MiniMax H3 Extender Final Decode / Preview

You've chained six MiniMax H3 clips inside the Extender. The H3_MOTION_DISK_CACHE output that came out the other end is a manifest and a pile of latent files on disk - useful, but not something you can drag into a player. MiniMax H3 Motion Context Disk Final Decode (display name "MiniMax H3 Extender Final Decode / Preview") is the node that turns that cache into a real video file, audio and all. It's the pack's export stage, and it's an output node: nothing comes out of it, a file appears on disk instead.

What it does

It reads the cache manifest, decodes every clip's video through your vae and its audio through audio_vae, then assembles the whole sequence. The interesting part is that this isn't a dumb concat. Each adjacent pair of clips is decoded together so the seam can be corrected - the node computes a per-seam shift and applies the per-clip color corrections you made in the Extender's color editor (saturation, contrast, brightness) on top. Audio is rebuilt from decoded PCM and re-encoded once at the end, with gain matching, declicking and entry ramps, which is how you avoid an audible thunk at every cut.

In clip_by_clip mode it doubles as a live preview: after each clip renders, the cache's current sequence is assembled and written to a continuously updated file, so you see the chain growing as you validate clips, without a second VAE decode. A Save Preview button in the node saves exactly what's on screen, including seam handling and the embedded ComfyUI workflow/prompt metadata - drag that MP4 back into ComfyUI and it restores the workflow.

The inputs that matter

• cache: the H3_MOTION_DISK_CACHE output of the Extender (or the older Disk Join). Required.
• vae and audio_vae: the same ones used to generate. Missing audio_vae means silent output.
• fps: must match the FPS the cache was generated at, or the node raises an error rather than silently producing a wrong-speed file.
• codec: H.264 (default), H.265 / HEVC, or FFV1 lossless. crf (17 default) and preset (fast default) are the usual quality/speed dials.
• audio_bitrate: 128k to 320k for the AAC track.
• filename_prefix and output_directory: default to MiniMax_H3_cached in ComfyUI's output folder; leave the directory blank unless you want files elsewhere.

How to install

Same story as the whole pack - ComfyUI Manager, search MiniMax H3 Extender, or:

cd ComfyUI/custom_nodes
git clone https://github.com/tritant/ComfyUI_MiniMax_H3_Extender.git

Restart ComfyUI. The export relies on ffmpeg, and the pack's only dependency is imageio-ffmpeg, which ships a working ffmpeg binary with the install - no separate ffmpeg setup required (it falls back to a system ffmpeg if one's on PATH).

Common issues

• "Disk Final Decode fps is X, export requested Y." You changed the fps widget to something other than the cache's FPS. Match them and re-run.
• "empty cache." Nothing's been generated yet, or the cache was cleared. Generate first, decode second.
• FFV1 lossless writes a .mkv. Correct behavior, but the files are enormous - it's an archival codec, not a sharing codec. Reach for H.264 or HEVC unless you genuinely need lossless.
• VAE decode frame-count mismatch. If the VAE returns a different number of frames than the manifest expects, the node raises instead of producing a broken file - usually a sign you swapped the VAE between generation and export.

One more thing worth knowing: the ffmpeg encode runs through a bundled binary and tolerates a slow preset fine on long sequences, but a slow preset on a multi-minute video will test your patience. fast is the sweet spot for almost everyone.