FL Audio Beat Visualizer

This is the simplest node in Fill-Nodes' audio-reactive family - it turns a beat sequence into a strobing frame sequence, either flat black/white flashes or cycling through a batch of images you supply. It's the "does my beat data actually line up" sanity check before you build anything fancier with the pack's more elaborate reactive nodes, and it also works as a literal strobe layer in its own right for VJ-style content.

How it works

You feed it sequence_json - beat/shot timing data produced upstream by this pack's BPM analysis and sequencing nodes (this node reads that structure but doesn't generate it itself). At each detected beat change, it flips the visual state: if use_black_white is on (the default), it just alternates full black and full white frames; if you supply an images batch and turn use_black_white off, it cycles through those images on each beat instead. start_with_white decides which state the first frame opens on, which matters if you're trying to align the strobe's phase with a specific downbeat rather than an arbitrary starting point.

The inputs and outputs that matter

Required: sequence_json - the only required field, and the one thing you can't skip; without valid sequence data there's nothing to visualize.

Optional: images (a batch to cycle through instead of black/white), use_black_white (default true - the switch between the two modes described above), width/height (default 512, up to 4096), start_with_white (default false).

Output: frames - a batch of IMAGE frames, ready to preview, save, or composite as a strobe layer over other footage.

How to install it

ComfyUI Manager: search ComfyUI_Fill-Nodes, install, restart. Or:

cd ComfyUI/custom_nodes
git clone https://github.com/filliptm/ComfyUI_Fill-Nodes

then restart. This specific node has no heavy dependency of its own - the audio analysis work happens upstream, in whichever node produced your sequence_json.

Common issues & troubleshooting

You fed images but it still flashes black/white. Check use_black_white - the node has two mutually exclusive modes gated by a single boolean, and it defaults to the black/white mode. Turn it off for the image-cycling behavior to actually engage.

No obvious source for sequence_json. This node consumes beat/shot data, it doesn't produce it - you need one of this pack's BPM or music-video sequencing nodes upstream to generate that JSON first. If you're just starting out with the audio-reactive family, this is a good first node to wire up once you already have working beat data, precisely because its output is so easy to eyeball for correctness (a flash that visibly lands off the beat tells you your upstream detection needs tuning before you invest in anything more elaborate).

Cycling images run out before the clip ends. If your images batch is shorter than the number of beats in the sequence, the node has to reuse images - check your source batch size against your expected beat count if the cycling looks repetitive sooner than expected.