FL Audio Envelope Visualizer

Before you wire an audio envelope into brightness, saturation, speed, or glow effects and burn a render on it, it helps to actually see the curve you built. FL_Audio_Envelope_Visualizer is purely diagnostic - it doesn't touch your footage at all, it just turns an envelope JSON into a grayscale flipbook so you can watch it play before trusting it to drive something real.

How it works

It reads envelope_json - the ADSR-style per-frame curve produced by FL_Audio_Reactive_Envelope, or any node in this pack that outputs that same shape of data - and renders one grayscale frame per envelope sample, where pixel brightness directly represents the envelope's value at that frame. A curve that spikes hard on every kick and decays slowly reads as a flipbook of bright flashes fading to gray; a curve with fast attack and release reads as sharper on/off flickers. Watching that flipbook is a much faster way to catch a mistuned attack/decay/release setting than staring at raw JSON numbers.

The inputs and outputs that matter

Required: envelope_json - the only thing you need to supply.

Optional: width/height (default 512), intensity (0.1–5, default 1) - scales how strongly the envelope value maps to brightness; push it up if a mostly-quiet envelope is rendering as near-black and you want the subtle variation visible, invert - flips the mapping so a low envelope value reads bright instead of dark.

Output: frames - a grayscale IMAGE batch you can preview directly.

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. No heavy dependencies for this node specifically - it's straightforward pixel drawing from a JSON curve.

Common issues & troubleshooting

Everything looks flat/gray. Your envelope's actual value range is probably small relative to what intensity: 1 maps cleanly to visible brightness variation - raise intensity before assuming the envelope itself is broken.

Flicker looks too sharp or too smooth compared to what you expected. That's not this node's fault - it's rendering exactly what's in the envelope JSON. If the pulse timing is off, the fix is in FL_Audio_Reactive_Envelope's attack/decay/sustain/release settings (or FL_Audio_Drum_Detector's sensitivity, further upstream), not here. Use this visualizer to confirm where in the chain the timing actually goes wrong before you start adjusting knobs blind.

Skipping this step entirely. It's tempting to wire an envelope straight into a reactive effect and just look at the final rendered video, but a mistuned envelope is much easier to spot in this node's flat grayscale flipbook than buried under color, motion, and content in the final composited result - five seconds here saves a re-render later.