h3.c

H3.c generates video with synchronized audio locally on a Mac. It's a from-scratch C inference engine for MiniMax's H3 model, written by the creator of Redis, with an interactive REPL that previews output right in your terminal. The code is MIT and a pleasure to read; local, private video generation with no cloud API is the pitch.

The hardware is the gate. You want Apple Silicon with serious unified memory: peak usage runs into the tens of gigabytes depending on canvas size, plus about 37 GB of disk for the checkpoint. An SSD-streaming mode drops memory use to around 2 GB, but at a steep speed penalty at small canvas sizes. Build is a simple make with FFmpeg on PATH.

This is for Mac owners with serious unified memory who want local generation, and for anyone who wants to read a modern diffusion pipeline in C. ComfyUI is the mainstream local workbench; Runway and Pika are the hosted alternatives.

The catch: the MIT badge covers only the code. The model weights ship under MiniMax's custom community license, non-OSI, with an application process for US, EU, UK, and South Korea users, and the engine is useless without them. The author also frames the repo as working vertical slices, not a finished product, and canvas sizes and frame counts have sharp constraints.