PulpCut/FastH3-VSA-INT8-ConvRot

FastH3 VSA · H3ddle INT8 ConvRot

This repository contains the learned-VSA FastH3 Preview v1 transformer converted for H3ddle's native Apple-Silicon Metal engine. It is published with permission from the MiniMax/Hailuo team and remains subject to the included MiniMax H3 Community License Agreement.

Use in H3ddle

FastH3 · VSA is included in H3ddle's managed model catalog. Users do not need to download this repository manually, merge checkpoints, run a conversion script, or configure a model folder. In H3ddle, open Models, choose FastH3 · VSA under Video, and select Install. The app downloads and verifies this pinned transformer and reuses shared H3 components that are already installed.

The source checkpoint is FastVideo/FastVideo-FastH3-4-step-Preview-v1-VSA-DataFree at revision b65818d41939b5085451074fe8ca8b799f8d4921.

Package

diffusion_models/minimax_h3_fl2va_pruned_int8_convrot.safetensors

• Size: 22,966,486,018 bytes
• SHA-256: 53335dfb80a09e9de0ef8dce2ef36b5b91e9167044b4da7a3a1219746f474f40
• H3ddle profile: fasth3
• Serving schedule: exactly four calls
• Attention: learned VSA, format 2, tile size 64, sparsity 0.9
• Conditioning: text-to-video with jointly generated audio only

The conversion keeps H3ddle's input-major INT8 ConvRot transformer core, translates Diffusers' value-first SwiGLU layout to the native engine's gate-first layout, preserves the trained four-call AdaLN function as exact lookup rows, and includes all 50 learned VSA compression-gate projections.

This file is not a Diffusers checkpoint. Use it with H3ddle/h3.c and the shared MiniMax H3 text encoder, video VAE, audio VAE, tokenizer, and configuration files expected by the app's managed model manifest.

Apple Silicon performance

A controlled 512×512, 124-frame comparison on a 32 GB M1 Pro used the same prompt, soundscape, seed, and cache settings. The measured outputs were 5.175-second H.264 clips at 24 fps with stereo AAC:

H3 model	Released passes	Attention	End-to-end time	Compared with VSA	Evidence
Standard	20	Dense	4,253 s (70.9 min)	~6.11× slower	Schedule-normalized estimate
Turbo	8	Dense	1,782 s (29.7 min)	~2.56× slower	Schedule-normalized estimate
FastH3 Dense	4	Dense	958.174 s (16.0 min)	1.377× slower	Measured conversion baseline
FastH3 · VSA	4	Learned VSA, 90% sparse	696.043 s (11.6 min)	Baseline	Measured

The Standard and Turbo rows are estimates, not completed matched runs. They subtract the 134.439-second fixed pipeline cost observed in a phase-instrumented matched-shape receipt, scale only the measured dense transformer work from four passes to the released 8- and 20-pass schedules, and then add the fixed cost back. The FastH3 Dense and VSA rows are direct end-to-end measurements.

These are local M1 Pro results, not projections for every Apple-Silicon device. The direct four-call comparison is a 27.4% end-to-end reduction, or 1.377× throughput, for learned VSA versus Dense.

The native deterministic VSA GPU/CPU test measured cosine similarity 0.999998633, mean absolute error 0.000065549, and maximum error 0.000706643 after BF16 output rounding.

Limitations

FastH3 Preview v1 supports 124–362 frames and requires a short edge of at least 480 pixels. It does not support still-image generation, start/end frames, ordered image references, or video inpainting. H3ddle enforces these constraints in both the app and the native engine.