Thus, to deliver full-screen broadcast quality video on a computer we would need a data throughput rate of at least 30MB per second. Since few desktop computers can deliver data at even half that rate, we clearly need a way to reduce the data throughput. When working with CD-ROMs or video destined for the web, data rates are much lower still. Frame Rate One of the most common methods of reducing the size of video files is to reduce the frame rate. 15 FPS is not uncommon, though lower rates are also sometimes workable.
Key frames contain an entire image.
Delta frames only contain data that has changed from the previous frame. The frequency of key frames is specified at compression time. Spatial compression is fast but is not as efficient as temporal compression. Temporal compression results in much smaller files while preserving quality, but is much slower than spatial compression. Some temporal compression schemes require special encoding and decoding hardware.