Dolby Pro Logic
Dolby Pro Logic is an analog surround sound system developed by Dolby Laboratories, Inc. in 1986 for domestic use, based on their 1976 cinema system, Dolby Stereo. It decodes surround information from stereo sound, if present.
Suitable source programs encode four channels of sound on the ordinary stereo sound track by phase shift, called speakers.
In 2000, Dolby introduced Dolby Pro Logic II, which has a 'Music' and a 'Movie' profile (latter also suitable for games). Pro Logic II is basically an upgraded version of Pro Logic, adding the subwoofer and a second rear channel to the encoded information, giving it control over the full 5.1 channels used by surround systems nowadays. It is in particular quite frequently used by the current generation of videogames for ps2, xbox and gc, even though they also have digital outputs.
Dolby also defined Dolby Pro Logic IIx, which extends a 5.1 sound source to 6.1- or 7.1-channel output.
Dolby Pro Logic has been superseded by Dolby Pro Logic II. The former is considered to have comparatively poor channel separation and suffer from the bandwidth limits of the rear channel. Pro Logic II has been superseded by digital 5.1, 6.1 and 7.1 channel systems (such as Dolby Digital and DTS) offering full digital channel separation. However, Pro Logic II still has some advantages over the latter, particularly in providing 5.1 channels from two-channel stereo sources--broadcast media, for example--without requiring digital coax or optical connections.
Dolby Pro Logic vs. Dolby Surround
The difference between
