# LTX 2.3 Trainer (V2) - Forward Video Extension API

> Trenirinel LTX 2.3 LoRA vaš angluno videosko lungaripen: den les startutno klipo thaj leske lel so avel palal

Sikavel jekh LoRA katar jekh `.zip` trening-klipenca (`training_data_url`) kaj o modelo te šaj te lungarel video palal dino angluno segmento. Thov `conditioning_frames` vaš o lungipe e prefiksosko, thaj aktivisar `with_audio` kaj te lungarel o zvuko kethane e videosa. Rank (8 to 128), paso (100 to 10000), kadro (9 to 121), rezolucija thaj proporcija (16:9, 1:1, 9:16) šaj te aven promenime. Dži duj validation-klipa šaj te aven dikhle, thaj o rezultato si le LoRA pharipen fajlo.

- Model id: `ltx23-trainer-v2/extend-prefix`
- Made by: Lightricks
- Category: Training
- Output: file
- Price: $0.0062 / step (cheapest run $12.40 (12400 API credits))
- Run: `POST https://api.doitong.com/v1/run/ltx23-trainer-v2/extend-prefix`
- Quote: `POST https://api.doitong.com/v1/quote/ltx23-trainer-v2/extend-prefix`
- Docs page: https://doitong.com/rom/developers/models/ltx23-trainer-v2/extend-prefix

## Pricing

Price: **$0.0062 / step**. Billed per training step (`number_of_steps`).

The full example input below costs $12.40 = 12400 API credits (2000 steps × 6.2 API credits).

Prices are the upstream price in USD, paid from the API balance in API credits (1000 API credits = 1 USD). `POST https://api.doitong.com/v1/quote/ltx23-trainer-v2/extend-prefix` with the same JSON body returns the exact price for that input; the quote is exactly what a run charges. Invalid input is never charged and failed or canceled requests are refunded automatically.

