LTX-2.5 | LTX Documentation

LTX-2.5 comes in two variants: ltx-2-5-fast for speed and low cost, and ltx-2-5-pro for higher fidelity. Both produce video up to 4K in 16:9, 9:16, 1:1, 3:2, and 2:3.

LTX-2.5 improves every stage of generation on a stronger foundation: a Diffusion Video Decoder with industry-leading pixel quality, higher fidelity, native multi-shot scenes, and a better distilled model.

Native multi-shot means a single generation can produce multiple connected shots, holding character, scene, lighting, visual style, and voice consistent across cuts.

Supported endpoints

Endpoint	ltx-2-5-fast	ltx-2-5-pro
text-to-video	✓	✓
image-to-video	✓	✓
audio-to-video	✓	✓
retake	—	—
extend	—	—

Both variants accept camera_motion, generate_audio: false for silent video, last_frame_uri on image-to-video and audio-to-video, and automatic duration.

Support matrix

Resolutions, FPS values, and duration options supported by each variant.

Duration applies to text-to-video and image-to-video only. For audio-to-video, output length follows your input audio — see maximum input audio length on the API reference.

Model	Resolution	FPS	Duration (seconds)
ltx-2-5-fast	720p	24, 25	6, 8, 10, 12, 14, 16, 18, 20
	720p	48, 50	6, 8, 10
	1080p	24, 25	6, 8, 10, 12, 14, 16, 18, 20
	1080p	48, 50	6, 8, 10
	1440p	24, 25, 48, 50	6, 8, 10
	4K	24, 25, 48, 50	6, 8, 10
ltx-2-5-pro	720p	24, 25, 48, 50	6, 8, 10
	1080p	24, 25, 48, 50	6, 8, 10
	1440p	24, 25, 48, 50	6, 8, 10
	4K	24, 25, 48, 50	6, 8, 10

Resolutions

Resolution	16:9 (landscape)	9:16 (portrait)	1:1 (square)	3:2 (landscape)	2:3 (portrait)
720p	`1280x720`	`720x1280`	`720x720`	`1080x720`	`720x1080`
1080p	`1920x1080`	`1080x1920`	`1080x1080`	`1620x1080`	`1080x1620`
1440p	`2560x1440`	`1440x2560`	`1440x1440`	`2160x1440`	`1440x2160`
4K	`3840x2160`	`2160x3840`	`2160x2160`	`3240x2160`	`2160x3240`

Automatic duration

Send "duration": null and the model picks the length itself, from your prompt. Use it when the prompt describes the shot rather than a fixed slot — a one-line action stays short, a multi-shot sequence runs longer.

Available on ltx-2-5-fast and ltx-2-5-pro for text-to-video and image-to-video.

Send duration with a value of null. The field is still required — leaving it out returns duration is required.

Text-to-video with automatic duration

curl -X POST https://api.ltx.io/v2/text-to-video \
  -H "Authorization: Bearer $LTX_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "ltx-2-5-fast",
    "prompt": "A lighthouse keeper climbs the stairs, then the beam sweeps out over the water",
    "duration": null,
    "resolution": "1280x720",
    "fps": 24
  }'

The result never exceeds the longest duration available for your resolution and frame rate in the table above.

Billing

You are charged for the video you actually get, at the usual per-second rate.

On a prepaid account, credits are held against the longest duration your resolution and frame rate allow, because the length is not known until generation finishes. The unused remainder is released when the job completes. Your balance therefore has to cover that maximum up front — a request that would have produced 6 seconds is still declined if you cannot cover 20 on ltx-2-5-fast, or 10 on ltx-2-5-pro. Postpaid accounts hold nothing and are invoiced for the generated length.

Automatic duration cannot be combined with last_frame_uri on image-to-video. A last frame fixes where the clip has to end, which requires a known length.