DTS-ES (DTS Extended Surround) includes two variants, DTS-ES Matrix and DTS-ES Discrete 6.1, depending on how the sound was originally mastered and stored.DTS-ES Discrete provides 6.1 discrete channels, with a discretely recorded (non-matrixed) center-surround channel; in home theater systems with a 7.1 configuration, the two rear-center speakers play in mono. DTS-ES Matrix provides 5.1 discrete channels with a matrixed center-surround audio channel. DTS-ES commonly works on a matrix system, whereby processors that are compatible with the ES codec look for and recognize "flags" built into the audio coding and "un-fold" the rear-center sound from data that would otherwise be sent to rear surround speakers. This is notated as DTS-ES 5.1. Less frequently, DTS-ES data can be encoded with a discrete sixth audio channel (the rear-center), meaning that the audio data for the sixth channel is stored separately from the other information, and is not embedded or matrixed among other channels. This is notated as DTS-ES 6.1, as the center rear is completely discrete from the other channels. ES capable processors can recognize the discrete sixth channel, and play it back if connected to the necessary speaker(s). In contrast, Dolby's competing EX codec, which also boasts a center rear channel, can only handle matrixed data and does not support a discrete sixth channel. DTS-ES is backward compatible with standard DTS setups, so non-ES equipment which does not recognize the flags or with ES enabled equipment that lack the extra speaker connections, sound plays back in 5.1 as if it were standard DTS. Only a few DVD titles have been released with DTS-ES Discrete. Note: The center rear/surround channel is encoded and decoded in exactly the same way as center front. The center surround channel can be decoded using any surround sound processor by feeding the left & right surround signals to the processor inputs. Left-Center-Right surround is produced. This will work for a 'center surround' reproduction, whether the source material is explicitly 'encoded', as in DTS-ES, or 'hidden' as ambience in any 5.1 source: including DTS-ES 5.1 and Dolby 5.1.
