LTX-2.3 Video API

API Reference

Base URL: https://api.ltx.video/v1
Auth: Authorization: Bearer <API_KEY>
Response: MP4 binary (direct download, no polling)

Endpoints

Endpoint	Input	Use
/v1/text-to-video	prompt	Generate video from text
/v1/image-to-video	image_uri + prompt	Animate a still image
/v1/audio-to-video	audio_uri + image_uri + prompt	Lip-sync video from audio + image
/v1/extend	video_uri + prompt	Extend a video at start or end
/v1/retake	video_uri + time range	Regenerate a section of a video

Models

Model	Speed	Quality
ltx-2-3-fast	~17s	Good (use for tests)
ltx-2-3-pro	~30-60s	Best (use for final)

Supported Resolutions

• 1920x1080 (landscape 16:9)
• 1080x1920 (portrait 9:16 — native vertical, trained on vertical data)
• 1440x1080, 4096x2160 (text-to-video only)

audio-to-video only supports: 1920x1080 or 1080x1920

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Quick Examples

Text to Video

curl -X POST "https://api.ltx.video/v1/text-to-video" \
  -H "Authorization: Bearer $LTX_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "prompt": "A man in a navy blue suit sits at a luxury restaurant table...",
    "model": "ltx-2-3-pro",
    "duration": 8,
    "resolution": "1920x1080"
  }' -o output.mp4

Audio to Video (Lip-sync)

curl -X POST "https://api.ltx.video/v1/audio-to-video" \
  -H "Authorization: Bearer $LTX_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "audio_uri": "https://example.com/voice.mp3",
    "image_uri": "https://example.com/portrait.jpg",
    "prompt": "A man speaks directly to camera...",
    "model": "ltx-2-3-pro",
    "resolution": "1920x1080"
  }' -o output.mp4

Python Wrapper

import requests

def ltx_audio_to_video(audio_url, image_url, prompt, api_key,
                        model="ltx-2-3-pro", resolution="1920x1080",
                        output_path="output.mp4"):
    r = requests.post(
        "https://api.ltx.video/v1/audio-to-video",
        headers={"Authorization": f"Bearer {api_key}",
                 "Content-Type": "application/json"},
        json={"audio_uri": audio_url, "image_uri": image_url,
              "prompt": prompt, "model": model, "resolution": resolution},
        timeout=300, stream=True
    )
    if r.status_code != 200:
        raise RuntimeError(f"LTX error {r.status_code}: {r.text}")
    with open(output_path, "wb") as f:
        for chunk in r.iter_content(8192): f.write(chunk)
    return output_path

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⚠️ Critical Rules (learned from experience)

File Hosting

• URLs must be HTTPS — HTTP is rejected
• Files must return correct MIME type (not application/octet-stream)
• uguu.se works: upload with curl -F "files[]=@file.mp3" https://uguu.se/upload
• Audio: upload as MP3 (not WAV) → uguu returns audio/mpeg ✅
• 4K images fail → resize to 1920x1080 before uploading

# Upload MP3 to uguu.se
AUDIO_URL=$(curl -s -F "files[]=@audio.mp3" "https://uguu.se/upload" | \
  python3 -c "import sys,json; print(json.load(sys.stdin)['files'][0]['url'])")

# Upload image
IMAGE_URL=$(curl -s -F "files[]=@portrait.jpg" "https://uguu.se/upload" | \
  python3 -c "import sys,json; print(json.load(sys.stdin)['files'][0]['url'])")

Image Size Limit

# Resize large images before upload
ffmpeg -y -i input_4k.png -vf "scale=1920:1080" output_1080.jpg

Face Consistency

• Avoid prompts where the character looks down — breaks face consistency
• Keep head level and gaze forward throughout
• Place objects already in frame instead of having character reach below frame

Last Frame

• LTX does not support first+last frame natively
• Workaround: generate clip A, generate clip B, then use /v1/extend to chain them

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Prompting Guide (LTX-2.3)

LTX-2.3 has a much stronger text connector. Specificity wins.

1. Use Verbs, Not Nouns

❌ "A dramatic portrait of a man standing"
✅ "A man stands on a rooftop. His coat flaps in the wind. He adjusts his collar and steps forward as the camera tracks right."

2. Block the Scene Like a Director

• Specify left vs right, foreground vs background
• Describe who moves, what moves, how they move, what the camera does
• Spatial relationships are now respected

3. Describe Audio Explicitly (for text-to-video)

• Name the type of sound: dialogue, ambient, music
• Specify tone and intensity
• Example: "His voice is clear and warm. Restaurant ambient sound softly in the background."

4. Avoid Static Photo-Like Prompts

• If the prompt reads like a still image → the output behaves like one
• Add wind, motion, breathing, gestures, camera movement

5. Describe Texture and Material

• Hair, fabric, surface finish, lighting fall-off
• "Individual hair strands visible in the backlight" → now renders correctly

6. Portrait (9:16) Native

• resolution: "1080x1920" → trained on vertical data
• Frame for vertical intentionally, don't treat as cropped landscape

7. Complex Shots Work Now

• Layer multiple actions: "He picks up the banana, raises it to his ear, and smirks"
• Combine character performance + environment + camera motion

Lip-Sync Prompt Template

A [description of person] sits/stands [location]. He/she speaks directly 
to camera, lips moving in perfect sync with his/her voice. [Gesture details]. 
Head stays level and gaze remains locked on camera throughout. 
[Environment description softly blurred in background]. 
[Lighting]. [Camera: holds steady at eye level, front-on].

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ComfyUI Node

Custom nodes for ComfyUI (no manual API calls):

cd ComfyUI/custom_nodes
git clone https://github.com/PauldeLavallaz/comfyui-ltx-node

Nodes: LTX Text to Video, LTX Image to Video, LTX Extend Video
Category: LTX Video

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API Key

Paul's key: stored in ~/clawd/.env as LTX_API_KEY

ltxv_RfSU5hdKJb_g5dwbECZWnilE1P8dJzbavz6niP_0LQJ942ARHIVhrBCfebcytEL1efLVx_63S_PJyWTzicrBcWEkOXfCbGTl8JSzlJJk329MwRViEgOoE2KnE9LIA5t6QSFeBy7DLnTIcX0AZNbV9Jv0TuC7qcq2gV33G6ROhUVUDCuN