MEDIASTUDIO PRO USER GUIDE398Inside digital videoThere are three components that go into the makeup of digital video: framerate, frame size, and data type. The frame rate refers to the number offrames that appear each second, while the frame size is the actual physicalsize of each frame. The data type determines the number of colors allowedto appear at one time. How you work with these three elements is deter-mined by the type of video capture board available and your preferredmethod of distribution. For instance, if you have a high-end capture boardand plan to output your data into a video tape, then you need the best qualitypossible, like 640x480, 30 frames per second 24-bit color, for NTSCdevices. If you have a less expensive capture board, and plan to output yourvideo in a CD-ROM or over the Internet, then your decision on the type ofvideo is determined by the machine or medium it will be played back from.This is because different machines and mediums have different abilities atmoving amounts of video data. This ability is referred to as the data rate,which measures how much data can be moved within one second.Working with the data rateThe problem with most venues where video is transmitted and viewed (e.g.DVD players, computer disc players, the Internet, etc.) is that they havetrouble moving large amounts of data continuously. The specifications of amajority of these devices give you an indication of how many kilobytes canbe moved at any one time. A DVD with a capacity of 4.7 to 17GB, has adata rate of approximately 600kbps to 1.3mbps. Compare that to theInternet where many people still operate with 56kb dial-up modems with adata transfer rate of less than 57.6kbps!Another point to consider is that while devices promote a specific datatransfer rate, very few can maintain that rate over an extended period. Assuch, if your video comes in just under 600kbps, it doesn’t necessarilymean that most DVDs can play it smoothly. There are four factors thataffect the data transfer rate for video files: frame rate, frame size, datatype, and compression.
