Dolby Stereo

Dolby Stereo is a 1975 imported by the company Dolby analog Lichttonformat for movies. The first published with this sound standard film was A Star Is Born.

Four channels ( Left, Center, Right, Rear) here are matrixed in a dual optical sound that are dematrixed back into four channels when playing back from the cinema processor.

For noise reduction required the compander Dolby A or Dolby SR is used. Accordingly, the technically correct name of the format Dolby Stereo or Dolby Stereo A SR. For several years, the optical sound is produced exclusively with the latter variant.

The digital development called Dolby Digital, which has found its way into the home.

Each contains manufactured today feature film, independent of the digital sound tracks, a stereo Dolby SR sound track to which the projector automatically switches if the digital audio can not be read in sufficient quality or the cinema does not have a digital audio system. This will be heard by a sudden change in the dynamics of sound for the audience.

The version for home users is called Dolby Surround that, but not the noise reduction involves the same Matrizierungstechnik.