Mono - Singal Channel sound Recorded through one source, replyed through one speaker.

Stereo - 2 Channel sound, replyed through front left and
right speakers.

Dolby Surround - Forerunner to Pro-Logic, three
Channels offer a pseudo surround sound.

Dolby Pro-Logic - The four channel surround sound
technology which helped kick start home cinema revolution,
Dolby Pro-Logic emerged in the mid-90's and offered a dedicated
centre channel to ensure that the movie dialogue always comes
to the centre of the screen.Comprises two stereo front speakers,
a centre channel and mono rear surrounds.

Dolby 4.0 - Four channel recording played through 4
dedicated speakers.

Dolby Digital 5.0 - Five dedicated surround channels
without a sub for bass.

Dolby Digital5.1 - Dolby Digital 5.1 can be found on most
DvDs and involves sound being digitally encoded via five
dedicated channels and a low frequency effects channel.The
speakers you need to take advantage of this are front left, front
right, rear left, rear right, centre speaker and a sub for low
frequencies.Dolby Digital improves its predecessor Dolby Pro-
Logic becasue it supports stereo rear channels and a sub
channel.

Dolby Digital EX - Enchancement to Dolby Digital 5.1 which
adds a cenre rear speaker for greater surround
relisim.Introduced in May 99 with the release of Star Wars
Episode one: The phantom Menace.

Dolby Digital Pro-Logic 2 - The Dolbys newly developedPro-
Logic 2 decoder reproduces dynamic 5.1 -channel surround from
any 2-channel source: DvDs, VHS , and television broadcasts,
radio and CD's.Dolby Pro- Logic 2 uses matrix decoding
technology thta has dramatically improved over Pro-Logic.With
Pro- Logic 2 for, instance, the surround (rear channels) are in
stereo (only mono with Pro - Logic) and playback covers the full
frequency range (only up to 7 kHz with Pro - Logic).These
improvementslet you enjoy a wide variety of 2 channel sources
with the exiciting effects of 5.1 channel surround.

DTS - Name given to a proprietary surround sound
technology developed by US frim Digital Theatre Systems, and a
direct rival to Dolby Digital.When it coems to5.1 surround, theres
not that much difference between the two technologies,
although since DTS compresses the audio less, many purists
claim it offers greater audio fidelity and richer and clearer trebles
(thats why DTS uses a tinkling piano in its promotional video
clip).Many major new movie release on DvDs come with DTS
soundtracks, though there still the exception rather than the rule
in the uk.

DTS-ES - The 6.1 channel version of DTS, which includes
the all new rear centre channel.Includes the DTS-ES matrix 6.1
surround decoding format and DTS Neo6, which allows you to
have multi channel playback from the conventional stereo source
material.Only supported by top end DvD players and Amps at the
moment.

Nicam - The format in which our terestrial TV audio is
broadcast in NICAM (digital stereo).It stands for the baffling Near
Instantaneous Compouned Audio Multiplex. Nicam VCRs offer
digital sterio sound, and the success of DvD means they can now
be bought for under £100.Nicam TVs offer stereo sound for TV
broadcast and DvD movies, but this is no replacement for 5.1
surround sound speaker system.

PCM - uncompressed stereo format offering the highest quality sound reproduction that the basic DVD format is capable of, though only two channels makes it less popular with surround sound buffs. Most commonly found on music DVDs, though some distributors have used it for feature films, most notably Criterion (The Magic Flute, Do The Right Thing) and Image (the now-deleted Paramount Marx Brothers films).

MPEG - alternative 5.1 sound format championed by the French and featured on some early French DVDs (Nikita, Le Dernier Combat, etc.) Said to be better than Dolby Digital - though I was unable to do a direct comparison, the format certainly sounds impressive enough - but now virtually obsolete as a consumer format.

