[Build-A-Bump]

The idea

I was making custom Adult Swim style bumps in After Effects and despite how simple the format is, it was more friction than it should have been. Build-A-Bump is a browser tool that makes it as easy as it should be: black background, white text, a piece of music, done.

It was also a chance to build something with the Audius API that isn’t just another streaming client. Most Audius integrations are music players. This is a creative tool that happens to pull music from Audius, which felt like a more interesting use case.

How it works

The format is deliberately constrained to match the Adult Swim bump format. Black background, single font, hard cuts only, white text, up to fifteen seconds of audio from any Audius track. No transitions. No background images. No free-form element positioning. The constraints aren’t limitations. They’re what keeps the output looking right.

You add text and images to a timeline, pick a track, choose an aspect ratio (16:9, 1:1, 9:16, or 3:4), and render an MP4 in the browser. The export pipeline runs through WebCodecs and mp4-muxer. The result is a broadcast-ready H.264 file, exported directly from the page.

The timeline shows the full waveform of the Audius track. Drag the waveform to pan the audio and fine-tune timing. The region outside dims. There’s no “audio offset” setting. The visual is the control.

First-time users land on a working bumper with real content and a track already selected. Projects autosave locally. Export a .bump file to move a project between browsers or keep a backup. The file is plain JSON, so you can also feed one to an LLM to iterate quickly.