# Ltx 2.3 Quality

> Generate high-quality video with audio from reference video, text and images using LTX-2.3


## Overview

- **Endpoint**: `https://fal.run/fal-ai/ltx-2.3-quality/reference-video-to-video`
- **Model ID**: `fal-ai/ltx-2.3-quality/reference-video-to-video`
- **Category**: video-to-video
- **Kind**: inference


## Pricing

Your request will cost $0.0024075 per megapixel of generated video data (width × height × frames), rounded up. For example, if you generate a video that is 121 frames long at 1280 × 720, your total generated video is ≈112 MP, and your request will cost $0.270.

For more details, see [fal.ai pricing](https://fal.ai/pricing).

## API Information

This model can be used via our HTTP API or more conveniently via our client libraries.
See the input and output schema below, as well as the usage examples.


### Input Schema

The API accepts the following input parameters:


- **`prompt`** (`string`, _required_):
  The prompt to guide generation.
  - Examples: "A dancer in a flowing red dress against a black backdrop, studio lighting, cinematic."

- **`video_url`** (`string`, _required_):
  The URL of the reference video that supplies motion/structure.
  - Examples: "https://v3b.fal.media/files/b/0a8824b1/sdm0KfmenrlywesfzY1Y1_if6euPp1.mp4"

- **`control_video_url`** (`string`, _optional_):
  Optional pre-computed control video (e.g. an already-rendered depth / edge / pose composite). When provided together with skip_control_preprocess, the built-in control estimation is skipped and this video is used directly as the control signal, resampled to the output resolution and frame count.

- **`skip_control_preprocess`** (`boolean`, _optional_):
  Skip the built-in control estimation (depth / edge / pose) and use control_video_url directly as the control signal. Requires control_video_url; ignored if it is not set. With resolution='auto', the output follows the source video size/aspect up to the LTX limits. Explicit resolutions are honored and 64-aligned so the RGB video and control video stay matched.
  - Default: `false`

- **`preserve_original_video`** (`boolean`, _optional_):
  True video-to-video: the base video_url is used as the generation's starting point, while control_video_url still drives the structure. The amount of the original preserved is controlled by `strength` (denoise): lower `strength` keeps more of the original video's pixels. Requires skip_control_preprocess, video_url and control_video_url. Default off leaves the standard control path unchanged.
  - Default: `false`

- **`image_url`** (`string`, _optional_):
  Optional reference image for style/character anchoring. This is the FIRST-frame keyframe.

- **`mid_image_url`** (`string`, _optional_):
  Optional middle-frame keyframe image. When set, the look/appearance is anchored to this image around the middle of the clip (in addition to image_url at the start), so the appearance follows a moving camera instead of drifting. Requires image_url.

- **`end_image_url`** (`string`, _optional_):
  Optional last-frame keyframe image. When set, the look/appearance is anchored to this image at the end of the clip. Useful for shots where the camera travels to a different place than the start image. Requires image_url.

- **`video_strength`** (`float`, _optional_):
  Video conditioning strength. Lower values give the model more freedom to change the reference video motion/structure. Default value: `0.6`
  - Default: `0.6`
  - Range: `0` to `1`

- **`strength`** (`float`, _optional_):
  Sampler denoise strength for reference-video-to-video. With preserve_original_video on, this is the video-to-video amount: lower values keep more of the original video's pixels (e.g. 0.5 = keep ~50%), 1.0 fully regenerates. Without preserve_original_video it only trims the denoise schedule. Default value: `1`
  - Default: `1`
  - Range: `0` to `1`

- **`num_frames`** (`integer`, _optional_):
  The number of output frames to generate. This IC-LoRA endpoint caps the resolution x frames volume for stability (~150 frames at 720p-class; more at smaller sizes). A request above the budget returns a 422 — reduce num_frames or use a smaller resolution. Default value: `121`
  - Default: `121`
  - Range: `9` to `481`

