HR Endless Sampler: Any-Length MiniMax H3 Videos on 16GB VRAM
HR Endless Sampler is a ComfyUI custom node that renders unlimited-length MiniMax H3 videos by splitting inference into chunks, using Gemma to keep continuity.
HR Endless Sampler is a new ComfyUI custom node by u/rhradec that renders MiniMax H3 videos of any length by automatically splitting inference into small chunks, making long video generation possible on a single 16GB GPU. The same approach also renders 1080p videos of arbitrary length within that VRAM budget (GitHub | Reddit thread).
625 frames of 1080p MiniMax H3 video rendered on a single 16GB GPU with chunked sampling
Official demo: 1080p, 625-frame MiniMax H3 video generated on one 16GB GPU
How it works
The node is a drop-in chunked replacement for ComfyUI's SamplerCustomAdvanced, currently supporting MiniMax H3 (LTX 2.5 support is planned next). Instead of sampling one long latent in a single pass, it:
- Splits the inference into small chunks of the same long latent, sized to fit your VRAM.
- Plans the production with Gemma4 12B QAT: the built-in LLM analyzes your original prompt and all reference images, then plans action timing for each shot and each chunk.
- Rewrites per-chunk prompts: after each chunk it analyzes the previously rendered frames and writes new small prompts that maintain continuity and coherence across the whole video.
- Carries continuation frames: a configurable number of completed frames from the previous chunk (22 by default) seed the next chunk so transitions stay seamless.
Smaller chunks use less VRAM but need more handoffs. For example, 39 frames is a practical 1080p starting point on a 16GB GPU; with 73-frame chunks you can render 1080p on 16GB before accounting for reference frames.
Built-in preview and video players
The extension installs four nodes:
| Node | Purpose |
|---|---|
HR Endless Sampler | Samples the long latent serially, asks Gemma to plan the full production and direct each chunk, and outputs the finished latent, chunk prompts, and timeline metadata. |
HR Endless Sampler Preview | Live accumulated preview with ordered chunk playback, shot brackets, prompt/timing tooltips, frame stepping, and performance graphs. |
HR Endless Sampler Save Video | Saves standard video, animated VHS formats, or float EXR sequences while preserving the Endless timeline, prompts, and chunk mapping. |
HR Endless Sampler Load Video | Browses finished media and restores its interactive timeline in the browser, outputting video, audio, and timeline metadata. |
The preview and save/load nodes share a colored chunk timeline with shot brackets:
 |  |
|---|---|
| Live preview during inference | Chunk timeline with per-chunk prompts and timing |
Hovering a chunk shows the exact H3 prompt Gemma created for it plus a timing breakdown of sampler, Gemma, and misc work, and a "Matching Videos" button lets you compare previous renders of the same filename prefix side by side.
Availability
HR Endless Sampler is open source under Apache-2.0. Install it by cloning the repository into ComfyUI/custom_nodes/ and restarting ComfyUI. The README documents all settings including chunk_frames and video_continuation, and the author is active in the Reddit thread helping users tune it for 12GB cards. A more aggressively quantized Gemma variant and an OpenAI-endpoint option (to run the re-prompting LLM in the cloud with zero local VRAM) are planned.
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