Actually cdck is a simple program to verify CD/DVD quality. The known
fact is that even if all files on the disc are readable, some sectors
having bad timing can easily turn into unreadable ones in the future.
To get an idea about disc cdck reads it sector by sector, keeping all
reading timings and then tells you its verdict. Optionally it can write
timing table into text file usable by gnuplot(1) program, so you can draw
some graphs out of it.