- **`resolution`** (`ImageSize | Enum`, _optional_):
  The size of the generated video. In direct-control mode (skip_control_preprocess with control_video_url), 'auto' follows the source video size/aspect up to the LTX limits and explicit sizes are honored with 64px alignment. In the built-in control estimation mode, the output stays near the official control workflow size. Higher resolutions reduce the maximum stable frame count; lower resolutions can run longer. Default value: `auto`
  - Default: `"auto"`
  - One of: ImageSize | Enum

- **`frames_per_second`** (`float`, _optional_):
  Frames per second of the generated video. Default value: `24`
  - Default: `24`
  - Range: `1` to `60`

- **`num_inference_steps`** (`integer`, _optional_):
  Number of inference steps. Defaults to 15 and can be increased up to 30. Default value: `15`
  - Default: `15`
  - Range: `8` to `30`

- **`guidance_scale`** (`float`, _optional_):
  Classifier-free guidance scale. The default is tuned for fast, high-quality generation. Default value: `1`
  - Default: `1`
  - Range: `1` to `20`

- **`generate_audio`** (`boolean`, _optional_):
  Whether to include audio in the returned video. When disabled, the final MP4 is returned without an audio track. Default value: `true`
  - Default: `true`

- **`negative_prompt`** (`string`, _optional_):
  The negative prompt to steer generation away from. Default value: `"color distortion, overexposure, static, blurry details, subtitles, style, artwork, painting, frame, still, dim overall tone, worst quality, low quality, JPEG compression artifacts, ugly, mutilated, extra fingers, poorly drawn hands, poorly drawn face, deformed, disfigured, malformed limbs, fused fingers, motionless frame, cluttered background, three legs, crowded background, walking backwards"`
  - Default: `"color distortion, overexposure, static, blurry details, subtitles, style, artwork, painting, frame, still, dim overall tone, worst quality, low quality, JPEG compression artifacts, ugly, mutilated, extra fingers, poorly drawn hands, poorly drawn face, deformed, disfigured, malformed limbs, fused fingers, motionless frame, cluttered background, three legs, crowded background, walking backwards"`

- **`seed`** (`integer`, _optional_):
  Random seed for reproducibility. If None, a random seed is chosen.

- **`enable_prompt_expansion`** (`boolean`, _optional_):
  Whether to enable prompt expansion. Default value: `true`
  - Default: `true`

- **`enable_safety_checker`** (`boolean`, _optional_):
  Whether to enable the safety checker. Default value: `true`
  - Default: `true`

- **`video_quality`** (`VideoQualityEnum`, _optional_):
  The quality preset of the generated video. Default value: `"high"`
  - Default: `"high"`
  - Options: `"low"`, `"medium"`, `"high"`, `"maximum"`

- **`video_write_mode`** (`VideoWriteModeEnum`, _optional_):
  The write mode of the generated video. Default value: `"balanced"`
  - Default: `"balanced"`
  - Options: `"fast"`, `"balanced"`, `"small"`

- **`sync_mode`** (`boolean`, _optional_):
  If True, the media is returned as a data URI inline in the response. Useful for short-lived requests and tests.
  - Default: `false`



**Required Parameters Example**:

```json
{
  "prompt": "A dancer in a flowing red dress against a black backdrop, studio lighting, cinematic.",
  "video_url": "https://v3b.fal.media/files/b/0a8824b1/sdm0KfmenrlywesfzY1Y1_if6euPp1.mp4"
}
```

**Full Example**:

```json
{
  "prompt": "A dancer in a flowing red dress against a black backdrop, studio lighting, cinematic.",
  "video_url": "https://v3b.fal.media/files/b/0a8824b1/sdm0KfmenrlywesfzY1Y1_if6euPp1.mp4",
  "video_strength": 0.6,
  "strength": 1,
  "num_frames": 121,
  "resolution": "auto",
  "frames_per_second": 24,
  "num_inference_steps": 15,
  "guidance_scale": 1,
  "generate_audio": true,
  "negative_prompt": "color distortion, overexposure, static, blurry details, subtitles, style, artwork, painting, frame, still, dim overall tone, worst quality, low quality, JPEG compression artifacts, ugly, mutilated, extra fingers, poorly drawn hands, poorly drawn face, deformed, disfigured, malformed limbs, fused fingers, motionless frame, cluttered background, three legs, crowded background, walking backwards",
  "enable_prompt_expansion": true,
  "enable_safety_checker": true,
  "video_quality": "high",
  "video_write_mode": "balanced"
}
```


### Output Schema

The API returns the following output format:

- **`video`** (`File`, _required_):
  The generated video.

