Dolby Laboratories

::Dolby redirects here. "Dolby" may also refer to the engineer Ray Dolby or the musician Thomas Dolby

Technologies

• Dolby Stereo or simply Dolby Analog is the original analog optical technology developed for 35 mm prints and is encoded with four sound channels: Left/Center/Right (which are located behind the screen) and Surround (which is heard over speakers on the sides and rear of the theatre) for ambient sound and special effects.
• Dolby Analog SR or simply Dolby SR (Spectral Recording) is a professional four-channel noise reduction system in use since 1986, which improves the dynamic range of analog recordings and transmissions by as much as 25 dB. Dolby SR is utilized by recording and postproduction engineers, broadcasters, and other audio professionals. It is also the benchmark in analog film sound, being included today on nearly all 35 mm film prints. On films with digital soundtracks, the SR track is used in cinemas not equipped for digital playback, and it serves as a backup in case of problems with the digital track.
• Dolby Digital (AC-3) delivers digital audio via six discrete channels (referred to as "5.1"). The three front channels (Left/Center/Right) deliver crisp, clean dialogue and accurate placement of on-screen sounds, while twin surround channels (Left Surround/Right Surround) wrap around the audience and immerse them in the action. The LFE (Low-Frequency Effects) channel delivers real impact for explosions and other effects that can, literally, be felt as well as heard. Used in DVDs and cinemas and on digital satellite (DBS), cable, and DTV and HDTV terrestrial services. It can also be used to deliver 5.1 surround radio services.
• Dolby Digital Surround EX introduces a center rear channel to the 5.1 playback format of Dolby Digital.
• Dolby Digital Plus is an audio codec based on and compatible with Dolby Digital, but more advanced. The DVD Forum has selected Dolby Digital Plus as a standard audio format for HD-DVD video. Dolby Digital Plus can also be applied to limited bandwidth environments such as broadcast television.
• Dolby A/B/C/S-Type NR, noise reduction systems for tapes and analog cassettes, see Dolby noise reduction system
• Dolby Pro Logic, Dolby Pro Logic II, Dolby Pro Logic IIx
• Dolby E is a professional coding system optimized for the distribution of surround and multichannel audio through two-channel postproduction and broadcasting infrastructures, or for recording surround audio on two audio tracks of conventional digital video tapes, video servers, communication links, switchers, and routers. The Dolby E signal does not reach viewers at home. It is decoded back to baseband audio just prior to the final DTV transmission and then re-encoded into the final audio format specified by the various DTV emission systems.
• Meridian Lossless Packing is a true "lossless" coding system specified for DVD-Audio that compacts PCM data with bit-for-bit accuracy, unlike "lossy" perceptual coding systems such as Dolby Digital. MLP effectively doubles disc space without affecting the quality of high-resolution PCM audio, making it possible for DVD-Audio discs to carry both stereo and multichannel mixes of the same program. All DVD-Audio players are equipped with MLP decoding, while its use on the discs themselves is at their producers' discretion.
• Dolby HX Pro Single-ended system used on high-end tape recorders to increase headroom. The recording Bias is varied with respect to the high frequency component of the signal being recorded. No coding/decoding is used.
• Dolby TrueHD is Dolby's next generation lossless coding technology. It offers bit-for-bit sound reproduction identical to the studio master. Over eight full-range 25-bit/96kHz channels are supported, along with the HDMI interface. It has been selected as the mandatory format for HD DVD and as an optional format for Blu-ray Disc.