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[Cs-dev] Ambisonics Test File

Date2007-07-11 16:35
From"Art Hunkins"
Subject[Cs-dev] Ambisonics Test File
AttachmentsAmbisonics.csd  None  None  
Attached is a test .csd suitable for all platforms, commandline only, to
test in real time, stereo, quad and 8-channel (circular) implementations.
ASCII keys trigger different positions (in degrees) around the unit circle,
and no MIDI is required. Instructions in the form of comments are listed at
the top of the .csd.

Results/observations are as follows:

Stereo seems to be OK, at least as representing the normal frontal range
(+/- 90 degrees). (In the 90-270 degree range there is obviously something
wrong going on.)

Quad is only OK if you rearrange the speaker placement. The docs indicate
speakers placed at 90 degree intervals (clockwise) starting at 45 degrees.
One would *assume* these channels to be numbered 1-4, which is not at all
the usual numbering. At any rate, what seems to work is the following
distribution of "ambisonic channels/speakers": 1 = LF, 2 = RF, 3 = RR, 4 =
LR. Of course, this is not the usual numbering either.

Circular 8-channel is mostly a mystery to me, and does not seem to be
working in any very rational way, though whatever it is is symmetrical. 0
and 180 degrees works as a paired extension of the quad arrangement above -
with 5-8 directly behind 1-4. (In this arrangement, 0 is straight ahead and
180 degrees directly to the rear). However, this placement/interpretation
does not work at 90 and 270 degrees.

Incidentally this test can give significant data even without a monitor,
just the appropriate audio-channel interface. (Mine has 8 channels of LED's,
which gives useful visual feedback.) With this utility, the sine wave can be
set to a desired position, the tone turned on then off, csound halted, and
channel amplitudes observed.

John ff - I'd like to test with your new bformdec. Is there a way I can get
this code without having to compile Csound myself? (I don't believe I'm up
to it.) Otherwise, you can test it simply by adding a minus sign to the
first argument of the three bformdec's in the code. Personally, though, I'd
much value the opportunity to do additional testing myself.

Art Hunkins

Date2007-07-11 21:52
FromDavid Worrall
SubjectRe: [Cs-dev] Ambisonics Test File
Hi Art, All.

Why not post this test to the sursound group? There's  quite a few  
_very_ experienced people there who are used to debugging on-the-ear.
It would have the advantage that they know their systems (and there a  
quite a few varieties) and may be able to pick the problems quite  
easily.

Just a thought,


David

On 12/07/2007, at 1:35 AM, Art Hunkins wrote:

> Attached is a test .csd suitable for all platforms, commandline  
> only, to
> test in real time, stereo, quad and 8-channel (circular)  
> implementations.
> ASCII keys trigger different positions (in degrees) around the unit  
> circle,
> and no MIDI is required. Instructions in the form of comments are  
> listed at
> the top of the .csd.
>
> Results/observations are as follows:
>
> Stereo seems to be OK, at least as representing the normal frontal  
> range
> (+/- 90 degrees). (In the 90-270 degree range there is obviously  
> something
> wrong going on.)
>
> Quad is only OK if you rearrange the speaker placement. The docs  
> indicate
> speakers placed at 90 degree intervals (clockwise) starting at 45  
> degrees.
> One would *assume* these channels to be numbered 1-4, which is not  
> at all
> the usual numbering. At any rate, what seems to work is the following
> distribution of "ambisonic channels/speakers": 1 = LF, 2 = RF, 3 =  
> RR, 4 =
> LR. Of course, this is not the usual numbering either.
>
> Circular 8-channel is mostly a mystery to me, and does not seem to be
> working in any very rational way, though whatever it is is  
> symmetrical. 0
> and 180 degrees works as a paired extension of the quad arrangement  
> above -
> with 5-8 directly behind 1-4. (In this arrangement, 0 is straight  
> ahead and
> 180 degrees directly to the rear). However, this placement/ 
> interpretation
> does not work at 90 and 270 degrees.
>
> Incidentally this test can give significant data even without a  
> monitor,
> just the appropriate audio-channel interface. (Mine has 8 channels  
> of LED's,
> which gives useful visual feedback.) With this utility, the sine  
> wave can be
> set to a desired position, the tone turned on then off, csound  
> halted, and
> channel amplitudes observed.
>
> John ff - I'd like to test with your new bformdec. Is there a way I  
> can get
> this code without having to compile Csound myself? (I don't believe  
> I'm up
> to it.) Otherwise, you can test it simply by adding a minus sign to  
> the
> first argument of the three bformdec's in the code. Personally,  
> though, I'd
> much value the opportunity to do additional testing myself.
>
> Art Hunkins
> 
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_________________________________________________
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Sonic Communications Research Group,
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vip=Verbal Interactivity Project




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Date2007-07-12 15:10
FromVictor Lazzarini
Subject[Cs-dev] bformdec 8-ring
Dear all,

I just ran the bformdec using the 8-ring setup in the studio and
as I said before here it works as expected. The speaker positions
are as follows:

bformdec out                    speaker pos (degrees)
1                               22.5
2                       67.5
3                       112.5
4                       157.5
5                       202.5
6                       247.5
7                       292.5
8                       337.5

Angles are measured counterclockwise from the right,
so right -> 0, front ->90,  left ->180 and back 270.

Victor
Victor Lazzarini
Music Technology Laboratory
Music Department
National University of Ireland, Maynooth


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