The goal is to recover the image produced by an oscilloscope from the sound it emits.
There’s a project entirely dedicated to this type of “music”: Oscilloscope Music
And they have open-source software that lets you convert audio to an oscilloscope waveform: Oscilloscope! and on Github. But the Linux version is too old, so I couldn’t get it to work.
Fortunately, I found another project of this type: m1el/woscope: WebGL-powered oscilloscope
And this one is much more stable. Once installed and launched with:
npm install
npm run demo
All we have to do is put our file (converted to .ogg using Audacity) in the woscope/woscope-music directory and go to:
http://localhost:9966/?file=oscillart.ogg
Then we can read the flag:
FCSC{vector_flag_9739}
And that’s it, we’ve got our flame 🔥 !