|Dolby Surround, an early version of surround sound, is
an analog encoding scheme used mostly for VHS movies and TV shows. It combines four
channels into stereo soundtracks. With no decoder--say, on a TV--youll hear stereo.
With a Dolby Pro Logic decoder, youll hear four channels: left, right, center, and one limited-range surround channel. A newer version, Pro Logic II, has the same left, right, and center channels, but also has two discrete, full-range surround channels for a total of five channels. Most new receivers can decode Pro Logic II; older models may do only the original Pro Logic. Youll need four or five speakers for optimal sound.
|The next step up is Dolby Digital, a digital encoding scheme thats also called Dolby Digital 5.1. Like Pro Logic II, it has full-range left and right channels in front and rear plus a center channel; it adds a subwoofer channel for deep bass (called ".1" because its limited to low-frequency effects). Dolby Digital is used on digital media such as DVDs, digital cable, digital broadcast TV, and satellite transmissions. It can also decode material that uses Dolby Surround. Virtually all new receivers and some DVD players have Dolby Digital decoders. Youll need five full-range speakers and a subwoofer for optimal sound.|
|DTS (Digital Theater Systems) is a rival to Dolby Digital, also with six channels. Its offered on most new receivers and on some DVD players. It calls for the same speaker setup as Dolby Digital.|
|Dolby Digital EX and DTS-ES are "extended surround" formats that add either a center-rear surround channel or an extra pair of rear-surround speakers that go behind the listener. With Dolby Digital EX, the two flavors are referred to, respectively, as Dolby Digital 6.1 (with three surround speakers) and 7.1 (with four surround speakers). Both formats are still relatively new and not widely used on either equipment or programming. At this stage, they are mostly for video enthusiasts. Youll need seven or eight speakers for the full effect.|
|Dolby Digital Plus is considered as the next-generation audio format that delivers
'better-than-DVD' sound in high-definition packaged media because it requires less
compression and provides up to 7.1 channels of audio.
Dolby Digital Plus provide more than just a higher bit rate and increased number of full range audio channels; it also provides new coding efficiencies for future broadcasting and streaming of multi-channel audio. It is designed to complement all high-definition programming and media. Built on Dolby Digital, Dolby Digital Plus is fully compatible with all current A/V receivers.
delivers true high-definition sound, while providing up to 7.1 channels of lossless audio
that is bit-for-bit identical to the studio master.
This Dolby sound format has been developed for high-definition disc-based media such as HD DVD and Blu-ray Disc players, to deliver audio that matches the stunning high definition pictures created by these devices.
Dolby TrueHD has been selected as a mandatory format for HD DVD and as an optional format for Blu-ray Disc.
It is also fully backward compatible with A/V receivers and HTIB (home-theaters-in-a-box) solutions supporting multi-channel Dolby Digital surround sound.
|DTS-HD High Resolution
Audio can deliver up to 7.1 channels of sound that is virtually
indistinguishable from the original soundtrack.
DTS-HD High Resolution Audio provides audio at high constant bit rates superior to standard DVDs to produce outstanding quality - reaching up to 6.0Mbps on Blu-ray discs and 3.0Mbs on HD-DVD.
It can carry up to 8 channels at 96kHz sampling frequency / 24-bit depth resolution, thereby providing high definition surround audio on content where disc space may not allow for DTS-HD Master Audio or Dolby TrueHD formats.
Like its high definition Master Audio, DTS-HD High Resolution Audio bit stream also contains the DTS 1.5 Mbps core for compatibility with existing DTS-enabled home theater systems, and delivery of 5.1 channels of sound at twice the resolution found on most standard DVDs - thus representing an instant upgrade in sound quality.
Support for DTS-HD High Resolution Audio is optional in both HD DVD and Blu-ray formats.
|DTS-HD Master Audio
delivers true high-definition sound that is bit-for-bit identical to the studio master,
while providing more than eight channels of lossless 96kHz/24-bit audio.
DTS-HD Master Audio delivers audio at super high 'variable' bit rates - reaching up to 24.5Mbps on Blu-ray discs and 18.0Mbps on HD-DVD, and constant bit rates starting at 1.5Mbps. These super high bit rates contrast heavily with the maximum of 768kbps supported on standard DVD-video for DTS Digital Surround.
Previously known as DTS++ and DTS-HD, DTS-HD Master Audio supports a virtually unlimited number of surround sound channels though DVD-HD and Blu-ray limit the number of audio channels to eight. Maximum sampling frequency supported by this format is 192kHz at a sampling depth of 24-bits. Further more, it can also down-mix to 5.1- and two-channel for compatibility with existing standard DTS-enabled AV receivers, and can deliver audio quality at bit rates extending from DTS 1.5Mbps core - up to maximum lossless bit rates supported by this format.
The also means that connecting a DTS-HD Master Audio bit stream with standard DTS-enabled AV receivers, would represent an instant upgrade in quality since DTS Digital Surround will be delivered at twice the resolution found on standard DTS-encoded DVDs.
DTS-HD Master Audio has been selected as an optional surround sound format for both Blu-ray and HD-DVD.
|A PCM track is an exact replication of the studio master,
encoded on disc without compression. The benefit to this is that it maintains the purity
of the source without any loss of fidelity that may come from compression. The downside is
that an uncompressed audio track takes up a tremendous amount of disc space, which may
(especially on single-layer BD25 discs) negatively affect the video quality of the movie.
While the Blu-ray format is capable of utilizing PCM audio up to 24-bit resolution,
studios may choose to encode at 16-bit resolution instead, depending on the bit depth of
the original source or concerns about conserving bandwidth (downsampling a 24-bit master
to 16 bits is technically not the same thing as compression).
Level of support: All Blu-ray disc players are required to support PCM audio.
|Mono||only one channel sound
active speaker: center
|Stereo||2 separate channels
active speakers: left and right front
(a Dolby prologic II decoder can simulated a 5.1 surround sound)
|Surround||3 separate channels and a coded channel
the surround channel is encoded into the stereo signal
active speakers: front left, center, front right, surround speakers in mono (encoded)
|3.0||3 separate channels
active speakers: front left, center, front right
|4.0||4 separate channels
active speakers: front left, center, front right, surround left and right in mono
|4.1||5 separate channels
active speakers: front left, center, front right, surround left and right in mono, subbass
|5.0||5 separate channels (the subbass speaker is not used)
active speakers: front left, center, front right, surround left and right in stereo
|5.1||6 separate channels
active speakers: front left, center, front right, surround left and right in stereo, subbass
|EX||6 separate channels + 1 encoded channel
active speakers: front left, center, front right, surround left and right in stereo, subbass and surround center (encoded)
|6.1||7 separate channels
active speakers: front left, center, front right, surround left and right in stereo, subbass and a separate surround back
|7.1||8 separate channels
active speakers: front left, center, front right, surround left and right in stereo, subbass, rear right and rear left