# Revids

REST API for generating video from images using [LTX-2.3](https://github.com/Lightricks/LTX-2) distilled pipeline.

## Architecture

- **FastAPI** REST server with auto-generated OpenAPI docs
- **LTX-2.3 DistilledPipeline** — two-stage video generation (8 steps stage 1, 4 steps stage 2)
- **Async task queue** — submit job, poll status, download when ready
- **SQLite** — job persistence via aiosqlite
- **Single GPU lock** — jobs serialized to avoid VRAM contention

## Quick Start

```bash
# 1. Clone the repo (including LTX-2 submodule)
git clone --recursive <repo-url> revids
cd revids

# 2. Create venv and install LTX packages (editable, from submodule)
python -m venv .venv && source .venv/bin/activate
pip install -e libs/LTX-2/packages/ltx-core -e libs/LTX-2/packages/ltx-pipelines

# 3. Install API dependencies
pip install -r requirements.txt

# 4. Download model weights from HuggingFace
## Distilled model checkpoint
huggingface-cli download Lightricks/LTX-2.3 \
  --include "ltx-2.3-22b-distilled-1.1.safetensors" \
  --local-dir models/

## Spatial upsampler (required for two-stage pipeline)
huggingface-cli download Lightricks/LTX-2.3 \
  --include "ltx-2.3-spatial-upscaler-x2-1.1.safetensors" \
  --local-dir models/

## Gemma text encoder
huggingface-cli download google/gemma-3-12b-it-qat-q4_0-unquantized \
  --local-dir models/gemma-3-12b-it-qat-q4_0-unquantized

# 5. Optimize memory (optional but recommended)
export PYTORCH_CUDA_ALLOC_CONF=expandable_segments:True

# 6. Run
uvicorn app.main:app --reload
```

The API is available at `http://localhost:8000`. Swagger docs at `http://localhost:8000/docs`.

## API Endpoints

### Submit Job — `POST /generate`

Upload an image and generation parameters. Returns a job ID immediately.

```bash
curl -X POST http://localhost:8000/generate \
  -F "image=@photo.jpg" \
  -F "prompt=A cinematic pan right across a misty mountain range at dawn, golden light breaking through clouds" \
  -F "width=768" \
  -F "height=512" \
  -F "num_frames=97" \
  -F "fps=24.0" \
  -F "seed=42"
```

**Parameters:**

| Param | Type | Default | Description |
|---|---|---|---|
| `image` | file (required) | — | Input image (PNG, JPG, WebP, etc.) |
| `prompt` | string | `""` | Optional text prompt to guide generation |
| `width` | int | 768 | Output width (must be divisible by 32) |
| `height` | int | 512 | Output height (must be divisible by 32) |
| `num_frames` | int | 65 | Frame count (must be `8n+1`: 9, 17, …, 65, 97, 121, 161, 257) |
| `fps` | float | 24.0 | Frames per second |
| `seed` | int | random | Random seed for reproducibility |

**Response:**
```json
{
  "job_id": "abc123def456",
  "status": "pending",
  "message": "Job submitted. Poll GET /jobs/{job_id} for status."
}
```

### Check Job Status — `GET /jobs/{job_id}`

```bash
curl http://localhost:8000/jobs/abc123def456
```

**Response:**
```json
{
  "job_id": "abc123def456",
  "status": "completed",
  "prompt": "A cinematic pan right...",
  "params": {"width": 768, "height": 512, "num_frames": 97, "fps": 24.0, "seed": 42},
  "error": null,
  "created_at": "2025-01-01T12:00:00+00:00",
  "completed_at": "2025-01-01T12:01:30+00:00"
}
```

**Status values:** `pending` → `processing` → `completed` or `failed`

### Download Video — `GET /jobs/{job_id}/download`

Returns the `.mp4` video file when the job is completed. Returns 404 if not ready.

```bash
curl http://localhost:8000/jobs/abc123def456/download -o output.mp4
```

### Delete Job — `DELETE /jobs/{job_id}`

Removes the job record and associated video file.

```bash
curl -X DELETE http://localhost:8000/jobs/abc123def456
```

### Health Check — `GET /health`

Returns GPU availability and device info.

```bash
curl http://localhost:8000/health
```

```json
{"status": "ok", "gpu": true, "gpu_name": "NVIDIA A100-SXM4-80GB"}
```

