Image Batch Slice (C2C)

Image Batch Slice (C2C) is the node equivalent of Python's video[start:end:step] - and if you've ever needed to process only frames 10 through 60 of a video batch, or every second frame of a 100-frame sequence, you know the fiddly alternative: a ChainNode, a bunch of math, or loading the video three times. This just does the slice, cleanly, with Python's slice semantics you already half-know.

It's part of the C2C Helpers in ComfyUI-CustomNodePacks, the ~72-node pack from Code2Collapse (Likhith-24, active on r/comfyui). A pack this size needs a "utility drawer," and this is the frame-range drawer.

How it works

You feed it an images batch (a [B,H,W,C] tensor - a video loaded into ComfyUI is just a batch of frames) and three ints:

• start - first frame, inclusive. Negative counts from the end of the batch.
• end - exclusive, Python-style: the slice stops before this frame. -1 means "to the end of the batch", which is the default.
• step - stride. 1 keeps every frame; 2 keeps every second frame (frame decimation for faster testing); 4 keeps every fourth.

Negative values work like Python: start=-30 starts 30 frames from the end, and the node clamps everything into the valid range rather than erroring on out-of-bounds values. Outputs are the sliced images plus frame_count (INT), which is convenient for wiring into downstream logic like save filename prefixes.

It's the same idea as the pack's Frame Range Router (MEC), minus the mask routing - this one is a bare-bones batch-only slice.

The inputs and outputs that matter

• images - the only required input.
• start / end / step - the three ints above. The two you'll actually touch: start and end. Leave step at 1 unless you're deliberately decimating.
• images out - the sliced batch.
• frame_count (INT) - how many frames you got; wire it into a filename or a counter.

Installing it

Ships inside ComfyUI-CustomNodePacks, no separate repo. ComfyUI Manager → search "CustomNodePacks", or:

cd ComfyUI/custom_nodes
git clone https://github.com/Code2Collapse/ComfyUI-CustomNodePacks.git

Pure PyTorch, no extra dependencies, no models, no VRAM. The pack overall wants opencv-python>=4.7.0 and scipy>=1.10.0 for other nodes - add just those if missing (skip the full requirements.txt, which can overwrite ComfyUI's torch). Restart ComfyUI.

Common issues

• Got fewer frames than expected - check whether you meant end inclusive. It's exclusive. Want frames 0-9? That's start=0, end=10.
• Empty result - start at or past end, or a step that skips everything. The node clamps instead of erroring, so check frame_count on the output.
• You only want to view a range, not reshape the batch - this node genuinely slices; the pack's Video Frame Player (MEC) is the in-graph scrubber if your goal is preview instead of processing.

The honest take: it's a one-liner you could write in a custom script node - but you won't, because this exists, is already installed with the pack, and reads exactly like the Python you already know.