IAMCCS Cine FLF Length Compensator

The Cine Board Duration Lock computes a model-compatible length for a plain shot. Cine FLF Length Compensator is its sibling for the other case - the shot that carries FLF reference guides - and it accounts for something the Board Lock deliberately ignores: the guide tail. When your shot has keyframe images appended to the latent, the length you feed the model isn't just duration × fps; you need to know how many frames the guides occupy so the pipeline doesn't overrun or underrun. This node figures all of it out and reports it cleanly.

Use it whenever your shot is going through the FLF Productor / guide path rather than a bare shot. Picking this over the Board Lock is exactly the kind of choice the pack's overlapping utilities force on you - and this is the one that's correct for guided shots.

How it works

It takes your duration_seconds and frame_rate, computes raw frames, then accounts for the guide structure. The crop_guide_pixel_frames input (default 8) tells it how many pixel frames to budget for the guide tail that gets cropped after sampling. Then it rounds through the same LTX-compatible modes as the Board Lock - up_8n_plus_1 (default), nearest_8n_plus_1, or none. Because it also reads timeline_data, it can count how many guide keyframes are actually scheduled and factor that in.

Inputs and outputs

The inputs a beginner sets: duration_seconds, frame_rate, and crop_guide_pixel_frames (leave at 8 to start). timeline_data from your Shotboard makes the guide count accurate; ltx_round_mode stays on the default.

Outputs: model_length_frames (the number for your latent/length), target_frames (raw pre-rounding), guide_count (how many reference guides the timeline schedules - a nice sanity check), and report (JSON with the full math, including how many frames were reserved for the guide tail).

Installing it

Part of IAMCCS-nodes:

cd ComfyUI/custom_nodes
git clone https://github.com/IAMCCS/IAMCCS-nodes.git

Restart ComfyUI, or search "IAMCCS" in ComfyUI Manager. Baseline: ComfyUI ≥ 0.3.0, Python ≥ 3.12, Torch ≥ 2.8. No models to download.

The honest take

The one thing to internalize: Board Duration Lock and this node are not interchangeable, and the difference is the guide tail. If you run a guided shot through the Board Lock, you'll under-budget frames and your last guide can get chopped by the crop step; if you run a bare shot through this compensator, you'll reserve 8 frames you don't need. Read the report once and you'll see the budget laid out - it's the best documentation this pack has for its own frame math. And keep crop_guide_pixel_frames in sync with whatever your crop node actually removes; a mismatch between the two is a classic source of off-by-some-frames videos.