Yup, the correct signal might not get through if you don't have perfect shielding. And a speck of dust on a CD could theoretically ruin a whole song. That's wh

Yup, the correct signal might not get through if you don't have perfect shielding. And a speck of dust on a CD could theoretically ruin a whole song. That's why CDs (and cellphones, modems, and countless other digital devices) use channel encoding.[1] That way you don't have to have a perfectly noise-free signal to reconstruct the original information. I don't know that many specifics of the DVD or Blu-Ray standards, but I'd put money on them using Reed-Solomon or something similar. [1] http://en.wikipedia.org/wiki/Reed-Solomon_error_correction#Data_storage http://en.wikipedia.org/wiki/Reed-Solomon_error_correction#D... (Edit: forgot footnote)