LTX Lipsync

Endpoint

POST https://api.roasos.com/v1/lipsync/ltx-lipsync

Send your API key as a bearer token. The key needs the scope api:write. Every paid request also needs an Idempotency-Key header.

The envelope fields quote_only, quote_id, webhook_url and wait_timeout_seconds behave the same on each model endpoint. Refer to Jobs and Quotes and credits.

Good at

Short social cut-downs of 2 to 10 seconds from one image and one audio file. The prompt describes how the image moves ("a woman whispering to the microphone"). Choose it when the take is short and speed matters. It does not re-lip an existing video (use /v1/lipsync/veed-lipsync-v2) and it does not hold identity over a long take (use /v1/lipsync/kling-avatar-v2-pro when it ships). Audio limit: fal states 2–20 s and "pro models support a maximum of 10 seconds". TBD: which limit applies (spec open question 1); keep the audio at 10 s or shorter.

Pricing

The unit is one second. Pricing key: ltx-lipsync.

The credits come from the roasOS pricing table. No other field changes the price. To get the exact price of your request, send it with quote_only: true first.

Modes

• image-audio-to-video

Provider endpoints: fal-ai/ltx-2.3/audio-to-video.

Request fields

The schema is strict. A field that is not in this table gets 400 unsupported_option. The field names are the roasOS role names. One role has one name in every family.

Media

This endpoint accepts these media roles:

• avatar_id — identity; the saved character reference sheet, with a derived portrait only where the model requires a single face or source frame
• image_url — first frame (or the single source image)
• audio_url — the driving audio track

Every other role is refused: elements, product_id, product_images, references, reference_images, end_image_url, scene_id, scene_image, video_urls, video_url, audio_urls, voice_id. A refused role gets 400 unsupported_option.

Prompt

• Limit 5,000 characters. No wrapper is added; the prompt is sent verbatim.
• Keep it short and physical: "a woman whispering to the microphone".
• Describe the motion of the image, not the words; the audio carries the words.
• Add one small camera move at most.

Not exposed

These catalog entries describe omitted inputs, pinned values and source constraints. They do not imply that the provider accepts every listed field.

• guidance_scale — pinned to above 20; fal accepts 1-50.
• image_url — pinned to required here; fal allows a prompt-only audio-to-video call.

Result

The result kind is lipsync. Always present: url.

{
  "data": {
    "id": "gen_…",
    "kind": "lipsync",
    "model": "ltx-lipsync",
    "status": "completed",
    "result": {
      "url": "https://cdn.roasos.com/workspaces/ws_01/result"
    }
  }
}

The files are immutable objects on https://cdn.roasos.com. A result URL is a valid media input for your next request.

Example

The three steps are always the same: quote, run, poll.

# 1. Quote. Nothing is spent.
curl -X POST https://api.roasos.com/v1/lipsync/ltx-lipsync \
  -H "Authorization: Bearer roasos_sk_live_..." \
  -H "Idempotency-Key: 0f1c9e2a-ltx-lipsync-0001" \
  -H "Content-Type: application/json" \
  -d '{"quote_only":true,"audio_url":"https://cdn.roasos.com/workspaces/ws_01/uploads/audio_url.mp3","image_url":"https://cdn.roasos.com/workspaces/ws_01/uploads/image_url.png"}'
# 200 { "data": { "kind": "quote", "quote_id": "q_7Hk...", "credits": 12, "expires_at": "...",
#        "confirmation": { "model": "ltx-lipsync", "example": "10s" } } }

# 2. Run. Same body, same Idempotency-Key, quote_id in place of quote_only.
curl -X POST https://api.roasos.com/v1/lipsync/ltx-lipsync \
  -H "Authorization: Bearer roasos_sk_live_..." \
  -H "Idempotency-Key: 0f1c9e2a-ltx-lipsync-0001" \
  -H "Content-Type: application/json" \
  -d '{"quote_id":"q_7Hk...","audio_url":"https://cdn.roasos.com/workspaces/ws_01/uploads/audio_url.mp3","image_url":"https://cdn.roasos.com/workspaces/ws_01/uploads/image_url.png"}'
# 201 { "data": { "id": "gen_...", "status": "queued", "credits_reserved": 12 } }

# 3. Poll, then read the result.
curl https://api.roasos.com/v1/jobs/gen_.../status -H "Authorization: Bearer roasos_sk_live_..."
curl https://api.roasos.com/v1/jobs/gen_.../result -H "Authorization: Bearer roasos_sk_live_..."

The deprecated path

POST /v1/generations still reaches this model for one minor version. It is deprecated. This is how it maps:

The endpoint is POST /v1/lipsync/ltx-lipsync with image_url (or avatar_id) and audio_url, plus the optional prompt, guidance_scale and aspect_ratio.

The deprecated alias is POST /v1/generations { "type": "lipsync", "model": "ltx-lipsync", "options": { "image": "<cdn url>", "audio_url": "<cdn url>", "aspect_ratio": "9:16" } }. On the alias the prompt is the top-level prompt field, guidance_scale is not reachable, and avatar_id is not accepted.

See also

• llms.txt for this model — the same facts as one plain-text file for an agent.
• GET https://api.roasos.com/v1/catalog/ltx-lipsync — the machine-readable form: enums, defaults, limits and prices. Refer to the API reference.
• Jobs — how to poll a job and read its result.
• Provider endpoints: fal-ai/ltx-2.3/audio-to-video.