FastH3 8-Step V2 ComfyUI Workflow | INT8 Video + Audio

FastH3 V2 makes smooth videos with audio in just eight steps.

Who it's for: creators who want this pipeline in ComfyUI without assembling nodes from scratch. Not for: one-click results with zero tuning - you still choose inputs, prompts, and settings.

Open preloaded workflow on RunComfy

Open preloaded workflow on RunComfy (browser)

Why RunComfy first
- Fewer missing-node surprises - run the graph in a managed environment before you mirror it locally.
- Quick GPU tryout - useful if your local VRAM or install time is the bottleneck.
- Matches the published JSON - the zip follows the same runnable workflow you can open on RunComfy.

When downloading for local ComfyUI makes sense - you want full control over models on disk, batch scripting, or offline runs.

How to use (local ComfyUI)
1. Load inputs (images/video/audio) in the marked loader nodes.
2. Set prompts, resolution, and seeds; start with a short test run.
3. Export from the Save / Write nodes shown in the graph.

Expectations - First run may pull large weights; cloud runs may require a free RunComfy account.

Overview

You choose the first and last frames. FastH3 V2 creates a continuous MiniMax H3 video between them. You get generated audio and smooth motion. Eight-step INT8 inference saves time. Sparse attention boosts efficiency. Make cinematic transitions and short stories with defined start and end shots.

Important nodes:

Key nodes in ComfyUI FastH3 8-Step V2 ComfyUI Workflow

MiniMaxH3ImageToVideo (#155)
- Builds the conditioning from your first and last reference frames plus the prompt, and outputs an initial latent for joint video-and-audio generation. Tune the text prompt to describe motion, camera, atmosphere, and any desired sound cues. Keep identities and scene elements consistent with the references for the most stable results. Adjust the duration control in the left group to change clip length without touching sampler settings.

BlockSparseAttention (#158)
- Applies sparse attention to the loaded model to accelerate sampling while preserving attention where it matters most. If you see detail loss in busy scenes, increase the kept fraction or reserve additional tokens for foreground subjects. For simple scenes, stronger sparsity can significantly speed up renders.

MiniMaxH3SigmaShift (#160)
- Shifts the noise schedule for video and audio so temporal structure and sound remain coherent across the short eight-step trajectory. If motion looks jittery, nudge the video shift higher; if audio alignment drifts, adjust the audio shift slightly. Use small changes and test short previews to find a balance.

SamplerCustomAdvanced (#149)
- Runs the eight-step denoising with the res_multistep sampler and the schedule from BasicScheduler (#148). Keep the seed fixed in RandomNoise (#153) for reproducibility, then vary it to explore alternates once you like the motion. Strong guidance from the BasicGuider (#150) helps adhere to the prompt when compositions are complex.

CreateVideo (#154)
- Muxes decoded frames and audio into a final clip. Set frames per second to control cadence, choose a color space for your workflow, and if you plan to edit later, pick a codec that balances size and quality for your NLE.

Notes

FastH3 8-Step V2 ComfyUI Workflow | INT8 Video + Audio - see RunComfy page for the latest node requirements.