Mid-side stereo

Mid/side stereo-coding calculates a "mid"-channel by addition of left and right channel (l+r)/2 and a "side"-channel (l-r)/2. with more mono-like signals one can use less bitrate to encode the side-channel, so that the overall- bitrate will be less than encoding the left and right channel. Unlike intensity stereo which destroys phase information, mid/side coding keeps the phase information pretty much intact. Correctly implemented mid/side stereo does very little or no damage to the stereo-image and increases compression efficiency either by reducing size or increasing overall quality.