Listening Formats

When a Dolby Surround soundtrack is produced, four channels of audio information—Left, Center, Right, and Mono surround—are matrix-encoded onto two audio tracks. The stereo information is then carried on stereo sources such as videotapes and laserdiscs, from which the sourround information can be decoded by a processor to recreate the original four-channel surround sound. Without the decoder, the information plays in standard Stereo. The Dolby Surround format was updated during the 1980s and re-named Dolby Pro Logic.

Dolby Pro Logic IIIn 2000, Dolby introduced Dolby Pro Logic II (DPL II), an improved implementation of Dolby Pro Logic. DPL II processes any high quality stereo signal source into “5.1”—five separate full frequency channels (left, center, right, left surround and right surround) plus one low-frequency-effects (deep bass) channel. Dolby Pro Logic II also decodes 5.1 channels from stereo signals encoded in traditional four-channel Dolby Surround. DPL II implements greatly enhanced steering compared to DPL, and as a result, offers an exceptionally stable sound field that simulates 5.1 channel surround sound to a much more accurate degree than the original Pro Logic.

Because of the limited nature of the original DPL, many consumer electronics manufactures introduced their own processing circuitry, such as the “Jazz”, “Hall”, and “Stadium” modes found on most common home audio receivers. DPL II forgoes this type of processing and replaces it with simple servo (negative feedback) circuits used to derive five channels. In addition to five full range playback channels, Pro Logic II introduced a Music mode which would not add any processing to the left and right channels, but will still extract a centre channel and two surround channels, providing a net effect of a wider center channel.

The Pro Logic II system also features a mode designed specifically for video gaming, and it is frequently used in game titles for Sony’s PlayStation 2, Microsoft’s Xbox, Xbox 360, Nintendo’s GameCube and just recently the Wii as an alternative to digital technologies like Dolby Digital.

Digital Theatre System (DTS) is a multi-channel surround sound format used for both commercial and consumer grade applications (with slight technical differences between home and commercial variants). It is primarily used for in-movie sound both on film and on DVD. The company which created it, Digital Theater Systems, is also often referred to simply as DTS. The company is co-owned and was co-founded by film director Steven Spielberg, who felt that theatrical sound formats up until the company’s founding were no longer state of the art, and as a result were no longer optimal for use on projects where quality sound reproduction was of the utmost importance. Work on the format started in 1991, about the same time Dolby Labs was starting work on their new codec, Dolby Digital. The basic and most common version of the format is a 5.1 channel system, supporting five primary speakers and a subwoofer, referred to as an LFE (Low Frequency Effects)channel. However, other newer variants are also currently available, including versions that support up to 7 primary audio channels. DTS’s main competitors in multichannel theatrical audio are Dolby Digital and SDDS, although only Dolby Digital and DTS are used on DVDs and implemented in home theater hardware. Spielberg debuted the format with his 1993 production of Jurassic Park, which came slightly less than a full year after the debut of Dolby Digital. In addition, Jurassic Park also became the first home video release to contain DTS sound when it was released on Laserdisc in late ’93, pre-dating the first Dolby Digital home video releases which debuted in 1995.

In theatrical use, information in the form of a modified time code is optically imaged onto the film, a DTS processor in the projection booth uses this timecode to synchronize the projected image with the soundtrack audio, which is recorded in compressed form on standard CD-ROM media at 1.5 Mbit/s. The processor also acts as a transport mechanism, it holds and reads the audio discs. The units can generally hold 3 discs, allowing a single processor/transport to handle 2-disc film soundtracks along with a 3rd disc containing sound for theatrical trailers. In addition, specific elements of the imprinted timecode allow identifying data to be embedded within the code, ensuring that a certain film’s soundtrack will only run with that film.
For more info on DTS, visit their website here, or the Wikipedia entry here.
For more info on Dolby, visit their website here, or the Wikipedia entry here.

