Joint stereo coding

As for the underlying audio coding methods itself the goal of joint stereo coding is to reduce the amount of information which is transmitted to the receiver without introducing audible artifacts. This is done by using the stereo redundancy and the irrelevancy of certain stereo coding artifacts. 

The matrixing done in M/S joint stereo coding is invertible. Without the quantization and coding of the matrix output the processing is completely transparent. 

The precedence effect describes the effect that sound sources are sometimes localized not according to the loudness of left versus right channel but on the origin of the first (not the loudest) wavefront. This time relationship between signals can be distorted by certain joint stereo coding techniques resulting in an altered stereo image. 

In terms of joint stereo coding techniques, Layer 3 supports a combination of M/S coding (broad band) and intensity stereo coding (see [Herre et al., 1992]). 

Additionally, some of these systems exploit the significant redundancy between stereo channels by a technique known as joint stereo coding. Once the common information between left and right channels of a stereo signal has been identified it is only coded once, thus reducing the bit rate demands yet again. 

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