RVMB is a file type developed by Real Networks and stands for RealMedia Variable Bit Rate file. RMVB is quite similar to MPEG4 files and differs from the RealMedia format which encodes at a constant value. XVID and DIVX are other types of variable bitrate files. RMVB files are quite common in Asia but less prevalent in Europe and the Americas.
Variable bit rate files alter the amount of data for a given amount of time. This allows the bitrate to be increased for more complex elements of the file, and decreased for less complex parts. This means the storage requirements of the file are less with a negligible decrease in image and audio quality. The disadvantage of this type of file is that the encoding process is longer compared to a constant bitrate file.