https://en.wikipedia.org/wiki/Blu-ray#Hard-coating_technolog...
Audio on scratched CDs can sometimes be cleanly ripped and repaired with the cdparanoia program. I don't know anything that does this with DVDs.
https://www.xiph.org/paranoia/
CDs and DVDs can also be refinished by equipment that grinds down and polishes the plastic, assuming the data layer is intact beneath it. This cannot be done with Blu-ray media, because of the altered surface chemistry.
https://en.wikipedia.org/wiki/Blu-ray#Hard-coating_technolog...
Audio on scratched CDs can sometimes be cleanly ripped and repaired with the cdparanoia program. I don't know anything that does this with DVDs.
https://www.xiph.org/paranoia/
CDs and DVDs can also be refinished by equipment that grinds down and polishes the plastic, assuming the data layer is intact beneath it. This cannot be done with Blu-ray media, because of the altered surface chemistry.