I have recently bought an HD set and will be having a new HD dish installed next week. I have read that the HD DVR that I will be using is capable of MPEG-2 and MPEG-4 broadcasts. I am totally new to HD and have little idea as to what these are. I am assuming they have to do with the compression of the signal, but maybe someone could give me a detailed explanation as to exactly what they are and how they might effect the broadcasts. Thanks.