There are a few main different types of surround sound formats which is widely used in the home cinema industry,and these are as follows.
DOLBY PRO LOGIC SURROUND SOUND
This format is the most widely used in the home cinema industry . This type of surround sound is made up from a analogue signal which is extracted from Television broadcasts, Video films, Laserdiscs and DVD's which are all sometimes encoded with this signal. This format is known as a four channel surround which means that it is made up of the following channels, Front left, Centre, Front right and Mono rears (two rear speakers but the same mono signal is fed to both of them).Also the rear channels only carry a limited band width ,unlike the front three channels which are full range.
DOLBY DIGITAL (AC-3) SURROUND SOUND
This format is becoming more widely used these days and is set to be the standard surround sound format of DVD's in europe. This type of surround sound is made up from a digital signal which can only be extracted from, Laserdiscs (ntsc format only which is the format used in the united states), and DVD's (all regions) which are usually encoded with this signal. This format is known as a 5.1 channel surround which means that it is made up of the following channels, Front left, Centre, Front right, Rear left, Rear right, Sub woofer channel (this is the .1 channel). All of the channels are full range channels with the exception of the sub woofer channel, This only handles the Low Frequency Effects (LFE). When comparing the two different formats ( pro logic vs AC-3) the difference is amazing ,Its like comparing nicam television broadcasts to mono broadcast, It is that much of a improvment. With dolby digital the entire surround effects are more clear and precise, The whole sound stage is more dynamic, And the explosions are more tighter controlled with a greater impact. The surround rear channels just come alive with effects on dolby digital because they are in stereo as opposed to mono, they send sound effects screeming past your left ear and then your right ear, it is just like being placed directly in the centre of the action.
DTS (DIGITAL THEATRE SYSTEM)
This format is said to be the best of the digital formats becuase the compression rate of the data which is stored on a soundtrack is less than dolby digital so the sound should be more life like and the most accurate of all the surround sound formats. DTS isn't as widespread as dolby digital though, but it is increasing all the time in cinemas and is being built into more electrical products.The features of DTS is the same as dolby digital with the 5.1 channel surround . The DTS signal is extracted from Laserdiscs mainly , DVD's (region 1), and there are a few music cd's on the market with DTS.