Both analog and digital information can be compressed—made to fit into a smaller bandwidth than it would normally occupy. But compression of digital data works much better—from the perspectives of both quality and efficiency. Essentially, there are two kinds of digital compression: content-based and noncontent-based.
Content-based means that the compression scheme understands the content it is working with and adjusts the compression to the special characteristics of the data. The best example, a standards-based approach, is that of the Motion Picture Experts Group (MPEG). The MPEG standards, the widely used MPEG-1 and the more powerful and currently ascendant MPEG-2, were developed to deal with the ...