[linux-audio-dev] Dumb question regarding CMT's ambisonic plugins

Ivica Ico Bukvic ico at fuse.net
Sat May 28 16:58:53 UTC 2005

Thank you very much!

Best wishes,

Ivica Ico Bukvic, composer & multimedia sculptor

> -----Original Message-----
> From: linux-audio-dev-bounces at music.columbia.edu [mailto:linux-audio-dev-
> bounces at music.columbia.edu] On Behalf Of fons adriaensen
> Sent: Saturday, May 28, 2005 10:18 AM
> To: A list for linux audio users; The Linux Audio Developers' Mailing List
> Subject: Re: [linux-audio-dev] Dumb question regarding CMT's ambisonic
> plugins
> Helllo Ico,
> > I have been messing with the ambisonic plugins provided in the CMT
> ladspa
> > collection. I am namely looking into a simple implementation of B-format
> > 1ch->4ch encoder. The problem is that I am failing to figure out how to
> use
> > this on a simple mono (non-encoded) sound input in order to control its
> > diffusion over 4 channels.
> I'm not sure what you mean by diffusion. For a mono source, you basically
> have two options:
> 1. Just send it to the B-format W channel, and not use X,Y,Z
>   Thechnically that's not a 'legal' B format, but what you get is that
>   the sound will come equally loud out of all speakers.
> 2. Use a B-format panner to put it into a particular direction.
>    Remember that ambisonics encodes source direction, not position,
>    i.e. it does not include any notion of distance. This is normally
>    encoded by changing the direct / reflections / reverb ratios.
> Regarding the CMT set of ambisonics plugins, I remember having tested
> some of them at least a year ago and the conclusion was they have some
> problems.
> > When running it via Ardour and sending it to 4
> > separate busses via this plugin, even though the x, y, and z coordinates
> do
> > affect the output of the 4 channels, they do not conform to the expected
> > 3,4,2,1 output (I presume these correspond to 4 speaker outputs, but I
> am
> > also having doubts about this as well, so your help in understanding
> this
> > better would be most appreciated).
> Seems like you need two things:
> 1. a B-format panner for ardour, so you can mix a number of mono inputs,
>   giving each of them a 'direction' and maybe (via additional outputs)
>   controlling their distance, and
> 2. a B-format to 4 speaker decoder following the master mixer strip.
> I have these things in house, and I'm using them all the time, but they
> are not in a state suitable for release. They will be released some time,
> and if you need them badly, I could change some priorities...
> OTOH, I remember you've been exploring SuperCollider recently, and that
> has everything you need on board. Have a look at the PanB2, PanB and
> DecodeB2 Ugens.
> --
> FA

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