MiniMax H3 Contex Loop Export PNG Sequence

MiniMax H3 Contex Loop Export PNG Sequence is the "I need actual frames, not a compressed MP4" node. Assembly gives you a single H.264 file; this gives you a continuous, lossless PNG sequence of every delivered frame across every accepted scene - trimmed of the repeated context overlap, numbered continuously, and written to disk without ever holding the whole production in memory.

Why would you want that? Because H.264 is lossy, and if your next step is an external tool - an interpolator, an editor, a photogrammetry pass, a VAE decode you want bit-exact - you want the cleanest possible source. Also, a long chain at 2K is genuinely too big to hold as one IMAGE tensor; this node exists precisely so the export doesn't blow up your RAM.

How it works

Unlike Assemble, which stream-copies the saved H.264 segments, this node re-decodes each checkpoint latent with the VAE you used for the original render. The tooltip on video_vae is worth quoting: decode precision and VAE settings determine whether regenerated pixels exactly match the first decode. So the PNGs come from the latent, not the compressed preview - that's the point.

Inputs: manifest (completed or partial, from Loop End or Manifest Load - the H.264 segments are not used), video_vae (the same VAE as the original render), export_name (folder name under output/h3_chains/<run>/frames; an existing folder is never overwritten, you get a numbered sibling), first_frame_number (default 1; frames continue across scene boundaries without resetting), png_compression (0–9, default 4; 0 is fastest and largest, 9 is slowest and smallest - it does not change pixels), and embed_workflow (default true: embeds the archived workflow, API graph, effective plan and chain manifest in the first PNG, plus per-scene prompt metadata in each scene's first frame).

Outputs: output_directory (the folder with the sequence plus export.json), frame_count, and status.

The honest read

The embed_workflow default is a small act of genius for provenance - your exported frames literally carry the Plan that made them, which is exactly what you want if you're sending a sequence to a client or revisiting it months later. On the flip side, if you just need quick preview frames, this is overkill; Assemble's MP4 is faster to generate and fine for review. Reach for PNG export when fidelity or external tooling matters.

Installing it

Part of ComfyUI-MiniMaxH3-Contex-Loop (ComfyUI Manager: "MiniMax H3 Contex Loop"), or:

cd ComfyUI/custom_nodes && git clone https://github.com/ethanfel/ComfyUI-MiniMaxH3-Contex-Loop.git

Restart ComfyUI. Standing requirements: H3 weights, current ComfyUI with native Add Guide (PR #15439). No ffmpeg needed here - this is pure VAE decode plus PNG write.

Common issues

The big one is the VAE mismatch: use a different video_vae than the render and your "regenerated" pixels differ from the first decode - subtle color drift you'll chase for hours. Keep the exact same VAE. And a partial manifest exports only what's contiguous and saved; check status for the scene count before you assume you got everything.