[openal] Speaker test

Anders Genell anders.genell at gmail.com
Mon Jun 5 13:34:05 EDT 2017

> 5 juni 2017 kl. 17:36 skrev Chris Robinson <chris.kcat at gmail.com>:
>> On 06/04/2017 09:43 PM, Anders Genell wrote:
>> Oh?! Fantastic! Is it documented somewhere how to implement this?
>> Looking at e.g. Fons Adriaensen's ambisonics decoder for linux, it
>> seems angles should be possible too.
>> http://kokkinizita.linuxaudio.org/linuxaudio/adec-pict.html
> What exactly do you mean by angular correction? The speaker itself being turned to a different angle (e.g. it facing away from you instead of toward you), or that it's placed at a different angle relative to your front (e.g. front-right is 40 degrees to your right, instead 30 degrees)? The latter is possible by generating new decoder matrices for your specific layout, using something like the Ambisonic Decoder Toolbox (a set of MATLAB/GNU Octave scripts to generate ambisonic decoders). OpenAL Soft doesn't currently have a way to generate the decoders itself, since the math behind doing so isn't very straight forward, but I do plan on doing it eventually.
> For setting the time/phase correction, the first step would be to look at the ambdec presets provided in the presets/ directory and find the one that's most appropriate for your speaker setup (keeping in mind that 7.1 should use "hexagon"). Make a copy of that file and edit it. In the "speakers" section of the file, you'll see speaker IDs and their distances. Set the the correct distances (in meters) for each speaker and save. Then run alsoft-config, and under the Renderer tab you'll see the Decoder Configuration section; click Browse and select the new preset you made for the correct speaker layout, and click Apply. It's now set. You can also enable High Quality Mode while you're there if you wish to use frequency-dependent processing.
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Oh, that is just amazing!!
I had no idea this level of control was possible!
I'll dig into this with uncurbed enthusiasm. 

And, yes, angular correction in that they are placed at different angles relative to my front. 

Thanks a million!

If I ever happen to be in the same location as you or some of the Csound developers (Victor Lazzarini, Rory Walsh, John Ffitch and a few others mainly) the volume of beer I would need to buy to settle my debt would have its own moon. 


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