Dolby Surround

Dolby Surround was the earliest consumer version of Dolby's multichannel analog film sound decoding format Dolby Stereo. It was introduced to the public in 1982 during the time home video recording formats (such as Betamax and VHS) were introducing Stereo and HiFi capability. The term Dolby Surround is used so as not to confuse theater surround (Dolby SR, which has four channels of audio) with home stereo, which has only two. Dolby Surround is the earliest domestic version of theatrical Dolby Stereo. The term also applies to the encoding of material in this sound format.

Technical details

When a Dolby Stereo/Dolby Surround soundtrack is produced, four channels of audio information (left, center, right, and surround) are matrix-encoded into only two channels. The surround information is carried on stereo sources such as VHS-HiFi, TV, DVDs, 35mm theatrical print optical soundtracks, or television broadcasts from which it can be decoded by a processor to recreate the original Dolby Stereo/Dolby Surround (left, center, right, and surround) mix. Without the decoder, the information still plays in standard stereo or mono.

Surround sound

Surround sound is a technique for enriching the sound reproduction quality of an audio source with additional audio channels from speakers that surround the listener (surround channels), providing sound from a 360° radius in the horizontal plane (2D) as opposed to "screen channels" (centre, [front] left, and [front] right) originating only from the listener's forward arc.

Surround sound is characterized by a listener location or sweet spot where the audio effects work best, and presents a fixed or forward perspective of the sound field to the listener at this location. The technique enhances the perception of sound spatialization by exploiting sound localization; a listener's ability to identify the location or origin of a detected sound in direction and distance. Typically this is achieved by using multiple discrete audio channels routed to an array of loudspeakers.

There are various surround sound based formats and techniques, varying in reproduction and recording methods along with the number and positioning of additional channels.

Dolby Digital

Dolby Digital is the name for audio compression technologies developed by Dolby Laboratories. It was originally named Dolby Stereo Digital until 1994. Except for Dolby TrueHD, the audio compression is lossy. The first use of Dolby Digital was to provide digital sound in cinemas from 35mm film prints. It is now also used for other applications such as HDTV broadcast, DVDs, Blu-ray Discs and game consoles.

In the cinema

Batman Returns was the first film to use Dolby Digital technology when it premiered in theaters in the summer of 1992. Dolby Digital cinema soundtracks are optically recorded on a 35 mm release print using sequential data blocks placed between every perforation hole on the sound track side of the film. A constant bit rate of 320 kbit/s is used. A charge-coupled device (CCD) scanner in the image projector picks up a scanned video image of this area, and a processor correlates the image area and extracts the digital data as an AC-3 bitstream. The data are finally decoded into a 5.1 channel audio source. All film prints with Dolby Digital data also have Dolby Stereo analogue soundtracks using Dolby SR noise reduction and such prints are known as Dolby SR-D prints. The analogue soundtrack provides a fall-back option in case of damage to the data area or failure of the digital decoding; it also provides compatibility with projectors not equipped with digital soundheads. Almost all current release cinema prints are of this type and may also include SDDS data and a timecode track to synchronize CD-ROMs carrying DTS soundtracks.

7.1 surround sound

7.1 sound is the common name for an eight-channel surround audio system commonly used in home theatre configurations. It adds two additional speakers to the more conventional six-channel (5.1) audio configuration. As with 5.1 surround sound, 7.1 surround sound positional audio uses the standard front, center, and LFE (subwoofer) speaker configuration. However, whereas a 5.1 surround sound system combines both surround and rear channel effects into two channels (commonly configured in home theatre set-ups as two rear surround speakers), a 7.1 surround system splits the surround and rear channel information into four distinct channels, in which sound effects are directed to left and right surround channels, plus two rear surround channels. In a 7.1 surround sound home theatre set-up, the surround speakers are placed to the side of the listener's position and the rear speakers are placed behind the listener. In addition, with the advent of Dolby Pro Logic IIz and DTS Neo:X, 7.1 surround sound can also refer to 5.1 surround sound configurations with the addition of two front height channels positioned above the front channels or two front wide channels positioned between the front and surround channels.

Dolby Laboratories

Dolby Laboratories, Inc., often shortened to Dolby Labs, is an American company specializing in audio noise reduction and audio encoding/compression. Dolby licenses its technologies to consumer electronics manufacturers.

History

Dolby Labs was founded by American Ray Dolby (1933-2013) in the United Kingdom in 1965. He moved the company to the United States (San Francisco, California) in 1967. The first product Dolby Labs produced was the Dolby 301 unit which incorporated Type A Dolby Noise Reduction, a compander based noise reduction system. These units were intended for use in professional recording studios.

Dolby was persuaded by Henry Kloss of KLH to manufacture a consumer version of his noise reduction. Dolby worked more on companding systems and introduced Type B in 1968.

Dolby also sought to improve film sound. As the corporation's history explains:

The first film with Dolby sound was A Clockwork Orange (1971), which used Dolby noise reduction on all pre-mixes and masters, but a conventional optical sound track on release prints. Callan (1974) was the first film with a Dolby-encoded optical soundtrack. In 1975 Dolby released Dolby Stereo, which included a noise reduction system in addition to more audio channels (Dolby Stereo could actually contain additional center and surround channels matrixed from the left and right). The first film with a Dolby-encoded stereo optical soundtrack was Lisztomania (1975), although this only used an LCR (Left-Center-Right) encoding technique. The first true LCRS (Left-Center-Right-Surround) soundtrack was encoded on the movie A Star Is Born in 1976. In less than ten years, 6,000 cinemas worldwide were equipped to use Dolby Stereo sound. Dolby reworked the system slightly for home use and introduced Dolby Surround, which only extracted a surround channel, and the more impressive Dolby Pro Logic, which was the domestic equivalent of the theatrical Dolby Stereo.