La majoria dels DVDs tenen el so en AC3 (5.1) o en AC3 estèreo (2.0). Molt pocs DVDs (menys de l'1%) tenen el so en AC3 EX (5.1, que fa veure que es un 6.1), i també altres DVDs (també menys del 1%) tenen el so en AC3 Surround EX (que descodificant-los amb un equip preparat, et reparteix els canals a 6.1 o 7.1).
Potser he corregut massa, i Star Wars és de les pelis que entren dins de l'1%, i el castellà i l'anglès sí que potser estan gravats en AC3 EX o AC3 surround EX. Per fer-ho fàcil, normalment ho diu a la caràtula si és EX, Surround Ex, o 5.1 normal. A part, si treballéssis amb aquest audio amb un programa que es diu EAC3to, allà també diu exactament quin tipus d'àudio és.
Però el català si està en 2.0, segur que no és EX (estèreo normal i corrent).
Aquí tens més info:
Està en anglès...
Dolby Digital includes several similar technologies, which include Dolby Digital, Dolby Digital EX, Dolby Digital Live, Dolby Digital Surround EX, Dolby Digital Plus, and Dolby TrueHD.
Dolby Digital logo that is sometimes shown at the beginning of broadcasts, feature films, and gamesDolby Digital, or AC-3, is the common version containing up to six discrete channels of sound. The most elaborate mode in common usage involves five channels for normal-range speakers (20 Hz – 20,000 Hz) (right front, center, left front, right rear and left rear) and one channel (20 Hz – 120 Hz allotted audio) for the subwoofer driven low-frequency effects. Mono and stereo modes are also supported. AC-3 supports audio sample-rates up to 48 kHz. Batman Returns was the first film to use Dolby Digital technology when it premiered in theaters in Summer 1992. The Laserdisc version of Clear and Present Danger featured the first Home theater Dolby Digital mix in 1995.
This codec has several aliases, which are different names for the same codec:
Dolby Digital, DD, Dolby Surround AC-3 Digital, AC3, ATSC A/52
Dolby Digital EX
Dolby Digital EX is similar in practice to Dolby's earlier Pro-Logic format, which utilized Matrix technology to add a center and single rear surround channel to stereo soundtracks. EX adds an extension to the standard 5.1 channel Dolby Digital codec in the form of matrixed rear channels, creating 6.1 or 7.1 channel output. However, the format is not considered a true 6.1 or 7.1 channel codec because it lacks the capability to support a discrete 6th channel unlike the competing DTS-ES codec.
Dolby Digital Surround EX
The Cinema Version of "Dolby Digital EX" is called Dolby Digital Surround Ex and works the same way. Dolby Digital Surround EX was co-developed by Dolby and Lucasfilm THX. It provides an economical and backwards-compatible means for 5.1 soundtracks to carry a sixth, center back surround channel for improved localization of effects. The extra surround channel is matrix encoded onto the discrete Left Surround and Right Surround channels of the 5.1 mix, much like the front center channel on Dolby Surround encoded stereo soundtracks. The result can be played without loss of information on standard 5.1 systems, or played in 6.1 or 7.1 on systems equipped with Surround EX decoding and additional speakers. Dolby Digital Surround EX has since been used for the Star Wars prequels on the DVD versions and also the remastered original Star Wars trilogy. A number of DVDs have Dolby Digital Surround EX audio option.
Dolby Digital Live
Dolby Digital Live (DDL) is a real-time hardware encoding technology for interactive media such as video games. It converts any audio signals on a PC or game console into the 5.1-channel Dolby Digital format and transports it via a single S/PDIF cable. A similar technology known as DTS Connect is available from competitor DTS.
Dolby Digital Live is currently available in sound cards from manufacturers such as Creative Labs, TerraTec, Turtle Beach, HT OMEGA SYSTEM, Auzentech and Asus using C-Media chipsets. The SoundStorm, used for the Xbox game console and certain nForce2-based PCs, used an early form of this technology.
Dolby Digital Plus
E-AC-3, more commonly known as Dolby Digital Plus, is an enhanced coding system based on the AC-3 codec. It offers increased bitrates (up to 6.144 Mbit/s), support for more audio channels (up to 13.1), improved coding techniques to reduce compression artifacts, and backward compatibility with existing AC-3 hardware.
Dolby TrueHD, developed by Dolby Laboratories, is an advanced lossless audio codec based on Meridian Lossless Packing. Support for the codec is mandatory for HD DVD and optional for Blu-ray Disc hardware. TrueHD supports 24-bit, 96 kHz audio channels at up to 18 Mbit/s over 14 channels (HD DVD and Blu-ray Disc standards currently limit the maximum number of audio channels to eight). It also supports extensive metadata, including dialog normalization and Dynamic Range Control.[/hide]