Sounds which are below the audibility threshold for the human ear should not waste bits which could be devoted to a higher fidelity reproduction of an important sound. Perceptual encoding refers to systems which dynamically determine the number of bits of data given to a given channel of audio information based on judgements of its importance to the sound perceived by the listener. Ranada, David, "Inside Dolby Digital", Stereo Review 61, Oct 96 p81-84. The system provides a slight delay in the center channel sound to achieve a more realistic experience of the sounds arriving at the listeners location from the other speakers. Use is made of perceptual encoding to decide which parts of the audio signal would not be heard and therefore can be eliminated. The HDTV and laserdisc version of Dolby Surround AC-3 Digital runs at 384 kilobits per second and dynamically allocates the bits to the channel with the most demanding signal. It's hard to tell which is changing faster: the technology or the terminology.ĭolby Stereo Digital uses a digital data stream running at 320 kilobits per second. The AC-3 based systems are now often referred to as just "Dolby digital" in the consumer market. At the heart of Dolby Stereo Digital is and encoding scheme called AC-3.
Dolby digital surround sound movie#
Digital surround sound has been introduced into movie theaters in a form called Dolby Stereo Digital.
Dolby digital surround sound pro#
Dolby Pro Logicĭigital surround refers to surround sound systems which employ discrete digital recordings of five channels of sound information. Riggs, Michael, Digital Surround Comes Home, Stereo Review, May 1995 p 62
The center channel is recorded identically on the left and right channels. The two channels are decoded into L, R, Center and Surround upon playback. It employed a matrix encoding scheme called Dolby Surround which recorded four channels of information on two channels. Dolby Surround Sound Dolby Signal Processingĭolby Stereo is the name given to the four-channel surround sound developed by Dolby Laboratories and introduced into movie theaters in the 70's.