Lossy compression?
How are HD DVD’s encoded to produce the high quality video that they are able to display? It’s actually not as involved as you might think. Each film studio has digital master copies of the films that they produce. From that the video is read and compressed into the MPEG-2 format which effectively uses lossy compression to remove repeat and/or redundant video data. This often means areas of the screen that don’t change from frame to frame get removed. Depending on the level of compression the video quality may differ slightly, but most HD DVD Players will provide you with excellent video output due to the level of complexity of the video graphics module.