When selecting a frame size, it is best to adhere to current standards that reflect the aspect ratio of television. Some of the available standards for digital video in terms of pixels include 320x240, 240x180, and 160x120. The frame rate sets how many frames of video are captured or played back per second. The selection of frame rate should be based on the amount of action in the picture. Current applications are capable of achieving rates of up to 30 fps, the current standard for American television.
Video compression begins by reducing the amount of information within an individual frame.
Typically this is done by exploiting similarities between adjacent pixels and using smaller code words to encode a block of similar pixels. Once individual frames have been reduced, the compressor seeks a way to capitalize on redundancies between consecutive frames. If frame differencing is employed, the resulting data stream will contain only the differences between some reference frames. Decompression is achieved by reversing the process, and is often much quicker. There are certain aspects of frame differencing that can affect picture quality and movie file size.