## Input parameters

| Parameter | Canonical name | Type | Required | Default | Allowed values / range | Description |
|---|---|---|---|---|---|---|
| `training_data_url` |  | string | yes |  |  | URL vašo `.zip` savo si training-datenca, organizime palal o alosardo training modo. Sako media fajlo šaj te avel les accompanying `.txt` caption jekhetane base name-esa. |
| `rank` |  | enum (integer) | no | `32` | `8`, `16`, `32`, `64`, `128` | LoRA adaptation rank, savo lel maj-baro memory thaj del maj-bari capacity kana vazdel pes. |
| `number_of_steps` |  | integer | no | `2000` | 100 – 10,000 | Sa e training steps-enge gind. |
| `learning_rate` |  | number | no | `0.0002` | 0.000001 – 1 | Optimization learning rate. |
| `number_of_frames` |  | integer | no | `89` | 9 – 121 | Kadro-gind sako training sample-oske. Te del o gind pe 8, o remainder si 1; exempelura si 1, 9, 17, 25, 33, 41, 49, 57, 65, 73, 81, 89, 97. |
| `frame_rate` |  | integer | no | `24` | 8 – 60 | Training-videosko ciljuno kadro rate andro kadro pe sekunda. Native rate vašo LTX-2.3 si 24. |
| `resolution` |  | enum (string) | no | `medium` | `low`, `medium`, `high` | Training rezolucija. Maj-bari rezolucija mangel maj-baro memory. |
| `aspect_ratio` |  | enum (string) | no | `1:1` | `16:9`, `1:1`, `9:16` | Training aspect ratio. |
| `trigger_phrase` |  | string | no | `` |  | LoRA stiloski activation fraza, thovi pes andro captionsko starto andro training. |
| `auto_scale_input` |  | boolean | no | `false` |  | Automatikano video adjustment te jakharel e manglini FPS thaj kadro-gind kana si aktivno; kipo datasets ačhen bi paruvipen. |
| `split_input_into_scenes` |  | boolean | no | `true` |  | Scene splitting videoske save našen durata threshold, aktivno kana si true. |
| `split_input_duration_threshold` |  | number | no | `30` | 1 – 60 | Scene-splitting trigger, sikavdo durata andro sekunda: numa videona maj-bare sar threshold si split-ime. |
| `debug_dataset` |  | boolean | no | `false` |  | Preprocessing inspection modo vašo video, kipo thaj caption proveripen angleder full training run. Kana si aktivno, trainer del processed training dataset andro download-ime archive vašo manušikano dikhipen. |
| `with_audio` |  | boolean | no | `false` |  | Extension mode: false, standardno, pharavel numa o video thaj sikavel pharado rezultato. Trueha, o audio thaj video džan majdur katar jek shared prefix window, thaj sako training thaj validation clip trubul te avel audio track. |
| `audio_normalize` |  | boolean | no | `true` |  | Audio peak normalization te ačharel jekhetareske levelura savore datasetosko. |
| `audio_preserve_pitch` |  | boolean | no | `true` |  | Pitch ačharipen kana audio si adjust-ime te jakharel e video-durata, na triming vaj padding les. |
| `conditioning_frames` |  | integer | no | `9` | 9 – 121 | Ginesko clean-prefix kadronengo, mapimo ande latent `temporal_boundary` sar `(conditioning_frames-1)//8+1`. O prefix lel anglutne pixel-kadro thaj kondicioninel vi audioha `with_audio`; valid gines si 1 modulo 8, sar 9, 17 vaj 25. O clip trubul te avel maj but latent kadro sar kadava boundary vaj te del dromos la continuation keripeske. |
| `validation` |  | array of object {prompt, video_url} | no | `[]` | ≤ 2 items | Validation data vaj forward video extension, dine sar lista entriesenge save promptoha thaj videosa vaj te avel maj dur. |
| `validation[].prompt` |  | string | yes |  |  | Prompto savo si lavdo andro validation. |
| `validation[].video_url` |  | string (video URL) | yes |  | ≥ 1 characters | URL videovoski vaj extension lungo o time axis. |
| `validation_negative_prompt` |  | string | no | `blurry, out of focus, overexposed, underexposed, low contrast, washed out colors, excessive noise, grainy texture, poor lighting, flickering, motion blur, distorted proportions, unnatural skin tones, deformed facial features, asymmetrical face, missing facial features, extra limbs, disfigured hands, wrong hand count, artifacts around text, inconsistent perspective, camera shake, incorrect depth of field, background too sharp, background clutter, distracting reflections, harsh shadows, inconsistent lighting direction, color banding, cartoonish rendering, 3D CGI look, unrealistic materials, uncanny valley effect, incorrect ethnicity, wrong gender, exaggerated expressions, wrong gaze direction, mismatched lip sync, silent or muted audio, distorted voice, robotic voice, echo, background noise, off-sync audio, incorrect dialogue, added dialogue, repetitive speech, jittery movement, awkward pauses, incorrect timing, unnatural transitions, inconsistent framing, tilted camera, flat lighting, inconsistent tone, cinematic oversaturation, stylized filters, or AI artifacts.` |  | Negativno prompto lavdo andro validation, savo lel single-stage preview process. Kaj kadava process približuil distilled production inference duje stage-enca, leski guidance thaj preview kvaliteta si aver finalno rezultatosar. |
| `validation_number_of_frames` |  | integer | no | `89` | 9 – 121 | Kadro-gind sako validation videoske. |
| `validation_frame_rate` |  | integer | no | `24` | 8 – 60 | Ciljuno kadro rate validation videoske, andro kadro pe sekunda; LTX-2.3 si native 24-esa. |
| `validation_resolution` |  | enum (string) | no | `high` | `low`, `medium`, `high` | Rezolucija savi si lavdi andro validation. |
| `validation_aspect_ratio` |  | enum (string) | no | `1:1` | `16:9`, `1:1`, `9:16` | Aspect ratio savo si lavdo andro validation. |
| `stg_scale` |  | number | no | `1` | 0 – 3 | Spatio-Temporal Guidance (STG) skala, rekomendime 1.0; 0.0 zaačharel STG. |

## Example input

Required parameters only:

```json
{
  "training_data_url": "https://example.com/your-file.zip"
}
```

A fuller example:

```json
{
  "training_data_url": "https://example.com/your-file.zip"
}
```

## Run it

Set `DOITONG_API_KEY` to a key from https://doitong.com/developers/dashboard#keys. `?wait=20` returns the finished request in the same call when it is ready within 20 seconds; otherwise poll `GET /requests/{id}` (it also accepts `?wait=`), or pass `webhook_url`.

