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Entries found for search: DOLBY

Dolby Digital™ : The 5.1-channel digital format created by Dolby Laboratories, first used in 1992 for "Batman Returns." In current usage, the term applies to both the Dolby 35mm theatrical format, which contains the data printed optically between the sprocket holes, and for video formats, such as DVD, laserdisc, and DTV. AC-3, as Dolby Digital was first called, used RF modulation of the digital signal onto one of the analog tracks, making it possible to fit an entire movie, along with the already existing digital tracks, onto a conventional laserdisc; a demodulator was needed to recover the audio back into a digital bitstream. The Dolby Digital format is a surround-sound, split-band, perceptual coding scheme. AC-3 was designed as a 5.1 multichannel format , using approximately 13:1 lossy compression, and is specified as the matrixing format for DVD and DTV. Also used in HDTV broadcasts, SR-D, and DSD cinema productions. Versatile, in that parameters such as bit-rate and number of channels can be tailored to particular applications, unique in that the data bits are distributed dynamically among the filter bands as needed by the particular frequency spectrum or dynamic nature of the program. Data rates vary from 32kbps for a single mono channel to as high as 640 kbps for 5.1 format. The data rate is 320kbps for film, 384kbps for laserdisc, and 384kbps or 448kbps for DVD, although the maximum throughput for the specification is 640kbps. Dolby’s current decoder can accept incoming data at 32kHz, 44.1kHz, or 48kHz sample rates, with bit depths of 16, 18, or 20 bits. The commercial competitor to the Dolby Digital format is DTS. See metadata, audio coding mode.

Dolby Fax : See ISDN.

Dolby Motion Picture 4:2:4 : A matrixed surround-sound system which combines multichannel LCRS audio in such a way that the encoded signal forms a stereo-compatible, two-channel format for recording and broadcasting. Originally developed in 1977 for "Star Wars," and now in wide use. As with any matrix system, it is impossible to completely recover the original multichannel signals with perfect isolation. The decoder disguises this problem through a steering process which emphasizes the signal emanating from its appropriate loudspeaker by canceling out a portion of the crosstalk in adjacent channels. See also free encoding, Pro Logic.

Dolby noise : The Dolby SR analog allows the comparison of the recorded Dolby noise on a tape to that generated by the decoder, with four continuous seconds of noise to identify the generator, and two 2-second sections of noise indicating that the monitoring is off-tape. This allows for confirmation of correct EQ settings as well as playback verification. The broadband reference signal used to correctly calibrate the different Dolby codecs is called Dolby noise. See Dolby tone.

Dolby noise reduction : A type of two-ended, dynamic noise reduction for magnetic tape recording and playback. The essential difference between a compander and the Dolby system is that the Dolby system is frequency-dependent. The compander was developed to reduce distortion. Dolby applies companding to frequency variations in addition to signal amplitude variations, adjusting gain as frequency changes. The Dolby-A and Dolby-SR systems are used for professional recording in studios. Consumer tape decks use either a Dolby-B or Dolby-C system. Dolby-B operates only at high frequencies and reduces tape hiss by about 10dB. Dolby-C works over a slightly wider frequency range, providing a noise reduction of up to 20dB. All of the Dolby systems operate on quiet passages, below levels of about -10VU. Very strong signals, such as over 60dB or at frequencies below 500Hz are not affected by the Dolby system because these signals are not degraded by tape noise. When the recorded signal is played back, the Dolby circuit reduces the accentuated high-frequency signals so that the frequency response of the record/playback system is flat, hence reducing also the high-frequency tape hiss, improving the S/N ratio of the taped music. See asperity, Barkhausen effect, compander, dbxcompander,dbx, spectral recording.

Dolby ProLogic™ : A four-channel perceptual coding scheme developed by Dolby Labs where an LCRS audio signal is converted into two channels of analog audio, then recovered to yield discrete left, center, right, and mono surround channels. This is a hardware version of their surround decoder originally developed for the Dolby Motion Picture 4:2:4 matrix surround-sound system, developed for the Star Wars picture in 1977. If a subwoofer is used, it is generally fed by lowpass-filtering a mix of the three front channels at the receiver.

Dolby SR™ : Dolby-SR is a complex type of two-ended, dynamic split-band, noise reduction compander system that outperforms Dolby-A, -B, or -C systems and also results in reduced distortion in most cases. This was developed as an upgrade to the professional Dolby-A, featuring an improvement in tracking accuracy and sliding bands, and closest to C-type noise reduction. S-Type noise reduction is the consumer analog. See SR.D.

Dolby SR.D™ : A system developed by the Dolby company for placing a digital audio soundtrack onto 35mm film, first used in 1992. The soundtrack includes a Dolby Digital mix, as well as an SR analog stereo optical track. The data are compressed and printed onto the film between the sprocket holes. See surround-sound, perceptual coding, Dolby surround-sound, spectral recording.

Dolby Stereo™ : The original Dolby Surround system which used four audio channels carried on a stereo optical track on 35mm film, using Dolby perceptual encoding. On 70mm film, six audio channels are recorded on discrete magnetic tracks laid onto the film. In the broadest and most common usage, the trademark that appears on movie prints, advertisements, and posters which means that a given film has been released in prints that employ Dolby A-Type noise reduction encoding. Beginning in 1987, Dolby-SR has been available on 35mm stereo optical prints. Dolby Stereo on 70mm usually means four discrete primary channels (LCRS) with the left-center and right-center tracks dedicated to low-frequency information (below 250 Hz). The four tracks are normally use A-Type encoding, although selected 70mm films, since 1987, have utilized Dolby-SR encoding. See film soundtrack.

Dolby Surround™ : The Dolby Laboratories trademark used for surround-encoded material on non-film media, such as videocassettes, videodiscs, and television broadcasts, as well as for home surround decoding devices that do not have matrixed center-speaker output. See AC-3, Dolby Stereo, ProLogic, Dolby Motion Picture 4:2:4, SR.D, matrixing, surround-sound.

Dolby Surround EX™ : The digital release format developed by Dolby Laboratories and THX for use in "Star Wars: Episode One--The Phantom Menace." Three surround tracks are derived by matrix-encoding them in the two previously existing surround tracks. This should not be referred to as a 6.1-channel format because the additional surround channel is not a discrete channel.

Dolby tone : A reference tone, usually recorded at the head of a Dolby-A recorded tape, by which the threshold levels of the Dolby noise reduction system are adjusted for proper encoding and decoding of the companded signal.



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