f...@kokkinizita.net wrote:
On Sat, Jan 22, 2011 at 04:38:19PM +0000, Augustine Leudar wrote:
Im sure Im missing something obvious here but humour me. With a stereo
signal I can just place two speakers in a line and have my stereo signal
send two discrete channels to each speakers, each channel representiong one
channel of my stereo microphone. The same with quadrophonic (with no
matrixing nonsense) - four mics go to four speakers placed in a square -
works fine, tried it hundreds of times, no decfoding involved. Why cant you
do the same for 3 dimensianal sounds ? Four mics surround sending discrete
channels to four spekers placed in a square and one for height information
going to a mic above your head - this should naturally represent the sound
field without any decoding , Ive done this and it has been quite effective
- so why the need for elaborate and expensive decoding ?
Your question reveals that you have not even started to study and
understand Ambisonics theory - the answer would be quite evident
in the other case. You could as well ask a engineer why he needs
complex numbers while you can do your bookkeeping without.
Hoping you will eventually have a go at it, I'll provide a
provisional answer. There are several good reasons why AMB
uses 'encoded' signals:
* It makes the recorded/transmitted content independent of the
technology used to produce it and of the speaker setup used
to reproduce it. It provides a 'natural' representation that
will always work and capture the essential information.
* The encoded form makes it easy to apply some transformations
on the signal wich would otherwise be quite difficult to
perform, e.g. rotation.
* The encoded form is required anyway for correct reproduction
as this requires some processing wich has to be performed on
signals exactly this format, and and can't be done on speaker
signals (unless you encode them, operate on them, and decode
them again).
* A 1:1 mic to speaker mapping may work in simple cases, but it
does not scale to the equivalent of higher order AMB. First
order AMB was the start of the art 30 years ago, today we can
do much more, just because we are using an encoded format.
I respectfully disagree a second time. IMO the question was pretty good,
and required a thought answer.
In fact, the introduced "system" might deliver better results than say
Dolby Pro Logic IIz.
Gives to think, for some reason...
Best,
Stefan
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