28 May
2005
28 May
'05
12:15 p.m.
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