Ltx 2.3 Quality

POST/v1/run

Ltx 2.3 Quality Extend Video by Lightricks - AI-powered video editing and transformation. Apply style transfer, motion control, lip-sync, and visual effects to existing videos with natural language instructions.

Request body

Submit an async generation request. The model field selects the model; other fields are model-specific input parameters.

stringmodelrequired

Model identifier. Set to lightricks/ltx-2.3-quality/extend-video.

Default: lightricks/ltx-2.3-quality/extend-video

stringpromptrequired

The prompt describing how the video should continue.

Optional<string>end_image

Optional keyframe image for the far end of the extension: the final frame for forward extension, or the new first frame for backward extension.

Optional<string>video

The URL of the video to extend.

Optional<string>resolution

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.

Allowed values: auto, square_hd, square, portrait_4_3, portrait_16_9, landscape_4_3, landscape_16_9

Default: auto

Optional<boolean>generate_audio

Whether 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: true

Optional<number>guidance_scale

Classifier-free guidance scale. The default is tuned for fast, high-quality generation.

Range: 1 to 20

Default: 1

Optional<integer>num_inference_steps

Number of inference steps. Defaults to 15 and can be increased up to 30.

Range: 8 to 30

Default: 15

Optional<integer>seed

Random seed for reproducibility. If None, a random seed is chosen.

Optional<integer>num_context_frames

The 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.

Range: 9 to 121

Default: 25

Optional<string>video_write_mode

The write mode of the generated video.

Allowed values: fast, balanced, small

Default: balanced

Optional<string>video_quality

The quality preset of the generated video.

Allowed values: low, medium, high, maximum

Default: high

Optional<boolean>match_input_fps

When 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: true

Optional<number>video_strength

Conditioning 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.

Range: 0 to 1

Default: 1

Optional<integer>num_frames

The 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).

Range: 9 to 481

Default: 121

Optional<number>frames_per_second

Frames per second of the generated video.

Range: 1 to 60

Default: 24

Optional<string>extend_direction

Direction to extend the video. 'forward' continues from the end of the video, 'backward' generates a new beginning.

Allowed values: forward, backward

Default: forward

Optional<number>end_image_strength

Conditioning strength of the optional end keyframe. 1.0 = exact match, lower = more freedom for the model.

Range: 0 to 1

Default: 1

Response Schema

The submit endpoint returns a run response. If its status is pending or running, poll GET /v1/run/{id} with the returned opaque ID until it reaches a terminal state.

stringidrequired

Opaque SandBase run identifier. Use it exactly as returned; no prefix is guaranteed.

stringstatusrequired

Current public run status.

Allowed values: pending, running, completed, failed, timeout

Optional<string>model

Public SandBase model name used for this run.

Optional<array<object>>outputs

Present only for completed runs. Each object is capability-specific; inspect the selected model schema for its fields.

Optional<object>error

Present only for failed or timeout runs. Contains a public error type and sanitized message.

Optional<string>error.type

Stable public error category.

Optional<string>error.message

Sanitized error message safe to show to clients.

Optional<object>usage

Usage details when available.

Model capabilities

array<string>capability_tagsrequired

Capabilities declared by the model registry.

Default: video-to-video

stringexecution_moderequired

Execution mode declared by the model registry.

Default: async

# 1. Submit a generation request
curl -X POST https://api.sandbase.ai/v1/run \
  -H "Authorization: Bearer $SANDBASE_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
  "model": "lightricks/ltx-2.3-quality/extend-video",
  "prompt": "Continue the scene naturally, maintaining the same style and motion.",
  "video": "https://v3b.fal.media/files/b/0a8824b1/sdm0KfmenrlywesfzY1Y1_if6euPp1.mp4"
}'

# 2. If the response is still running, poll the returned id
curl https://api.sandbase.ai/v1/run/f3d2e8a1-7c4b-4a12-9d2e-123456789abc \
  -H "Authorization: Bearer $SANDBASE_API_KEY"

Response202 Accepted

{
  "id": "f3d2e8a1-7c4b-4a12-9d2e-123456789abc",
  "model": "lightricks/ltx-2.3-quality/extend-video",
  "status": "running"
}