[SOLVED] The multichannel audio coding standards

Surround Sound Standard

I am trying to know about the multichannel audio coding standards and til now i know 2 of them

1) MP3 Surround - BCC based (Frounhofer IIS)
2) AC3 Multichannel - (Dolby digital)

Now i want to know general idea about these coding schemes...how we are having multichanel compression with almost same datarates.

If some bust can provide me any documentation etc...that will be great.
Please put Your suggestions and whatever u think about this coding schemes....i just want to know.

It will be amazing if any one can provide some standard document say decoder description... (i know having Encoder is almost impossible)..so that can help a lot

Thanks & Regards
Chandresh

Surround Sound Standard

Dolby Digital is the marketing name for a series of lossy audio compression technologies by Dolby Laboratories.
Contents
[hide]

* 1 Versions
o 1.1 Dolby Digital
o 1.2 Dolby Digital EX
o 1.3 Dolby Digital Live
o 1.4 Dolby Digital Surround EX
o 1.5 Dolby Digital Plus
* 2 Channel configurations
* 3 Applications of Dolby Digital
* 4 Dolby Technologies in Packaged Media Formats
* 5 See also
* 6 References
* 7 External links

[edit]

Versions

Dolby Digital includes several similar technologies.
[edit]

Dolby Digital

Dolby Digital, or AC-3, is the common version containing up to 6 total channels of sound, with 5 channels for normal-range speakers (Right front, Center, Left Front, Right Rear and Left Rear) and one channel for the LFE, or subwoofer. The Dolby Digital format supports Mono and Stereo usages as well.

This codec has several aliases, which are different names for the same codec:

* Dolby Digital (promotion name, not accepted by the ATSC)
* DD (an abbreviation of above, often combined with channel count: DD 5.1)
* Dolby Surround AC-3 Digital (second promotional name, as seen on early film releases, and on home audio equipment till about 1995/6 or so)
* Dolby Stereo Digital (first promotional name, as seen on early releases, also seen on True Lies LaserDisc)
* Dolby SR-Digital (when the recording incorporates a Dolby Surround-format recording for compatibility)
* SR-D (an abbreviation of above)
* Adaptive Transform Coder 3 (relates to the bitstream format of Dolby Digital)
* AC-3 (an abbreviation of above)
* Audio Codec 3, Advanced Codec 3, Acoustic Coder 3 (These are backronyms. However, Adaptive TRansform Acoustic Coding 3, or ATRAC3, is a separate format developed by Sony)
* ATSC A/52 (name of the standard, current version is A/52 Rev. B)

[edit]

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 like the competing DTS-ES codec.
[edit]

Dolby Digital Live

Dolby Digital Live is a real-time 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.[1] The SoundStorm, used for the Xbox game console and certain nForce2-based PCs, used an early form of this technology. Dolby Digital Live is currently available in sound cards from manufacturers such as Turtle Beach[2] and Auzentech[3]
[edit]

Dolby Digital Surround EX

Whereas Dolby's Pro-Logic IIx format creates 6.1 and 7.1 channel output from stereo 2 channel (2.0), the Digital Surround EX codec adds a sixth and sometimes seventh channel to standard (non-EX) 5.1 channel Dolby Digital soundtracks.
[edit]

Dolby Digital Plus

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.
[edit]

Channel configurations

Although most commonly associated with the 5.1 channel configuration, Dolby Digital allows a number of different channel selections. The full list of available options is:

* Mono (Center only)
* 2-channel stereo (Left + Right), optionally carrying matrixed Dolby Surround
* 3-channel stereo (Left, Center, Right)
* 2-channel stereo with mono surround (Left, Right, Surround)
* 3-channel stereo with mono surround (Left, Center, Right, Surround)
* 4-channel quadrophonic (Left, Right, Left Surround, Right Surround)
* 5-channel surround (Left, Center, Right, Left Surround, Right Surround)

All of these configurations can optionally include the extra LFE channel. The last two with stereo surrounds can optionally use Dolby Digital EX matrix encoding to add an extra Rear Surround channel.

Dolby Digital decoders are equipped with downmixing functionality to distribute encoded channels to available speakers. This includes such functions as playing surround information through the front speakers if surround speakers are unavailable, and distributing the center channel to left and right if no center speaker is available. When outputting to separate equipment over a 2-channel connection, a Dolby Digital decoder can optionally encode the output using Dolby Surround to preserve surround information.

Re: Surround Sound Standard

Its gr8....information....now i am almost on track...still i am have a feeling that...most of these standars are reproduction side, means they are using them in their playback systems, before that they must be using some compression scheme (AC3 is one of them) to store this data and i am more interested in that..the core algorith in compressing 6 channel audio.
If i am not mistaking...most of these arean enhancment to that core compression algo....I think u got my point......am i right sir??

It will gr8 if we have somr about the key scheme abt thier core compression method
thanks & regards
Chandresh