Video Resolution

Here's a chart showing the differences in resolution between the various current video standards. Note that DVDs max out at 480p, which is the lower left box. NTSC standard is 29.97 frames per second (fps).

 

The European PAL standard is the next box. This runs at 25 fps.

 

Your "High-def" cable TV signal is either 720p or 1080i, which amount to the third box (1080i is the size of the largest box but it's interlaced, only half the picture gets redrawn each cycle so it's not as good as 1080p). This is typically 29.97 fps (often called 30 fps but it's really not).

 

Almost all Blu-rays are encoded at 1080p, which is the largest box. The entire 1920x1080 picture is redrawn every cycle. Blu-rays can be encoded at various frame rates and this affects quality too because while the TV standard in America is 29.97 fps, movies are almost all shot at 24 fps. The conversion that has to be done to play 24 fps material on a ~30 fps device is called "pulldown" and involves padding frames and playing some multiple times in a specific pattern such as 3:2 pulldown which is 2-3-2-3-2-3. In practice it almost always negatively affects picture quality due to the interpolation needed...especially in scenes with motion. If you have a television that can correctly reproduce the cadence of a native "24p" Blu-ray (one that is encoded on disc at 24 fps), the pulldown step is not needed and you get perfect movie motion, just like in the theater.