Digital surround sound audio format developed by Sony for exclusive use in commercial theater installations. SDDS is a competitor of Dolby Digital and DTS in movie theaters, but SDDS is not available as a consumer product like Dolby Digital and DTS. SDDS signals are recorded on the outer edges of 35-millimeter film used in movie theaters as small dots that are optically read and translated into digital signals. he Sony system differs from Dolby Digital and DTS formats mainly in the number of channels it uses, seven in SDDS as opposed to 5.1 for the other formats. The seven SDDS channels are used for the left front, center left, center right, right front, right rear or surround, left rear or surround, and subwoofer. This differs from 5.1 formats in that SDDS uses a stereo pair of speakers in the place of a single, mono center channel as used by Dolby and DTS.