Re: Sound differences
- From: nospam@xxxxxxxxxx (Paul)
- Date: Sat, 03 Jun 2006 01:09:21 GMT
In article <6D4gg.1002637$xm3.388649@attbi_s21>, "Travis King"
<Anonymous@xxxxxxxx> wrote:
What's the difference between 6-channel direct, optical, and coax? Those
are my options on my Logitech Z-680's. I'm using a Creative Audigy 24-bit
(5.1) soundcard on my Asus K8N. Thanks.
Well, let's consider the works from end to end.
First we need some audio source material. Three sources I can
think of, are DVD movies, games, and say any other wave audio
source.
The DVD movie is recorded in some form of Dolby Digital. That
means there is a 5.1 sound track on there. So that is one reason
to have the 6 channel config on your Logitech speakers.
A second scenario might be a game. Some games have "surround"
effects, so you get directional info in a first person shooter.
A third scenario might be listening to CDs, .wav files, MP3s and
the like. AFAIK, these will be stereo, unless you enable
some option to synthesis a multi-speaker environment.
Now we get to the output side of the Audigy. Basically, in the
options you named above, we have analog 5.1 and some form of SPDIF.
SPDIF consists of two channels. To stuff six channels of information
into a two channel carriage, requires compression/coding. One
standard is Dolby Digital AC-3. For the encoding process, you
need a license, and not all sound devices come with a license
and the necessary code, to convert analog 5.1 information, into
an AC-3 stream.
When you play a DVD, this problem has a simple solution. The
sound on the DVD, already is encoded in AC-3. All the DVD player
software has to do, is send the stream to your SPDIF (optical or
coax) interface, without interaction.
In the case of a game, the game is not likely to have a license.
Maybe there are other encoding standards, but then your Logitech
speakers would probably not understand.
So the crux of the matter, is whether the Audigy has a license
for Dolby Digital AC-3 encoding. If it does, then your optica/coax
option is sorta equal to the direct (analog) six channel interface.
Now, all is not rosy, because even if you happen to have a software
encoder to drive the SPDIF output, there can be a delay of 0.5 to
1 second, before the sound is output. In some cases, there can be
lip sync problems introduced by attempting to go digital.
On my A7N8X-E Deluxe motherboard, there is a DSP logic block in
the Southbridge, that can do Dolby Digital. Apparently the latency
is quite low through there, certainly lower than your average
Dolby software encoder.
In summary, if you use the direct (analog) interface method,
you are likely to have a "seamless" experience. Whatever audio
effects exist on the source side, are likely to come out of the
speakers. If you go the digital route, then what happens will depend
on the licensing issue, and exactly what features your Audigy has
got. If a pure software encoder was used, then expect an extra
delay in the sound leaving the speakers. Good applications would be
aware of this encoding process, but there are situations where you
simply cannot delay other information streams, to resync the sound
(like a gaming situation).
Get out your library card - here are some references to correct
any mistakes I made :-)
http://en.wikipedia.org/wiki/AC-3
http://en.wikipedia.org/wiki/S/PDIF
http://en.wikipedia.org/wiki/Environmental_audio_extensions
"Modern Audio Technologies in Games"
http://www.digit-life.com/articles2/sound-technology/index.html
HTH,
Paul
.
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