[LAU] ambisonics: fons ambdec and muse.demon.co.uk ambidec

[Jörn Nettingsmeier]

hi olaf!


On 01/06/2011 11:14 PM, sh0099 at gmx.de wrote:
> Hallo
>
> I was wandering if i can use
> "First and Second Order Ambisonic Decoding Equations"
> from this page:
> http://www.muse.demon.co.uk/ref/speakers.html
>
> for setups in ambdec by fons?
> http://www.kokkinizita.net/linuxaudio/
>
>
> The Speaker Setups are from/for a programm called "Ambisonics
> Command-Line Decoder"
> http://www.muse.demon.co.uk/utils/ambidec.html
>
> my problem is that the speaker position is of demons ambidec is in
> positions in the room (x,y,z) and not as dist,azim,elev as in fons ambdec
>
> is there some handy script somewhere to convert between these two?

why would you want to do that? ambdec comes with a number of example 
configurations, and iirc, they cover all the speaker layouts that are 
covered on richard's page, plus a few more.
or do you want to create a custom layout and have amb*i*dec compute a 
configuration for you?

if so, conversion between polar and cartesian is not too hard... if your 
listening position is at the origin of both coordinate systems, then 
(off the top of my head), you should get something like:

azimuth = arctan (y/x)
elevation = arctan (z/(sqrt(x^2 + y^2))
r = sqrt (x^2 + y^2 + z^2)

(do double-check that, it's late and i don't even have a scrap of paper 
here to draw it up properly...)

i'm pretty sure that the custom layout matrix you will get out of 
amb*i*dec will yield worse results than ambdec, because it does not do 
proper dual-band decoding.

out of curiosity, what layout are you looking for?


best,

jörn