Dolby Digital EX, DTS ES and 6.1 surround (Cut and paste)
Dolby Digital EX, and DTS-ES. This decoding method first came to light with the theatrical release of Star Wars Episode 1. Immediately, the home theater industry spoke up about this format. Many home theater enthusiasts complained about the need to purchase new equipment while the industry started making "EX Compatible" equipment. DTS jumped on board with DTS-ES, a similar effort.
This decoding method works by taking the two rear channels of a Dolby Digital 5.1 soundtrack and run them through a Dolby Prologic-like decoder. This builds a third channel of sound from the two surround channels, which is sent to one or two amplifiers and speakers positioned behind the primary viewing position.
There is no standard that say's EX is one or two speakers but the general rule of thumb is 2. 7.1 adds a rear center.
