If you're familiar with Moire patterns and/or the Nyquist theorem, it's basically ensuring that we don't have too much information for the sampled channel (ie: the pixels that make up the line). The symptom of "overloading the channel" is shimmering and/or moire patterns -- the same sort of artifacts you'd get while trying to record high frequencies at a very low sampling rate.
If you're familiar with Moire patterns and/or the Nyquist theorem, it's basically ensuring that we don't have too much information for the sampled channel (ie: the pixels that make up the line). The symptom of "overloading the channel" is shimmering and/or moire patterns -- the same sort of artifacts you'd get while trying to record high frequencies at a very low sampling rate.