A METHOD TO CONTROL THE GENERATED BIT RATE IN MPEG-4 SHAPE CODING

摘要

In a digital video compression system that includes both a real buffer of size Bmax, and a smaller virtual buffer of size Bvirtual, a method for controlling the generated bit rate of compressed video information to keep within the maximum buffer capacity is disclosed. The method includes the steps of (a) receiving blocks of digital information (b) determining whether a current block can be compressed by one of one or more shortcuts and using the shortcut if possible; (c) if the current block cannot be compressed with any shortcut, determining whether the virtual buffer capacity will be exceeded if the current received block is compressed only by arithmetic coding and using only arithmetic coding if possible; (d) if the current block cannot be compressed with any shortcut and the virtual buffer capacity would be exceeded with only arithmetic coding, determining whether the virtual buffer capacity will be exceeded if the current block is compressed with both downsampling and arithmetic coding and using both downsampling and arithmetic coding if possible; and (e) if all else fails, compressing the current block with a default mode of compression even if the virtual buffer capacity is exceeded with such compression.