Matte Monitor

Matte Monitor is the smallest node in ComfyTV's keying suite, and skipping it is how you end up with a composite you can't explain. The whole discipline of pulling a clean key is inspecting the matte - the black-and-white alpha - before you ever put the subject over a background. This stage does exactly that: it takes your keyed video and outputs the alpha as a video you can actually look at, with a single control for how it's displayed.

ComfyTV is the canvas-style app layer on ComfyUI where every operation is its own node. In the keying chain (Keyer → Matte Morphology → Key Mix) Matte Monitor is the QC checkpoint you slot in after the Keyer: pull the key, monitor the matte, fix it, then composite.

How it works. It renders the alpha channel of the input as a grayscale video: pure white where the subject is fully opaque, pure black where it's fully transparent, and all the messy grays in between - which is exactly where your problems live. A soft, noisy or holey matte is obvious the moment you see it in black and white, and invisible when you're staring at the full-color composite. The single slope control (0–1, default 0.5) adjusts the display's contrast ramp on the matte, which is a view aid - it doesn't change the underlying key, just how the grays read on screen, useful for spotting near-transparent regions that are eating the subject's edge.

The inputs that matter. The force_run_token, project_id and parent_output_id inputs are internal plumbing. The real ones:

• video - the keyed footage to monitor (required; the node errors without it).
• slope - display contrast on the matte, 0–1.

Output is a video - the matte itself, which you can also reuse as a mask input further down the chain.

Install. Install the pack once:

cd ComfyUI/custom_nodes
git clone https://github.com/jtydhr88/ComfyTV

Restart ComfyUI (full restart, not a browser refresh) and the stage appears under ComfyTV → Keying. ComfyUI Manager - search "ComfyTV" - works too. Zero Python dependencies (the pack's pyproject.toml dependency list is empty) and no model files - it's a display transform on your GPU. Desktop/multi-install users: clone into the running instance's path from the startup log or the node won't register.

Where people get burned. The most common "failure" is really a workflow miss: someone wires the Keyer straight into Key Mix, skips monitoring, and then fights a fringe they can't diagnose - because it was visible in the matte all along. Run it after the Keyer and before cleaning up; the gray edge noise you see there is the thing Matte Morphology fixes. Second: slope is a display aid, not a keying parameter - don't expect it to change the actual composite. And one genuine gotcha: the node outputs the matte, so if you're using it as the final "view", you're watching alpha, not the composite - switch the Keyer's output to composite (or add Key Mix) when you want the finished picture.