Digitising CDs (a.k.a. using your phone as an image scanner)
hadess.net
hadess.net
ffmpeg -i input.jpg -vf "perspective=x0=784:y0=396:x1=2396:y1=397:x2=684:y2=2479:x3=2610:y3=2467" output.jpgThe total data on a CD-ROM including the error correcting redundancy exceeds 800 MB, or 6.4 Gb.
If you could imagine getting 1 bit from the optical disc per pixel (which is way too optimistic physically), you would need a 6 gigapixel camera focused super-precisely at the disc surface.
Looking at the problem from a different angle, Wikipedia says the features that store the data on the disc surface are about 800 nm (or about a micrometer) long. So to photograph them, you'd want to have pixels ideally smaller than a micrometer on each side. It's easy to check that an ordinary camera isn't achieving that kind of resolution without adding on external magnifying equipment.
The optics of a CD-ROM drive are optimized for something pretty different than the optics of a camera. But if you made enough tweaks and adaptations, sure, the data is ultimately there and can be captured by a different kind of sensor than the one it was designed for. It would be a cool project.
I'm mostly just pointing out that adapting your camera to successfully capture billions of sub-micrometer features isn't that trivial.
Ignoring the lens resolution you'd need for a near 1 to 1 rendering at that size, any hand movement or misalignment would also be catastrophic.
That sounds like a crazy dream until we get to sensor in the peta pixel range ?
https://www.researchgate.net/figure/CD-DVD-Blu-ray-disc-data...
On the other hand I'm still puzzled why there are no homebrew projects for a dumb dumping device that simply reads all the data on a cdrom, error correction, subchannels completely raw. There are a lot of CDs with a very weird data structure (Console Games, Early Copy Protected pc games, AKAI sample discs, some Hybrid Macintosh discs, in other words anything not using the iso9660 standard) which are at risk of Disc Rot[1], and simply storing them as Iso or Bin/Cue files (including proprietary variants like Alcohol 120%/Daemon Tools mdf files) is basically useless both for archival and real world usage purposes.
I think you'd have to write a custom firmware for one specific drive for that. That information is simply not exposed outside the device itself on standard drives, which is what makes it effective for copy protection.
A more pragmatic solution would be to use an ESP32 or an RPI2040, wire them to a "donor" cd drive and then implement just the most basic MMC commands to make sense of the disc layout and save to disk the binary stream.
I'm pretty sure I'm missing something extremely obvious given the lack of similar attempts; wouldn't be surprised if not a single readily available programmable microcontroller on the market has the necessary bandwidth for this task.
But is not a true raw dump like we see in a bunch of other media preservation projects.
I think this would be an improvement to the OP's process: Print a thick black rectangle sized such that the contour's inner edge is slightly larger than the CD. Use the phone to take a picture and deskew it - the scanner should "catch" on the inner contour. Repeat with all other CDs. Finally, load the images onto the computer and run batch processing on them using your raster image editor to trim whitespace. This way, you'd keep manual labour to a minimum.