h3.c: Native MiniMax-H3 Inference on Apple Silicon by antirez

ComfyUI Wikinews

antirez, creator of Redis, builds h3.c, a native Metal-based MiniMax-H3 inference engine for Apple Silicon with prompt-to-video/audio and Ref2VA references working end to end.

antirez (Salvatore Sanfilippo, the developer behind Redis and Lua) is building h3.c, a native MiniMax-H3 inference engine for Apple Silicon. The core pipeline already works end to end on Macs: prompt-to-video/audio, first/last-frame conditioning, and ordered Ref2VA image/video/audio references all function, with current work focused on H3-specific Metal performance and memory optimization on M3 Max and M5 Max.

H3 on Mac Hardware

Running MiniMax-H3 in ComfyUI requires a high-VRAM CUDA or AMD GPU. h3.c takes a different route: a single C codebase (with Objective-C and Metal shaders) that runs H3 directly on Apple's GPU via Metal, letting M-series Macs generate H3 video and audio locally without a discrete GPU or a cloud instance. The project reached over 1,100 GitHub stars within days of going public.

What Works Today

  • Prompt-to-video and prompt-to-audio generation from the official MiniMax-H3 weights
  • First/last-frame conditioning via the interactive session (!first, !last)
  • Ordered Ref2VA references — multiple reference images appended in order and exposed to the model as <Picture 1>, <Picture 2>, etc.
  • Interactive Iris-style CLI that keeps prompt conditioning, prepared DiT, and the video decoder in memory between generations
  • Native 256 preview generation and an original-BF16 SSD-streamed DiT mode for memory-constrained machines

Getting Started

The README walks through building and running the engine. With the Hugging Face snapshot of MiniMax-H3 in ./MiniMax-H3:

make -j8
mkdir -p outputs
./h3 --info -d ./MiniMax-H3
./h3 -d ./MiniMax-H3 --width 512 --height 512 --steps 6

Without -p, the binary starts an interactive session where you type a prompt to generate a numbered video. Useful session commands include !status, !seed random, !seconds 2, !show, !save output.mp4, !first, !last, !ref-image, and !cache.

Status

The project is under active development, with commits landing daily. The README notes that the current work is incremental H3-specific Metal performance and memory optimization, so expect both speedups and rough edges on M-series hardware.

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h3.c: Native MiniMax-H3 Inference on Apple Silicon by antirez | ComfyUI Wiki