Digitising CDs (a.k.a. using your phone as an image scanner)

11 JNRowe 6 7/28/2025, 4:47:46 AM hadess.net ↗

Comments (6)

dvh · 52m ago
I recently used ffmpeg to undo perspective from the image you just provide 4 corners coordinates and it produced straightened image:

    ffmpeg -i input.jpg -vf "perspective=x0=784:y0=396:x1=2396:y1=397:x2=684:y2=2479:x3=2610:y3=2467" output.jpg
voidUpdate · 39m ago
Is there anything FFMPEG cant do?
sandbach · 34m ago
I thought this was going to be about recovering data from a CD from just a photo of the shiny side. Could that be possible?
makeitdouble · 2m ago
CD data pitch would be 700nm, and it seems that camera sensors have a pixel pitch at the same order of magnitude.

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...

https://letmaik.github.io/pixelpitch/

schoen · 15m ago
I don't think so.

The 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.

jackweirdy · 10m ago
Does it have to be one photo? If you reproduced a spinning drive but with the camera positioned to see half of the spinning disc, I wonder if it could capture the "stream" of pixels in one arc of the spinning disc