sentences:  SDDS's much-touted eight track playback capability never quite caught on, as it required that a separate eight channel sound mix be created in addition to the six channel mix that is needed for SRD and DTS, an additional expense for the studios.Out of the 1,400 plus films mixed in SDDS, only 97 of them to date have been mixed to support the full 8 channels, most of them Sony (Via Sony Pictures/Columbia/Tristar) releases.Because of the added installation expense, the majority of SDDS installations are 6 channel (5.1) installations, as opposed to 8 channel (7.1) installations.