What does CBR mean?
CBR stands for Constant Bit Rate (or data rate) and VBR stands for Variable Bit Rate. These are the two main methods which can be used when encoding MPEGs. During CBR encoding the video stream is encoded using the same data rate, regardless of the complexity of the material being encoded. During VBR encoding the video stream is encoded using a data rate which varies depending on the complexity of the material. So during simple static scenes bits are conserved for use in the more complex fast-moving sequences. VBR encoding usually requires 2-3 passes (multi-pass encoding). During the initial playback passes the encoder analyses the video stream before encoding it on the final pass. VBR encoding produces the same quality as CBR encoding but at lower data rates, which result in smaller file sizes.
