LTX-2 19B API

Introduction

LTX-2 19B Video extend continues a clip you already have. Send it as video_url with a prompt for what happens next. The final frame of your clip becomes the opening frame of a new LTX-2 19B image-to-video shot of 5 to 20 seconds, and the two are joined into one MP4: your original first, then the continuation, with the repeated seam frame removed. The new segment also comes back as its own file, so you can keep extending or edit the pieces separately.

Key features

Continuity comes from the last frame. Wardrobe, set, light and where everyone stands carry over because the new segment literally starts on your final frame. Motion does not carry over the same way: the model sees one still, not the whole clip, so describe the movement you want to continue instead of assuming it will keep its speed or direction.

One file back, plus the new piece on its own. The joined MP4 keeps your clip’s frame rate and its framing, with no black bars. To line the seam up, the picture may be trimmed or adjusted by a few percent at the edges. If the model returns a noticeably different shape, the new segment is scaled to fill your frame and centered, cropping what spills over. The file is encoded as H.264 MP4 with AAC sound. Every new segment comes with a stereo soundtrack generated in the same pass, and there is no switch to turn it off. The sound of your source stays, and the two are blended over a short crossfade at the seam so the audio carries across without a hard cut. The second asset in the output is the new segment alone, ready for another extend or for an editor.

Everything else is LTX-2 19B image-to-video.

Request parameters

Pricing

Prices are in credits, the same credits you use on the website (1 credit = $0.01). The hold is taken when the task is accepted and settled to the actual charge when it finishes; failed tasks are refunded.

Each task is rounded up to whole credits, so one run at the lowest tier costs 11 credits for a 5-second clip ($0.11).

For an exact number before you run, send the same body to POST /jobs/quote.

Use cases

Lengthen a shot that ended too early: a product turntable that stops before the label faces camera, or a walk that cuts before the subject reaches the door. Extend it by a few seconds and describe only the remaining motion.

Build a longer sequence step by step. Because every step starts from a single frame, watch each seam before stacking the next one.

Prompt guide & pro tips

Describe the next beat, not the whole scene. The frame already fixes who and where; spend the prompt on the action that follows, the camera move and the sound, and end it with an "Audio:" line naming two or three sounds. Repeat the camera language your clip ended on, such as a slow push in or a locked shot, so the seam reads as one take.

Trim before you extend. The last frame is the only picture the model sees, so a blurred, mid-cut or heavily compressed ending carries straight into the continuation. Cut your source on a clean, sharp frame first. Sources of up to 60 seconds are accepted as MP4, MOV or WebM.

Keep the resolution consistent. The resolution only decides how sharp the new segment is generated, so a lower setting makes the new part look softer than the original.

API quick start

Call the LTX-2 19B API in three steps

1. Create an API key. Sign in to PopNow and create a key in the API console. Keys start with sk-popnow- and use the same credits as the website.
2. Send the request. POST /jobs/createTask with model lightricks/ltx-2-19b/video-extend and an input object that follows the parameter table. The response returns a task ID straight away.
3. Get the result. Poll GET /jobs/recordInfo with the task ID, or pass a callBackUrl and we post the result to it. Download the output links when the task succeeds.

# 1. Create the task. Keep the Idempotency-Key if you retry after a network error.
export IDEMPOTENCY_KEY="$(uuidgen)"
curl -X POST https://api.popnow.ai/api/v1/jobs/createTask \
  -H "Authorization: Bearer $POPNOW_API_KEY" \
  -H "Content-Type: application/json" \
  -H "Idempotency-Key: $IDEMPOTENCY_KEY" \
  -d '{
  "model": "lightricks/ltx-2-19b/video-extend",
  "input": {
    "prompt": "A slow aerial shot drifting over a misty pine forest at sunrise",
    "video_url": "https://media.popnow.ai/effects/flower-bloom-1abd6efb.mp4",
    "resolution": "720p",
    "duration_seconds": 5
  }
}'

# 2. Copy data.taskId from the response, then poll until state is succeeded, failed, canceled or expired.
TASK_ID="TASK_ID_FROM_RESPONSE"
curl "https://api.popnow.ai/api/v1/jobs/recordInfo?taskId=$TASK_ID" \
  -H "Authorization: Bearer $POPNOW_API_KEY"

Replace the prompt and any links with your own. The API tab has the response, polling and callback reference.

LTX-2 19B API questions

All LTX models

LTX 2.5 reaches 2K and 4K for the same 20-second length; LTX-2 19B is the cheaper, open model with clip extension.

• LTX 2.5 APILong 20-second takes up to 4K with a soundtrackFrom 68 credits for a 5-second clip
• LTX-2.3 LoRA APILTX-2.3 clips with stereo sound and your own LoRAsFrom 18 credits for a 5-second clip
• LTX-2 19B API20-second clips with voices, music and effectsFrom 11 credits for a 5-second clip
• LTX-2 19B LoRA APILTX-2 clips with sound and your own LoRA stylesFrom 14 credits for a 5-second clip

Other video APIs

• MiniMax H3 APIExpressive clips with audio, up to 2KFrom 28 credits for a 5-second clip
• Seedance 2.5 APIByteDance's newest: 30-second clips with native audioFrom 56 credits for a 5-second clip
• Kling 3.0 API4K clips, multi-shot cuts and motion controlFrom 51 credits for a 5-second clip
• Vidu Q4 Preview APIUp to 4K clips with sound and spoken dialogueFrom 34 credits for a 5-second clip
• Wan 3.0 APIUp to 30-second clips with synced audioFrom 34 credits for a 5-second clip
• Kling O3 APIKling’s unified model: create, animate, reference and edit up to 4KFrom 51 credits for a 5-second clip

More about LTX-2 19B

Try it

LTX-2 19B AI Video Generator onlineCreate videos with LTX-2 19B in PopNow

Docs

LTX-2 19B model ID and input schema in the API docsPopNow API quickstart: your first request in five minutesImage to video guide for the PopNow APIWebhooks: get LTX-2 19B results without polling