WireItRight
home theatre installation and pre-wire services
What is HDTV?
High-definition television (HDTV)
Advantages of HDTV
Recording and compression
Blu-Ray
HD DVD
Dolby
What is
Dolby ?
Dolby A/B/C/S-Type NR: noise reduction systems for tapes and analog cassettes.
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 post-production 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 FM A noise reduction system for FM broadcast radio. Dolby FM used Dolby B, combined with 20 microsecond pre-emphasis. This system integrated into a small number of receivers, and was used by a few radio stations in the late 1970's and early 1980's. The system is no longer used, however.
Dolby Digital (also known as AC-3 and SR-D) 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. As the LFE channel only uses about one-tenth the bandwidth of the others, it is referred to as a ".1" channel, hence the designation "5.1". 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. It is matrixed out of the rear left and right channels, and so does not create true 6.1 sound.
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-E selected hardware.Dolby E is a professional coding system optimized for the distribution of surround and multichannel audio through two-channel post-production 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.
Dolby Headphone is technology that allows for simulated 5.1 surround sound in a standard pair of headphones.
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. It does nothing to the actual audio that's being recorded, and doesn't require a special decoder. Any HX Pro recorded tape will have, in theory, better sound on any deck.
Dolby Pro Logic, Dolby Pro Logic II, Dolby Pro Logic IIx
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. This technology also employs A-type or SR-type noise reduction, listed above with regards to analog cassette tapes.
Dolby TrueHD is Dolby's next generation lossless coding technology. It offers bit-for-bit sound reproduction identical to the studio master. Over seven full-range 24-bit/96kHz discrete channels are supported (plus a LFE channel,making it 7.1 surround) 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. Theoretically, Dolby True HD can support more channels, but this number has been limited to 8 for HD DVD and Blu-ray.