- **`seed`** (`integer`, _required_):
  The seed actually used for generation.

- **`prompt`** (`string`, _required_):
  The prompt used for generation (after any expansion).



**Example Response**:

```json
{
  "video": {
    "url": "",
    "content_type": "image/png",
    "file_name": "z9RV14K95DvU.png",
    "file_size": 4404019
  },
  "prompt": ""
}
```


## Usage Examples

### cURL

```bash
curl --request POST \
  --url https://fal.run/fal-ai/ltx-2.3-quality/reference-video-to-video \
  --header "Authorization: Key $FAL_KEY" \
  --header "Content-Type: application/json" \
  --data '{
     "prompt": "A dancer in a flowing red dress against a black backdrop, studio lighting, cinematic.",
     "video_url": "https://v3b.fal.media/files/b/0a8824b1/sdm0KfmenrlywesfzY1Y1_if6euPp1.mp4"
   }'
```

### Python

Ensure you have the Python client installed:

```bash
pip install fal-client
```

Then use the API client to make requests:

```python
import fal_client

def on_queue_update(update):
    if isinstance(update, fal_client.InProgress):
        for log in update.logs:
           print(log["message"])

result = fal_client.subscribe(
    "fal-ai/ltx-2.3-quality/reference-video-to-video",
    arguments={
        "prompt": "A dancer in a flowing red dress against a black backdrop, studio lighting, cinematic.",
        "video_url": "https://v3b.fal.media/files/b/0a8824b1/sdm0KfmenrlywesfzY1Y1_if6euPp1.mp4"
    },
    with_logs=True,
    on_queue_update=on_queue_update,
)
print(result)
```

### JavaScript

Ensure you have the JavaScript client installed:

```bash
npm install --save @fal-ai/client
```

Then use the API client to make requests:

```javascript
import { fal } from "@fal-ai/client";

const result = await fal.subscribe("fal-ai/ltx-2.3-quality/reference-video-to-video", {
  input: {
    prompt: "A dancer in a flowing red dress against a black backdrop, studio lighting, cinematic.",
    video_url: "https://v3b.fal.media/files/b/0a8824b1/sdm0KfmenrlywesfzY1Y1_if6euPp1.mp4"
  },
  logs: true,
  onQueueUpdate: (update) => {
    if (update.status === "IN_PROGRESS") {
      update.logs.map((log) => log.message).forEach(console.log);
    }
  },
});
console.log(result.data);
console.log(result.requestId);
```


## Additional Resources

### Documentation

- [Model Playground](https://fal.ai/models/fal-ai/ltx-2.3-quality/reference-video-to-video)
- [API Documentation](https://fal.ai/models/fal-ai/ltx-2.3-quality/reference-video-to-video/api)
- [OpenAPI Schema](https://fal.ai/api/openapi/queue/openapi.json?endpoint_id=fal-ai/ltx-2.3-quality/reference-video-to-video)

### fal.ai Platform

- [Platform Documentation](https://fal.ai/docs/documentation)
- [Python Client](https://fal.ai/docs/api-reference/client-libraries/python)
- [JavaScript Client](https://fal.ai/docs/api-reference/client-libraries/javascript)

### Other agent-readable surfaces

This file covers one model. To find anything else:

- [Platform overview](https://fal.ai/llms.txt): Entry points and representative endpoint IDs
- [Documentation index](https://fal.ai/docs/llms.txt): Every documentation page
- [Full documentation text](https://fal.ai/docs/llms-full.txt): The whole documentation inlined
- Any other model: `https://fal.ai/models/<endpoint-id>/llms.txt`