BIM-VFI Segment Interpolate

Here's the thing nobody tells you about long video interpolation: VRAM gets all the attention, but for a 10-minute clip it's RAM that dies first. The plain BIM-VFI Interpolate node bounds VRAM via chunk_size, but the full interpolated output still has to live in memory somewhere. BIM-VFI Segment Interpolate is the version that admits it - it only produces one segment's worth of output frames at a time, so peak RAM stays proportional to your segment size instead of your whole video.

It's the same BIM-VFI interpolation under the hood: same model, same multiplier (2x/4x/8x, recursive passes), same batch_size, chunk_size, keep_device, all_on_gpu, clear_cache_after_n_frames, and the same source_fps/target_fps exact-FPS selection. The two new inputs are the point:

• segment_index (0-based) - which slice of the input this node processes.
• segment_size (default 500) - input frames per segment. Adjacent segments overlap by one frame so stitching is seamless.

How the pattern works. You lay down one Segment Interpolate per segment, each with segment_index = 0, 1, 2…, and chain them by wiring the previous node's model output into the next one's model input. That model pass-through is the trick: it forces sequential execution, so segment 0 finishes, you save its frames to disk with a Video Combine node, that save frees the RAM, and only then does segment 1 run. Peak RAM is bounded by one segment instead of the whole movie. It's fiddly - ComfyUI doesn't do loops here, so it's a chain of nodes, not a single config - but it's the difference between "this runs" and "my machine eats its own desktop."

When you're done, point Tween Concat Videos at the saved segment files to glue them back into one video, and keep the loader's frame rate, the node's source_fps/target_fps, and Video Combine's frame_rate synchronized or you'll get a stutter you can't explain.

Install. Search "Tween" in ComfyUI Manager, or:

cd ComfyUI/custom_nodes
git clone https://github.com/Ethanfel/ComfyUI-Tween
pip install -r requirements.txt

Restart, then let the Load BIM-VFI Model node auto-download the checkpoint on first use. You'll also want VideoHelperSuite for the Load Video and Video Combine nodes that feed and drain this chain.

Common issues. If a segment reports no target timestamps when you're downsampling, your segment_size is too small to span one output-frame interval - bump it up. If you chain segments but skip saving between them, you've defeated the whole purpose; the RAM never gets freed. And remember the model pass-through chain is mandatory - two Segment nodes wired to the same source will run in parallel and blow your RAM budget anyway.