#Dolby #Surround #Pro #Logic
The format Dolby Surround, conceived in 1982 by Dolby Labs, is the first digital sound coding system to add an additional channel to the two channels of the stereo format. This supplementary channel, called “surround” allows to add an additional dimension to the sound (the English term “to surround” means “to surround”).
The 3 channels encoded according to the format Dolby Surround they are transported through the two traditional stereo channels in order to offer compatibility with the existing material. Thus, a decoder is necessary to be able to explore the 3rd channel mixed discreetly with the first two.
The surround channel has a maximum concurrent bandwidth of 7 kHz and a delay time of around 20 min in order to improve the realism of the effects.
Equipment with a Dolby Surround decoder usually has the following logo:
Dolby Surround Pro Logic
The format Dolby Surround pro Logic (usually called Dolby pro Logic), which appeared in 1987, is an improvement on the Dolby Surround format, which adds a fourth channel to the 3 channels of Dolby Surround, allowing it to constitute a central channel designed to reproduce the voice of the actors.
Thus, a Dolby pro Logic system comprises the following elements:
- Dual side columns in front
- A central column
- Two surround back speakers (in mono)
It also brings improvements in terms of quality of sound restitution and adjustments.
The equipment, capable of decoding an audio source encoded with the Dolby pro Logic method, usually bears the following logo:
Dolby Pro Logic II
O Dolby pro Logic II, created in August 2000, allows an artificial reconstitution of a 5.1 sound environment thanks to computer treatments applied in a stereo source (2.0) or Dolby Surround (3.0 / 4.0 / 4.1).
The devices, capable of decoding an audio source encoded with the Dolby pro Logic II method, usually display the following logo:
The Dolby Surround and Dolby pro Logic systems are now outdated, since the emergence of Dolby Digital and DTS. However, they remain useful to reconstruct a 3D sound from a stereo source.
Dolby Pro Logic IIx
The standard Dolby pro Logic IIx, developed in 2003, allows to artificially reconstitute a 6.1 or 7.1 sound environment from a stereo source. It proposes several sound environments according to the type of use to be carried out:
- Movie for reading movies,
- Music for CD reading ‘sudio,
- Range for video games.
Equipment capable of decoding an audio source encoded using the Dolby pro Logic IIx method generally bears the following logo: