The most contributing factor for high CPU useage is what type of video the dream was made from, MPEG2 or WMV. Mpeg will normally have better quality for less CPU at the cost of larger file size.
Then it breakes down to the bit rate, frames per second and resolution.
Zub, you are correct in the sence that if a dream has alot of motion the author will need to bump the frame rate up to 30 to keep the loop from being as noticeable. That being the case it will usually use more CPU. But, if a dream is done at 30 fps and at a lower bit rate it can use less cpu than a dream at 25 fps and a higher bit rate.
One thing about bit rate, the higher it is, the better the picture quality is.
Same goes for resolution.
All this makes it a balancing act for the author to get low cpu useage while trying to get a nice quality picture.
