MiniMax H3 Save

Another MiniMax/internal node you'll never place by hand - but it's the one every render ends at. MiniMax H3 Save takes the assembled reel and writes the finished MP4 under output/, picture and soundtrack in one file. It's the full stop at the end of the sentence that starts at the Creator node.

It exists instead of core's CreateVideo + SaveVideo for a couple of mechanical reasons. First, SaveVideo's codec input is a dynamic combo that a Python-built graph can't assemble - and this whole pack builds its graphs in Python. Second, and more interestingly, writing the container itself is what lets a long timeline never exist as one giant concatenated tensor. The muxer streams each part of the reel off the spill disk and re-encodes it straight into the container, frame by frame. A two-minute piece is written from its parts, not from a 36 GB lump of frames sitting in RAM. Writing its own mux also means the CRF quality setting is always honored, on any ComfyUI version, instead of gated on core version support.

The inputs that matter

• reel - the whole render, all passes and any supplied clips, as the chain built it. Required.
• fps - the output framerate. Default 24, H3's native rate.
• filename_prefix - where it lands. Default minimax/H3, so you get ComfyUI/output/minimax/H3_00001_.mp4.
• crf - quality/bitrate control, default 23 (standard x264-ish sweet spot; lower is heavier, 51 is tiny).

Optional extras: takes (which card each part of the reel came from and what seed it ran on) and report (an internal assembly report the Creator UI can show). It has no outputs - it's an output node.

One subtle behavior that's actually a feature: crf is an input, not a setting read at render time. If it were a setting, changing the quality and re-queueing would be a cache hit and you'd get the same old file. Because it's an input, the save node's cache key changes and the render genuinely rewrites the file at the new quality. So if you bump the quality and nothing changes - look at whether you actually changed that input.

Notes for the curious

The workflow is embedded in the MP4's metadata unless you run ComfyUI with --disable-metadata, which means a render you drop back onto the canvas rebuilds the node that made it. The report is returned under a private mmc_video UI key with MIME metadata, so it shows up in the Jobs/Assets parser and the sidecar player.

Install is the shared pack install - ComfyUI Manager → search "H3 Creator Palette", or git clone https://github.com/z3rofeels/ComfyUI-H3-Creator-Palette into custom_nodes/, restart, hard-refresh. Requires ComfyUI 0.34.0+. And if you hand-build a graph that feeds this node a reel but forgot the audio VAE upstream in the reel chain, you'll find out at save time - the whole reel needs its sound to mux.