-reference/overview).
* [Jobs](/concepts/jobs) — how to poll a job and read its result.
* Provider endpoints: `fal-ai/ltx-2.3/audio-to-video`.