There are two primary ways to deliver a surround sound signal. The older analog matrix technology works by mixing (matrixing) multiple channels into two main channels; the matrixed information then has to be decoded into the original channel configuration. The newer digital discrete technology keeps all the channels separate from start to finish. Discrete surround sound is superior to matrix surround. Surround effects are clearer and more distinctly positioned.
The most common matrix surround sound formats are Dolby Surround (left, right, and surround channels); Dolby Pro Logic (left, center, right, and surround); and the newer Dolby Pro Logic II and Dolby Pro Logic IIx, which are designed to simulate surround sound from two-channel sources.
The most popular discrete surround sound format is Dolby Digital, which can reproduce up to 5.1 channels: left front, center front, right front, left surround, and right surround, plus a separate low frequency effects (LFE) channel. Dolby Digital can also reproduce mono (1.0) and stereo (2.0) soundtracks.
DTS is a competing 5.1 format that offers slightly better sound due to higher data sampling rates.
Dolby Digital EX adds one or two rear channels behind the normal surround channels, for 6.1- and 7.1-channel configurations. Matrix technology is used for the rear channels.
DTS ES is a similar 6.1/7.1-channel format, using matrix technology for the new rear channel(s). DTS ES Discrete is different in that it adds a single rear channel on a discrete track.