Digital videos are compressed more than once during the production process.

It's best to create small movies at medium compression, and then when finished, they can be compressed more.

Common JPEG algorithms (and chips) can compress and decompress in 1/30 second.

This is fine because video is played at 30 frames/second or less!

But digital video needs storage reductions of 1/100 or more, and JPEG does not produce a good picture at these compressions.

Also, JPEG compresses within a frame (intraframe), and further compression can often be achieved by compressing between frames (interframe).

The Moving Pictures Expert Group ( MPEG ) compression algorithm compresses by as much as 1/200 with high quality picture (and sound).

While JPEG takes more or less the same amount of time to compress and decompress, the speed of MPEG compression varies.

Like JPEG, MPEG compresses by removing redundant information.

MPEG compressed movies run faster and take less space.

JPEG performs just intraframe compression

It removes redundant information from within a single frame.

MPEG doesn't even store the information that doesn't change from frame to frame (background) once it has compressed and stored it. It samples every 15 frames (i.e., every half second).