DVD-Audio - relatively new 5.1 sound format that makes up the centrepiece of the DVD-Audio specification (as opposed to DVD-Video). DVD-Audio uses a lossless compression system and can potentially feature an unprecedentedly huge dynamic range (right up to 192kHz, though I've yet to come across a disc going up to more than 96). The results, if played through a system that can specifically decode DVD-Audio signals, are truly staggering - all the sonic advantages of PCM plus the six channels of Dolby Digital or DTS - but it's essentially an audio-only format. A few DVD-Audio discs offer brief video clips, but I've yet to come across one offering combined video and DVD-Audio.

Duplicated Mono - Mono sound track duplicated on left and right speakers. Rather than just centre speaker if normal mono.

DTS-ES Discrete - 6.1 channels with 6 discrete channels (left,center,right,rear left,rear centre,rear right)+ sub.

DTS-ES Matrixed - 6.1 channels with 5 discrete channels(left,center,right,rear left,rear right) + 1 matrixed channel (rear centre, this is matrixed in the left and right rear channels a bit like how pro logic is matrixed) + sub.


Dolby 4.0 - can be 2 sub-formats:
Quad Surround - 4 discrete channels: left, right, rear left, rear right.
Discrete Surround - basically a discrete version of dolby surround, unlike dolby surround all channels have full frequency range. speakers: left, centre, right, mono rear.

SDDS

SDDS is a common logo displayed on movie theater listings and
is similar to Dolby Digital and DTS. This review seeks to explain,
in simple terms, what that funny logo really means.



SDDS, or Sony Dynamic Digital Sound, is the preferred format
for filmmakers and exhibitors (www.sdds.com) Many attest to its
superiority over DTS and Dolby Digital (DD) due to its increase in
the number of speakers.

Where Can I Get SDDS?

Currently, SDDS is not available for the mainstream home
theater market. Sony choose to implement this format strictly in
theaters so they could steer clear of the fierce competition in
home theater format seen between DD and DTS. This choice also
allowed them to differentiate the home theater market from the
movie theater market.


SDDS 8 Discrete Channels

Specifically, SDDS differs from DD and DTS with the number of
discrete channels of sound. A single discrete channel of sound
recording is the sound message for one specific speaker. For
example, a normal compact disc has two discrete channels of
sound—the left and the right. One message goes to the left
speaker and the other message goes to the right speaker, thus
we have stereo. A dictation tape has one discrete channel
known as monaural. DTS and DD have 6 discrete channels, and
SDDS has 8. Where DD and DTS have 3 speaker/channels in the
front, 2 in the read/surround, and a single bass unit, SDDS has 5
in the front, 2 in the back, and 1 bass unit. These two additional
speakers in the front aim to produce an even and gap free
sound field. The five speakers are located as follows: far left,
middle left, middle, middle right, far right.


Imagine if, in a movie, one person is speaking on the left side of
the screen to another person on the right side of the screen. In
DD, a sound engineer (is that the right term?) would use the left
and middle speaker for the left person’s voice and the right and
middle speaker for the right person’s voice. With SDDS, a
sound engineer has the option of the middle left and the middle
right. This not only prevents the messy sound of two speakers
being forced to blend the same output, but also allows for a
clearer sound projection from a distinct location.

More Benefits of SDDS

Another benefit of SDDS according to Chris Carpenter, (academy
award nominated re-recording mixer, whose credits include
Independence Day, Broken Arrow, Immortal Beloved) is that the
8 channels improves the opportunities for sound effects,
because we can now place elements in different speakers and
not pile everything up, coming out of one horn.” In simple
terms, he explains that everything sounds clearer when the
sounds are separated. Having a mouse-squeak come from one
speaker, a cat-meow come from another speaker, and
soundtrack come from a third speaker allows the viewer to
mentally place the object locations with sound and to sort out
the different sound locations with their brain like evolution has
intended. It also prevents one speaker from producing many
noises which often times lead to lack of clarity.


In real simple terms, SDDS is more speakers. Therefore, it
generally sounds better.