### curl

```bash
# Run the model; wait up to 20 s for the finished result in the same call
curl -X POST "https://api.doitong.com/v1/run/ltx23-trainer-v2/extend-prefix?wait=20" \
  -H "Authorization: Bearer $DOITONG_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "training_data_url": "https://example.com/your-file.zip"
  }'

# Still "queued" or "running"? Poll with the id from the response:
curl "https://api.doitong.com/v1/requests/REQUEST_ID?wait=20" \
  -H "Authorization: Bearer $DOITONG_API_KEY"
```

### JavaScript

```javascript
const API = "https://api.doitong.com/v1";
const headers = {
  "Authorization": "Bearer " + process.env.DOITONG_API_KEY,
  "Content-Type": "application/json",
};

// Run the model; wait up to 20 s for the finished result in the same call
let res = await fetch(API + "/run/ltx23-trainer-v2/extend-prefix?wait=20", {
  method: "POST",
  headers,
  body: JSON.stringify({
    "training_data_url": "https://example.com/your-file.zip"
  }),
});
let request = await res.json();
if (!res.ok) throw new Error(request.error.code + ": " + request.error.message);

// Not finished yet: long-poll until it is
while (request.status === "queued" || request.status === "running") {
  res = await fetch(API + "/requests/" + request.id + "?wait=20", { headers });
  request = await res.json();
}
if (request.status !== "succeeded") throw new Error(JSON.stringify(request.error));
console.log(request.outputs.map((o) => o.url), request.cost.credits + " API credits ($" + request.cost.usd + ")");
```

### Python

```python
import os
import requests

API = "https://api.doitong.com/v1"
headers = {"Authorization": "Bearer " + os.environ["DOITONG_API_KEY"]}

payload = {
    "training_data_url": "https://example.com/your-file.zip",
}

# Run the model; wait up to 20 s for the finished result in the same call
r = requests.post(API + "/run/ltx23-trainer-v2/extend-prefix", params={"wait": 20}, json=payload, headers=headers)
request = r.json()
if not r.ok:
    raise RuntimeError(request["error"]["code"] + ": " + request["error"]["message"])

# Not finished yet: long-poll until it is
while request["status"] in ("queued", "running"):
    request = requests.get(API + "/requests/" + request["id"], params={"wait": 20}, headers=headers).json()
if request["status"] != "succeeded":
    raise RuntimeError(request["error"])
print([o["url"] for o in request["outputs"]], request["cost"]["credits"], "API credits", "$" + request["cost"]["usd"])
```

### MCP

The MCP server at `https://api.doitong.com/v1/mcp` exposes the tools `search_models`, `get_model`, `quote`, `run`, `get_request`, `cancel_request`, `list_requests`, `create_upload` and `get_account`. A `run` call for this model:

```json
{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "tools/call",
  "params": {
    "name": "run",
    "arguments": {
      "model_id": "ltx23-trainer-v2/extend-prefix",
      "input": {
        "training_data_url": "https://example.com/your-file.zip"
      },
      "wait_seconds": 20
    }
  }
}
```

## Response

Every call returns a request object. `status` is one of `queued`, `running`, `succeeded`, `failed`, `canceled`. `outputs` lists the generated files with URLs on our storage (kept forever, or 7 days with `?storage=temporary`; `storage` says which); `output` is the model's own result object with the same URLs.

```json
{
  "id": "req_8k2m4q7x1z9c3v5b6n0p2r4t",
  "object": "request",
  "model": "ltx23-trainer-v2/extend-prefix",
  "status": "succeeded",
  "created_at": "2026-10-20T12:00:00Z",
  "started_at": "2026-10-20T12:00:02Z",
  "completed_at": "2026-10-20T12:00:09Z",
  "queue_position": null,
  "cost": {
    "credits": 12400,
    "usd": "12.40",
    "charged": 12400,
    "refunded": 0
  },
  "input": {
    "training_data_url": "https://example.com/your-file.zip"
  },
  "output": {
    "video": {
      "url": "https://content.doitong.com/dev-api/2026/10/20/req_8k2m4q7x1z9c3v5b6n0p2r4t/0-output.jpeg",
      "content_type": "image/jpeg",
      "file_name": "0-output.jpeg",
      "file_size": 1843200
    },
    "audio": {
      "url": "https://content.doitong.com/dev-api/2026/10/20/req_8k2m4q7x1z9c3v5b6n0p2r4t/0-output.jpeg",
      "content_type": "image/jpeg",
      "file_name": "0-output.jpeg",
      "file_size": 1843200
    },
    "lora_file": {
      "url": "https://content.doitong.com/dev-api/2026/10/20/req_8k2m4q7x1z9c3v5b6n0p2r4t/0-output.jpeg",
      "content_type": "image/jpeg",
      "file_name": "0-output.jpeg",
      "file_size": 1843200
    },
    "config_file": {
      "url": "https://content.doitong.com/dev-api/2026/10/20/req_8k2m4q7x1z9c3v5b6n0p2r4t/0-output.jpeg",
      "content_type": "image/jpeg",
      "file_name": "0-output.jpeg",
      "file_size": 1843200
    },
    "debug_dataset": {
      "url": "https://content.doitong.com/dev-api/2026/10/20/req_8k2m4q7x1z9c3v5b6n0p2r4t/0-output.jpeg",
      "content_type": "image/jpeg",
      "file_name": "0-output.jpeg",
      "file_size": 1843200
    }
  },
  "outputs": [
    {
      "type": "file",
      "url": "https://content.doitong.com/dev-api/2026/10/20/req_8k2m4q7x1z9c3v5b6n0p2r4t/0-output.jpeg",
      "content_type": "image/jpeg",
      "file_size": 1843200,
      "stored": true
    }
  ],
  "error": null,
  "metrics": {
    "inference_seconds": 6.8
  },
  "urls": {
    "self": "https://api.doitong.com/v1/requests/req_8k2m4q7x1z9c3v5b6n0p2r4t",
    "cancel": "https://api.doitong.com/v1/requests/req_8k2m4q7x1z9c3v5b6n0p2r4t/cancel"
  }
}
```

