I made a CTF challenge for this year's BSidesSF CTF where players were given a CDDA audio file (just raw PCM samples) which when burned on a CD-RW would produce an image of the flag. (The idea was not for them to burn the audio, since they'd need to guess my exact CD-RW or else they wouldn't get an image readable enough to be useful. Instead they were supposed to invert the process in software and simulate what a burned disk would look like, in a way that let them adjust disk parameters rapidly until they had a readable image.)

The challenge took me a few weeks to make because "calibrating" a disk (determining the geometry of the pregroove) is incredibly sensitive.

After the CTF I tried really hard to make a repeatable calibration process with the intent of building something releasable. I even ended up measuring the details on every CD-RW and CD-R I could buy on Amazon.

But despite trying very hard, I never did make calibration patterns that were reliable enough that I felt like other people would be willing to go through the process.

It seems someone else has succeeded where I failed. Great to see!