This evolved into Dolby Pro Logic, which could intelligently extract 5.1 surround sound from a regular stereo soundtrack. 1992's "Batman Returns" was the first film released in Dolby Digital format, ...

A digital audio encoding system from Dolby that provides four channels. Derived from the Dolby Stereo technology used in movie theaters, Dolby Surround was introduced in the early 1980s for video ...