What does a video codec do?
Anybody who has played-back a movie on their computer knows that the video is choppy and low resolution. The reason is that current PC technology simply can’t handle the amount of data required to display uncompressed full-screen video. To understand why, we just have to look at the amount of data contained in a video clip. If we want to record a standard video signal for digital playback, we have to digitize it at about 640×480 pixels/frame. At a refresh rate of 30 fps (frames per second), and true colour (16.7 million) we would be pumping 640x480x30x3 = 28 Mbytes/s through our computer. At that data rate, a 650 Mbyte CDROM would hold only 23 seconds of video! CDROM reader and hard drive technologies don’t allow us to transfer data at such high rates, so in order to display digital video it is compressed for storage. Compressed video streams are read from a hard drive or CDROM, then are decompressed before being displayed. This decompression is very CPU intensive, and displaying the r
