Joint Stereo Coding

Obviously, stereo sound has twice as much information as mono. Yet, the information on one channel of stereo is often identical to the other. For example, a bass guitar that 'appears' centered will have the same data on both left and right stereo channels.

Joint Stereo carries identical information (like the bass guitar above) in one channel, and the other channel carries the difference (anything left over). This allows for a more efficient allocation of bits; however, in practice joint stereo is only used with low bitrate signals. In other words, this step may not be included, and whether it is included or not depends on the encoder.