### Output fields (`output`)

| Field | Type | Description |
|---|---|---|
| `video` | object {url, content_type, file_name, file_size} \| null | Jekhetano video preview validationostar, kana si dostupno vašo endpoint save keren video. |
| `audio` | object {url, content_type, file_name, file_size} \| null | Jekhetano audio validationostar, preview-sar kana si dostupno kadale audio-only routes-enge: /audio-inpaint, /audio-extend-suffix, /audio-extend-prefix, /t2a, /a2a, thaj /v2a. |
| `lora_file` | object {url, content_type, file_name, file_size} | URL trained LoRA weights-enge andro .safetensors formato. |
| `config_file` | object {url, content_type, file_name, file_size} | Konfiguracija vašo inference endpoint setup. |
| `debug_dataset` | object {url, content_type, file_name, file_size} \| null | Rezultato vaš o rodipe grešken, savo si dostupno kana `debug_dataset` si putardo: jekh arhiva savi šaj huljaves thaj savi inkrel e sikavipaskere podatke pala o anglalprocesiripe. |

## Related models

- [LTX 2.3 Trainer (V2) - Audio Inpainting](https://doitong.com/developers/models/ltx23-trainer-v2/audio-inpaint.md) (`ltx23-trainer-v2/audio-inpaint`): $0.0023 / step
- [LTX 2.3 Trainer (V2) - Audio+Video Reference IC-LoRA](https://doitong.com/developers/models/ltx23-trainer-v2/ic-lora/av2av.md) (`ltx23-trainer-v2/ic-lora/av2av`): $0.0068 / step
- [LTX 2.3 Trainer (V2) - Audio+Video Reference Transformation](https://doitong.com/developers/models/ltx23-trainer-v2/av2av.md) (`ltx23-trainer-v2/av2av`): $0.0068 / step
- [LTX 2.3 Trainer (V2) - Audio-to-Audio](https://doitong.com/developers/models/ltx23-trainer-v2/a2a.md) (`ltx23-trainer-v2/a2a`): $0.0023 / step
- [LTX 2.3 Trainer (V2) - Audio-to-Audio IC-LoRA](https://doitong.com/developers/models/ltx23-trainer-v2/ic-lora/a2a.md) (`ltx23-trainer-v2/ic-lora/a2a`): $0.0023 / step
- [LTX 2.3 Trainer (V2) - Audio-to-Video](https://doitong.com/developers/models/ltx23-trainer-v2/a2v.md) (`ltx23-trainer-v2/a2v`): $0.006 / step
- [LTX 2.3 Trainer (V2) - Backward Audio Extension](https://doitong.com/developers/models/ltx23-trainer-v2/audio-extend-suffix.md) (`ltx23-trainer-v2/audio-extend-suffix`): $0.0023 / step
- [LTX 2.3 Trainer (V2) - Backward Video Extension](https://doitong.com/developers/models/ltx23-trainer-v2/extend-suffix.md) (`ltx23-trainer-v2/extend-suffix`): $0.0061 / step

## Links

- HTML page: https://doitong.com/developers/models/ltx23-trainer-v2/extend-prefix
- All models and guides for AI agents: https://doitong.com/developers/llms.txt
- OpenAPI 3.1 with this model's typed request body: https://doitong.com/developers/openapi.json?model=ltx23-trainer-v2/extend-prefix
- Errors: https://doitong.com/developers/docs/errors
- Model details as JSON: https://api.doitong.com/v1/models/ltx23-trainer-v2/extend-prefix