## Frame Count Reference

Num_frames must follow `8n+1` pattern. Common values:

| Frames | Duration (24 fps) | Duration (25 fps) |
|---|---|---|
| 65 | ~2.7s | ~2.6s |
| 97 | ~4.0s | ~3.9s |
| 121 | ~5.0s | ~4.8s |
| 161 | ~6.7s | ~6.4s |
| 257 | ~10.7s | ~10.3s |

## Resolution Reference

Width and height must be divisible by 32 (min 256, max 2048).

| Resolution | Aspect Ratio |
|---|---|
| 768×512 | 3:2 landscape |
| 512×768 | 2:3 portrait |
| 704×512 | 4:3 standard |
| 640×640 | 1:1 square |

## Configuration

All settings can be overridden via `.env` file (placed in project root) or environment variables prefixed with `REVIDS_`. See `app/config.py` for all available options.

| Env Variable | Default | Description |
|---|---|---|
| `REVIDS_LTX_DISTILLED_CHECKPOINT` | `models/ltx-2.3-22b-distilled-1.1.safetensors` | Distilled model checkpoint path |
| `REVIDS_LTX_GEMMA_ROOT` | `models/gemma-3-12b-it-qat-q4_0-unquantized` | Gemma text encoder path |
| `REVIDS_LTX_SPATIAL_UPSAMPLER` | `models/ltx-2.3-spatial-upscaler-x2-1.1.safetensors` | Spatial upsampler checkpoint |
| `REVIDS_LTX_QUANTIZATION` | `fp8_cast` | Quantization: `fp8_cast`, `fp8_scaled_mm`, or `""` (bfloat16) |
| `REVIDS_LTX_LORAS` | *(empty)* | LoRA config: `"path1:1.0,path2:0.5"` |
| `REVIDS_MAX_CONCURRENT_JOBS` | `1` | Concurrent GPU jobs |
| `REVIDS_PORT` | `8000` | Server port |
| `REVIDS_RELOAD` | `true` | uvicorn auto-reload |

### LoRA Support

To load custom or Lightricks LoRAs:

```bash
# Single LoRA at full strength
export REVIDS_LTX_LORAS="models/my-style.safetensors:1.0"

# Multiple LoRAs
export REVIDS_LTX_LORAS="models/style.safetensors:1.0,models/motion.safetensors:0.5"
```

Lightricks-published LoRAs:
- [IC-LoRA Union Control](https://huggingface.co/Lightricks/LTX-2.3-22b-IC-LoRA-Union-Control)
- [IC-LoRA Motion Track Control](https://huggingface.co/Lightricks/LTX-2.3-22b-IC-LoRA-Motion-Track-Control)
- [IC-LoRA LipDub](https://huggingface.co/Lightricks/LTX-2.3-22b-IC-LoRA-LipDub)
- Camera Control LoRAs (dolly in/out, jib up/down, static, etc.)

## Memory Optimization

```bash
# Improve CUDA memory allocation fragmentation
export PYTORCH_CUDA_ALLOC_CONF=expandable_segments:True

# Use FP8 quantization (~40% VRAM reduction, minimal quality loss)
export REVIDS_LTX_QUANTIZATION=fp8_cast

# For Hopper GPUs (H100) with TensorRT-LLM:
# export REVIDS_LTX_QUANTIZATION=fp8_scaled_mm
```

## Hardware Requirements

- **GPU**: NVIDIA with CUDA support
- **VRAM**: ≥ 24 GB (bfloat16), ~14 GB with FP8 quantization
- **Disk**: ~30 GB for all model weights (distilled + upsampler + Gemma encoder)

## Project Structure

```
revids/
  app/
    __init__.py
    main.py            # FastAPI app + HTTP routes
    config.py          # Settings (pydantic-settings, env var support)
    models.py          # Request/response Pydantic models
    service.py         # LTX pipeline wrapper, job processing, video encoding
    database.py        # SQLite job store (aiosqlite)
  libs/
    LTX-2/             # LTX-2 git submodule (source for ltx-core/ltx-pipelines)
  videos/              # Generated .mp4 output (gitignored)
  requirements.txt
  .gitignore
```

## Prompting Guide

For best results with LTX-2.3, write detailed, chronological motion descriptions:

1. Start with the main action in one sentence
2. Add specific movement details and gestures
3. Describe appearances precisely
4. Include background and environment
5. Specify camera angle and movement
6. Describe lighting and color palette
7. Keep under 200 words

Full guide: [https://ltx.video/blog/how-to-prompt-for-ltx-2](https://ltx.video/blog/how-to-prompt-for-ltx-2)

## License

See [LTX-2 LICENSE](libs/LTX-2/LICENSE) for model usage terms.