Pro Logic II

Dolby Pro Logic is a surround sound processing technology developed by Dolby Laboratories, designed to decode soundtracks encoded with Dolby Surround. Dolby Stereo was originally developed by Dolby in 1976 for analog cinema sound systems. The format was adapted for home use in 1982 as Dolby Surround when HiFi capable consumer VCRs were introduced; it was then replaced by the newer and improved Pro-Logic system in 1987. However, the term "Dolby Surround" is still used to describe the encoding technology or matrix-encoded soundtrack, whereas Pro Logic refers to the decoding technology and processor. It is the domestic equivalent of the theatrical Dolby Stereo technology used in movie cinemas in the 1970s and '80s. The two technologies are mostly identical but a change in marketing was needed so as not to confuse cinema stereo which is at least four channels of audio with home stereo which is only two. Thus Dolby Pro Logic is the consumer version of theatrical Dolby Stereo.