MEDIASTUDIO PRO USER GUIDE400just a few. The main reason for choosing 8-bit over 24-bit is that you cancontrol the range of colors that appear in an 8-bit file by using a colorpalette. This ensures that your video will display equally well on machinesrunning in 256 color display modes (often the requirement for thoseseeking to distribute video on CD-ROM or over the Internet).Understanding video compressionWhile frame rate, frame size and data type all contribute to controlling thetransfer rate, the real savings come from effective use of compression. Ingeneral, there are two types of compression used in the digital videoworld: spatial (intraframe) and temporal (interframe). By combiningthese methods, video files can be saved at a fraction of the size requiredfor their uncompressed counterparts. For example, compression schemes,such as MPEG, first compress the images in certain frames of a video byfinding repeated or similar patterns in the image. Then, the compressionmethod refers to preselected frames, (key frames) and creates baselinedata to compare against the information in the following frames. Thistime, the compression method seeks differences from the previous frameand discards everything else. It is for this reason that videos that use alimited number of colors and easily identified patterns, such as cartoons,tend to compress very well, while those with much greater colors andmore random patterns, such as live video recordings, require larger filesizes.Motion JPEGThe JPEG compression scheme works by compressing each frame in avideo sequence. It is not the most efficient in regard to file sizes, but bycompressing every frame individually, it offers the best quality and is thescheme of choice for people wanting to output back to video tape orbroadcast. To do this, however, you will need a lot of storage space and ahigh-end video capture board that can handle large amounts of data and