DTS variants: In addition to the standard 5.1 channel DTS Surround codec, the company has several other technologies in its product range designed to compete with similar systems from Dolby Labs. The primary new technologies are:

DTS-ES (DTS Extended Surround) – includes two variants, DTS-ES Matrix and DTS-ES Discrete 6.1, depending on how the sound was originally mastered and stored.[2] DTS-ES Discrete provides 6.1 discrete channels, with a discretely recorded (non-matrixed) center-surround channel; in home theater systems with a 7.1 configuration, the two rear-center speakers play in mono. DTS-ES Matrix provides 5.1 discrete channels with a matrixed center-surround audio channel. DTS-ES commonly works on a Matrix system, whereby processors that are compatible with the ES codec look for and recognize “flags” built into the audio coding and “un-fold” the rear-center sound from data that would otherwise be sent to rear surround speakers. This is notated as DTS-ES 5.1. Less frequently, DTS-ES data can be encoded with a Discrete 6th audio channel (the rear-center), meaning that the audio data for the 6th channel is stored separately from the other information, and is not embedded or matrixed among other channels. This is notated as DTS-ES 6.1, as the center rear is completely discrete from the other channels. ES capable processors can recognize the discrete 6th channel, and play it back if connected to the necessary speaker(s). In contrast, Dolby’s competing EX codec, which also boasts a center rear channel, can only handle matrixed data and does not support a discrete 6th channel. DTS-ES is backward compatible with standard DTS setups, so non-ES equipment which does not recognize the flags or with ES enabled equipment that lack the extra speaker connections, sound plays back in 5.1 as if it were standard DTS. Only a few DVD titles have been released with DTS-ES Discrete.

DTS NEO:6 – Neo:6, like Dolby’s Pro-Logic IIx system, can take stereo content and convert the sound into 5.1 or 6.1 channel format.

The DB System is nothing more than just another layer with speakers and amplifiers added to an existing system to enhance the sound to make it more realistic. You may know that, a 3D image of a sound can be “created” only with two speakers. Now try to imagine all this multiplied by all the numerous speakers in a DB System.

On the left and right sides of a large screen, about 10 to 12 feet apart, the DB System has 6 to 8 feet high “towers”. Each tower contains more than 10 speakers placed vertically so the sound coming out gives you the impression that it’s also coming from up and down and not just left and right. With a ‘3D Bass Field’, a special center and rear configuration of speakers, and precision amplifiers, the listener can enjoy unforgetable cinematic experience.

“When listening to music, it’s like placing separate ‘holographic images’ of the instruments of a band with distinct 3-D locations in the room.”

“From the bigscreen to a home theater, the DB System is not a new format, but an enhancement to an existing audio system, like DLP is for cinema and high definition.”

SDDS stands for Sony Dynamic Digital Sound, which is a cinema sound system developed by Sony. Digital sound information is recorded on both outer edges of the 35mm release print. 7 main channels (5 screen + 2 surround) plus a sub-bass channel are available, usually only 3 of the available 5 screen channels are used as most cinemas do not have the extra speakers installed. The digital track includes 4 fall-back tracks for occasions when the full signal is unrecoverable due to dirt or damage on the film.

For more information on SDDS, visit the website here, or the Wikipedia article here.

THX is the trade name of Lucasfilm Limited’s high-fidelity sound reproduction system for theatrical movie theaters, screening rooms, home theaters, and car audio systems. THX was developed by George Lucas’s company in 1983 to ensure that the soundtrack for the third Star Wars film, Return of the Jedi, would be accurately reproduced in the best venues.

The THX system is not a recording technology, and it does not specify a sound recording format; all digital (Dolby Digital, SDDS) and all analog sound formats (Dolby SR, Ultra-Stereo) can be “shown in THX.” THX is mainly a quality assurance system. If a producer has his or her film mixed in THX, it merely means that when the film is shown in theaters, the soundtrack will sound exactly as it did when it was mixed, provided that the theaters in question are THX-certified theaters. THX also provides certified theaters with special equipment (a special crossover) required for compliance with the standard. Theaters become certified by meeting certain acoustic and technical requirements. Some of the room requirements include a floating floor, baffled and acoustically treated walls, no parallel walls (to reduce standing waves), a perforated screen (to allow center channel continuity), and NC30 noise rated components.

According to Dr. Tom Holman, the inventor of the THX system, the name of the technology was deliberately chosen because it contained both a reference to his name, and to Lucas’s early film, THX-1138. The original name was “Tom Holman’s Crossover” (crossover sometimes referred to by the letter X, probably due to the visual similarity), but was later changed to mean “Tom Holman’s eXperiment”.

THX Ltd., the company that licenses THX and the associated technology, is based in San Rafael, California.

The distinctive crescendo used in the THX trailer is known as the “Deep Note.”

For more info on THX, visit their website here, or the Wikipedia entry here.