Dolby Surround is the earliest consumer version of theatrical Dolby Stereo that was introduced in 1982. The format entered the market when home video recording formats like Betamax and VHS were introducing Stereo and HiFi capability. It is the earliest version of Dolby’s multichannel analog film sound decoding format introduced by Dolby Stereo.
Dolby Surround is used to distinguish between home stereo that has only two channels, and theater surround (Dolby SR) that has four channels of audio. The production of a Dolby Stereo or Dolby Surround soundtrack instigates the matrix-encoding of four channels of audio information onto two audio tracks. The left, right, center and mono surround channels are matrix-encoded onto two audio tracks. This stereo information is then carried on stereo sources like videotapes, laserdiscs and television broadcasts. To recreate the original four-channel surround sound, the surround information can be decoded by a processor. The information still plays in standard stereo or mono, in the absence of decoder.
The technology used for decoding the monaural surround soundtrack is virtually the same as that used by a Dolby Surround decoder. This enables the transfer of Dolby Stereo encoded films to the stereo soundtrack with little change. The advantage of this technology is the reduction in costs of re-recording of the audio of a film to video. This was also assisted by the inclusion of Dolby B decoder in the design. The technology was updated and renamed as Dolby Pro Logic in 1987.