Digital Is Digital As long as one appreciates the limits of the point, it's an important point to make: a digital signal is just a string of ones and zeros. When a digital signal gets through a cable, and is interpreted correctly at the other end with no dropped bits, the result is no loss of information, and hence no loss of picture or sound quality. The signal may have suffered a great deal of degradation along the way from multiple causes; there may have been EMI, RFI, intrapair skew, interpair skew, return loss, rounding from capacitance, attenuation, anything - but if the bitstream gets read correctly at the end of the process, none of that degradation makes one bit (either figuratively or literally) of difference.

Now, that point often gets made into something it is not. People will sometimes claim that cable quality does not matter. The truth is more like this: if a particular cable, regardless of price and internal quality, delivers the signal in condition to be accurately read, no increase in cable quality will make things any better. However, if the cable does NOT deliver the signal in good condition, it is entirely possible that a better cable (which may or may not be more expensive) may fix the problem. This is so because, while it may seem a simple matter to deliver a series of ones and zeros by switching a voltage up and down, things get pretty funky at ultra high frequencies, and electricity does some strange and not always obvious things when one tries to run high-speed signals.