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hao-ai-lab-FastVideo/docs/inference/configuration.md
2026-10-07 04:46:26 -07:00

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# Configuration
## Multi-GPU Setup
FastVideo automatically distributes the generation process when multiple GPUs are specified:
```python
# Will use 4 GPUs in parallel for faster generation
generator = VideoGenerator.from_pretrained(
"Wan-AI/Wan2.1-T2V-1.3B-Diffusers",
num_gpus=4,
)
```
One node uses the multiprocessing executor (`execution_backend: mp`, the
default). With `num_gpus=1`, `mp` automatically selects the in-process (`uni`)
executor so weights load in the current process. Set `execution_backend: uni`
to force that path. Two machines — for example two DGX Sparks, one GPU each —
need Ray:
```yaml
generator:
engine:
num_gpus: 2
execution_backend: ray
parallelism:
sp_size: 2
```
Set `RAY_ADDRESS` and `FASTVIDEO_HOST_IP` to the interconnect IPs, not Wi-Fi.
The FastH3 example selects Ray automatically when `RAY_ADDRESS` is set. Full
bring-up: [Pair two NVIDIA DGX Sparks](../getting_started/installation/spark_pair.md).
## Customizing Generation
- `PipelineConfig`: Initialization time parameters
- `SamplingParam`: Generation time parameters
You can customize generation behavior using `PipelineConfig` and
`SamplingParam`:
```python
from fastvideo import VideoGenerator, SamplingParam, PipelineConfig
def main():
model_name = "Wan-AI/Wan2.1-T2V-1.3B-Diffusers"
config = PipelineConfig.from_pretrained(model_name)
config.vae_precision = "fp16"
# Create the generator
generator = VideoGenerator.from_pretrained(
model_name,
num_gpus=1,
dit_layerwise_offload=True, # FastVideoArgs option
pipeline_config=config
)
# Create and customize sampling parameters
sampling_param = SamplingParam.from_pretrained("Wan-AI/Wan2.1-T2V-1.3B-Diffusers")
# How many frames to generate
sampling_param.num_frames = 45
# Video resolution (width, height)
sampling_param.width = 1024
sampling_param.height = 576
# How many steps we denoise the video (higher = better quality, slower generation)
sampling_param.num_inference_steps = 30
# How strongly the video conforms to the prompt (higher = more faithful to prompt)
sampling_param.guidance_scale = 7.5
# Random seed for reproducibility
sampling_param.seed = 42 # Optional, leave unset for random results
# Generate video with custom parameters
prompt = "A beautiful sunset over a calm ocean, with gentle waves."
video = generator.generate_video(
prompt,
sampling_param=sampling_param,
output_path="my_videos/", # Controls where videos are saved
save_video=True
)
# If return_frames=True, frames are available in video["frames"]
print(f"Generated {len(video['frames'])} frames")
if __name__ == '__main__':
main()
```
## JSON/YAML Config Files (CLI)
The inference CLI is config-first. Use an explicit subcommand with `--config`,
then apply optional dotted overrides on top, matching the training CLI style.
By default, CLI generation uses `return_frames=false` unless you set
`request.output.return_frames: true` in config or via a dotted override.
```bash
fastvideo generate --config config.yaml
```
Example nested config:
```yaml
generator:
model_path: FastVideo/FastHunyuan-diffusers
engine:
num_gpus: 2
parallelism:
sp_size: 2
request:
prompt: A capybara relaxing in a hammock
sampling:
num_frames: 45
height: 720
width: 1280
num_inference_steps: 6
seed: 1024
output:
output_path: outputs/
```
`generator.engine.execution_backend` accepts `mp`, `uni`, `ray`, or
`external_launcher`. The last option is for synchronized offline generation
under `torchrun` or `srun`; it is not supported by `fastvideo serve`. Set
`generator.engine.num_gpus` and the relevant parallelism sizes to the total
launcher world size. See the [distributed inference contract](architecture.md#distributed-inference)
and the [MiniMax-H3 run config](https://github.com/hao-ai-lab/FastVideo/blob/main/examples/inference/basic/minimax_h3_external_launcher.yaml).
`generator.engine.parallelism.dist_timeout` is an optional positive integer
in **seconds**. FastVideo applies it to the default process group when
FastVideo initializes that group, and to every FastVideo-created device and
Gloo control group. If it is omitted, PyTorch's backend defaults apply. This
timeout bounds a missing collective participant; external launchers should
still supervise the full worker group and terminate peers when one rank exits.
Override individual values from the CLI with dotted paths:
```bash
fastvideo generate --config config.yaml --request.sampling.seed 42
```
## Performance Optimization
For configuring optimizations, please see our [optimizations guide](optimizations.md)