Delithic asked:

HD DVDs use some sort of extra compression format to increase the amount of data over regular DVDs. Blu Ray used a different laser paradigm that can read things closer together. I am not talking about a player that plays both, I am talking about using the compression scheme on the HD DVDs on the smaller wavelengh Blu Ray disks to make them higher capacity. I am not really sure exactly how the HD DVDs work out their increased capacity.

Kyle