Extend a video forward or backward from a text prompt.
The client provides a convenient way to interact with the model API.
npm install --save @fal-ai/clientThe @fal-ai/serverless-client package has been deprecated in favor of @fal-ai/client. Install the new package and update your imports — see client setup.
Set FAL_KEY as an environment variable in your runtime.
export FAL_KEY="YOUR_API_KEY"The client API handles the API submit protocol. It will handle the request status updates and return the result when the request is completed.
import { fal } from "@fal-ai/client";
const result = await fal.subscribe("fal-ai/ltx-2.3-quality/extend-video", {
input: {
prompt: "Continue the scene naturally, maintaining the same style and motion.",
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);The API uses an API Key for authentication. It is recommended you set the FAL_KEY environment variable in your runtime when possible.
import { fal } from "@fal-ai/client";
fal.config({
credentials: "YOUR_FAL_KEY"
});When running code on the client-side (e.g. in a browser, mobile app or GUI applications), make sure to not expose your FAL_KEY. Instead, use a server-side proxy to make requests to the API. For more information, check out our server-side integration guide.
The client API provides a convenient way to submit requests to the model.
import { fal } from "@fal-ai/client";
const { request_id } = await fal.queue.submit("fal-ai/ltx-2.3-quality/extend-video", {
input: {
prompt: "Continue the scene naturally, maintaining the same style and motion.",
video_url: "https://v3b.fal.media/files/b/0a8824b1/sdm0KfmenrlywesfzY1Y1_if6euPp1.mp4"
},
webhookUrl: "https://optional.webhook.url/for/results",
});You can fetch the status of a request to check if it is completed or still in progress.
import { fal } from "@fal-ai/client";
const status = await fal.queue.status("fal-ai/ltx-2.3-quality/extend-video", {
requestId: "764cabcf-b745-4b3e-ae38-1200304cf45b",
logs: true,
});Once the request is completed, you can fetch the result. See the Output Schema for the expected result format.
import { fal } from "@fal-ai/client";
const result = await fal.queue.result("fal-ai/ltx-2.3-quality/extend-video", {
requestId: "764cabcf-b745-4b3e-ae38-1200304cf45b"
});
console.log(result.data);
console.log(result.requestId);Some attributes in the API accept file URLs as input. Whenever that's the case you can pass your own URL or a Base64 data URI.
You can pass a Base64 data URI as a file input. The API will handle the file decoding for you. Keep in mind that for large files, this alternative although convenient can impact the request performance.
You can also pass your own URLs as long as they are publicly accessible. Be aware that some hosts might block cross-site requests, rate-limit, or consider the request as a bot.
We provide a convenient file storage that allows you to upload files and use them in your requests. You can upload files using the client API and use the returned URL in your requests.
import { fal } from "@fal-ai/client";
const file = new File(["Hello, World!"], "hello.txt", { type: "text/plain" });
const url = await fal.storage.upload(file);The client will auto-upload the file for you if you pass a binary object (e.g. File, Data).
Read more about file handling in our file upload guide.
prompt string* requiredThe prompt describing how the video should continue.
video_url string* requiredThe URL of the video to extend.
extend_direction ExtendDirectionEnumDirection to extend the video. 'forward' continues from the end of the video, 'backward' generates a new beginning. Default value: "forward"
Possible enum values: forward, backward
num_frames integerThe number of frames to generate for the extension segment, including num_context_frames of overlap with the source video. The new content adds approximately (num_frames - num_context_frames) / frames_per_second seconds. The stable generation budget caps the resolution x frames volume: at 24 fps roughly 20s at 480p-class, 11s at 720p-class and 5s at 1080p-class; a request above the budget returns a 422 (lower num_frames or use a smaller resolution). Default value: 121
num_context_frames integerThe number of source frames used as context/overlap for the extension. Snapped down to the LTX temporal grid (8k+1) and clamped to the frames available in the source video. Default value: 25
end_image_url stringOptional keyframe image for the far end of the extension: the final frame for forward extension, or the new first frame for backward extension.
end_image_strength floatConditioning strength of the optional end keyframe. 1.0 = exact match, lower = more freedom for the model. Default value: 1
The size of the generated video. 'auto' follows the source video size/aspect up to the LTX limits; the source is scaled to the final size in the stitched output. Sizes are 32px-aligned (e.g. 1920x1080 is delivered as 1888x1056). Higher resolutions reduce the maximum stable extension length; lower resolutions can run longer. Default value: auto
Possible enum values: auto, square_hd, square, portrait_4_3, portrait_16_9, landscape_4_3, landscape_16_9
Note: For custom image sizes, you can pass the width and height as an object:
"image_size": {
"width": 1280,
"height": 720
}match_input_fps booleanWhen enabled, the output FPS matches the source video's FPS (rounded to an integer and clamped to the supported range) instead of frames_per_second. Default value: true
frames_per_second floatFrames per second of the generated video. Default value: 24
video_strength floatConditioning strength of the source context frames. 1.0 keeps the overlap locked to the source for a seamless transition; lower values give the model more freedom. Default value: 1
num_inference_steps integerNumber of inference steps. Defaults to 15 and can be increased up to 30. Default value: 15
guidance_scale floatClassifier-free guidance scale. The default is tuned for fast, high-quality generation. Default value: 1
generate_audio booleanWhether to generate new audio for the extension segment (crossfaded with the source audio at the seam). When disabled, the source video's own audio track is preserved and the extension stays silent. Default value: true
negative_prompt stringThe 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"
seed integerRandom seed for reproducibility. If None, a random seed is chosen.
enable_prompt_expansion booleanWhether to enable prompt expansion. Default value: true
enable_safety_checker booleanWhether to enable the safety checker. Default value: true
video_quality VideoQualityEnumThe quality preset of the generated video. Default value: "high"
Possible enum values: low, medium, high, maximum
video_write_mode VideoWriteModeEnumThe write mode of the generated video. Default value: "balanced"
Possible enum values: fast, balanced, small
sync_mode booleanIf True, the media is returned as a data URI inline in the response. Useful for short-lived requests and tests.
{
"prompt": "Continue the scene naturally, maintaining the same style and motion.",
"video_url": "https://v3b.fal.media/files/b/0a8824b1/sdm0KfmenrlywesfzY1Y1_if6euPp1.mp4",
"extend_direction": "forward",
"num_frames": 121,
"num_context_frames": 25,
"end_image_strength": 1,
"resolution": "auto",
"match_input_fps": true,
"frames_per_second": 24,
"video_strength": 1,
"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"
}The generated video.
seed integer* requiredThe seed actually used for generation.
prompt string* requiredThe prompt used for generation (after any expansion).
{
"video": {
"url": "",
"content_type": "image/png",
"file_name": "z9RV14K95DvU.png",
"file_size": 4404019
},
"prompt": ""
}width integerThe width of the generated image. Default value: 512
height integerThe height of the generated image. Default value: 512
url string* requiredThe URL where the file can be downloaded from.
content_type stringThe mime type of the file.
file_name stringThe name of the file. It will be auto-generated if not provided.
file_size integerThe size of the file in bytes.