[LAD] ambisonics UHJ encoder

alex stone compose59 at gmail.com
Tue Feb 23 18:35:42 UTC 2010

On Tue, Feb 23, 2010 at 9:18 PM,  <fons at kokkinizita.net> wrote:
> On Tue, Feb 23, 2010 at 04:37:53PM +0300, alex stone wrote:
>> Jorn, Fons, i'm looking for a ladspa UHJ encoder, and can't seem to
>> find one. Any idea if such a beast exists? Or if there's a standalone
>> instance or ambdec preset i can use, and route in and out of?
> Jconvolver can do this, there's a config file
> in the distribution.
>> Some general questions.
>> When i use Jconvolver standalone (my preference) and test with a
>> *amb.conf, i get 1 input and 4 outputs WXYZ. Is this correct for 4
>> signals coming into 1, into the *amb.conf, or do i need to change this
>> to reflect individual WXYZ routing, from something like a MASTER
>> strip, or from an ambdec plugin in a channel strip? (i'm trying to get
>> the signal chain sorted out correctly.) i.e. 4 in, 4 out.
>> I'm using all mono ins for sound sources, and want to reflect
>> positioning in the busses, as i have multitrack 1st violins,
>> 2ndviolins, etc...
>> So my 1st violins (4 monotracks) are going into a 1stviolin buss (4
>> ins) and in the buss signal chain, i'm adding a ladspa amb mono
>> panner, which naturally gives me 4 outs, then the chain continues to
>> the MASTER and jconvolver, back into a jconv buss in the mixer with
>> the intent of finally routing that to the UHJ buss...
> This is not the recommended way to use such a reverb.
> The outputs from jconvolver should just go into the
> AMB mix bus. If you use Ardour you can connect them
> directly to the master bus, or you could use a 'bus'
> strip to have a gain control at that point.
> The input of jconvolver should normally come from
> post-fader aux sends on the same strips as where
> you insert the AMB panners - the panner and the
> aux send get the same post-fader signal.
> This way you can set the level of reverb for each
> panned source separately. The relative level of
> the reverb is also preserved when you use either
> the channel or master faders, as the reverb sits
> in between those, as a side chain of the master
> bus.
> In fact you can do this becaus a convolution
> reverb is a linear process: reverb (a) + reverb (b)
> = reverb (a + b).
> To be used like this the reverb must *not* include
> the direct sound.
> Ideally the input to the panner should also have
> a variable delay - to put a source at a larger
> distance you would then increase the send to the
> reverb and increase the delay in the direct sound
> via the panner. But this is a refinement that is
> difficult to arrange in Ardour, it requires using
> two strips for each panned source.
> If the reverb has many inputs corresponding to
> different source positions you would have as
> many aux busses, plus one extra for the 'tail'
> of the reverb which is usually a separate input
> for jconvolver.
> Ciao,
> --
> FA
> O tu, che porte, correndo si ?
> E guerra e morte !

Thanks Fons, that helps.

So in this case, i would run 2 instances of jconvolver, one for the
tail, and one for the UHJ conf?



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