There's a third method - Bruce Wiggins' Heuristic algorithm based methodology
(http://www2.derby.ac.uk/sparg-content/pdfs/bw_aes31_paper.pdf). This is, I believe, available in
his "Wigware" decoder plugins.There is also some work from China on genetic algorithm based design,
but I don't know what the current state of play is on that.
Dave
On 29/02/2012 14:28, Fons Adriaensen wrote:
On Wed, Feb 29, 2012 at 01:15:40PM +0000, Miguel Negrao wrote:
I’ve been a bit disconnected from the ambisonics world. From my past reading on
this list it is my understanding that there isn’t an explicit formula for
decoding coefficients for non-symmetrical setups. Are there currently available
tools to generate decoding coefficients for non-symmetrical setups or an
iterative algorithm that I could implement on my own ?
Two possible methods have been published.
The first is Franz Zotter's work, using an 'almost regular' virtual layout
based on
t-designs for which a decoder can be designed in closed form. Then the virtual
set
of speakers is mapped onto the real one using VBAP. As far as I know there is no
'ready to use' toolset for this method.
The second is the subject of BLaH paper #4, and is based on using a non-linear
optimisation toolset to find a solution, given the error constraints and weights
for a set of performance metrics. I developed more or less the same (even using
the same freely available non-linear library), but wasn't allowed to publish the
results, so I can confirm this can work rather well. What looks like a practical
implementation (by B,L& H) of this method is scheduled for presentation at the
next Linux Audio Conference at CCRMA.
I don't think either method can be used 'blindly', in the sense that you just
throw a set of speaker coordinates at it and get a guaranteed result. You
will have to evaluate the results, and you may have to decide on tradeoffs
and iterate the procedure using modified parameter sets. At this point you
will need some familiarity with the internals in order to be able to proceed.
Ciao,
--
These are my own views and may or may not be shared by my employer
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