11 Jan
2012
11 Jan
'12
1:07 a.m.
Hi everyone,
I'm currently thinking about how to process B-format ambisonic signals.
For basic compression, gating, expanding, limiting etc things are
relatively simple: process all 4 of the W,X,Y and Z signals.
But what bout effects like Reverb: Should that effect only be applied to
the W signal? This will change the signal's direction due to the
unrelated-ness between the signals. But appling reverb to the directional
components will smear any sudden changes in location, or am I missing
something here?
I'm applying most effects in mono before doing the B-format encode, perhaps
all effects like reverb should be placed before that encoding?
Open to theory, experience, guesstimates etc :)
-Harry
11 Jan
11 Jan
2:40 a.m.
On 01/10/2012 04:07 PM, Harry van Haaren wrote:
Hi everyone,
I'm currently thinking about how to process B-format ambisonic signals.
For basic compression, gating, expanding, limiting etc things are
relatively simple: process all 4 of the W,X,Y and Z signals.
But what bout effects like Reverb: Should that effect only be applied to
the W signal? This will change the signal's direction due to the
unrelated-ness between the signals. But appling reverb to the
directional components will smear any sudden changes in location, or am
I missing something here?
I'm applying most effects in mono before doing the B-format encode,
perhaps all effects like reverb should be placed before that encoding?
One data point:
http://freeverb3.sourceforge.net/doc/AmbiSym09-JosephAndersonSeanCostello-A…
-- Fernando
12:59 p.m.
Tue, Jan 10, 2012 at 04:07:45PM -0800, Harry van Haaren wrote:
I'm currently thinking about how to process
B-format ambisonic signals.
For basic compression, gating, expanding, limiting etc things are
relatively simple: process all 4 of the W,X,Y and Z signals.
For EQ just apply the same to all components.
Dynamics are another matter. Normally the same gain change must be
applied to all channels (so you can't just replicate a mono plugin),
but driven by W only. The only exception would be transient peak
limiting: a very short gain reduction could be applied to a single
channel only. But once it lasts for more than a few tens of ms the
other channels have to follow in order to preserve the spatial image.
But in most cases such effects would be performed on the mono channels
before they are mixed into B-format.
But what bout effects like Reverb: Should that effect
only be applied to
the W signal? This will change the signal's direction due to the
unrelated-ness between the signals. But appling reverb to the directional
components will smear any sudden changes in location, or am I missing
something here?
I'm applying most effects in mono before doing the B-format encode, perhaps
all effects like reverb should be placed before that encoding?
You need a reverb that produces B format, 100% wet. It is driven by
post-fader auxiliary sends on the mono channels before they are panned
and mixed, and the output is added to the B-format master bus.
Ideally you also need to control the relative delay of the reverb send
and the input to the panner (direct sound) - it depends on distance.
You can use zita-dpl1 for B-format peak limiting, and zita-rev1 for
reverb, or use one of the AMB reverbs available for jconvolver.
I've also an AMB capable compressor but this is not yet released.
--
FA
Vor uns liegt ein weites Tal, die Sonne scheint - ein Glitzerstrahl.
1:51 p.m.
On Wed, Jan 11, 2012 at 3:59 AM, Fons Adriaensen <fons(a)linuxaudio.org>wrote;wrote:
But in most cases such effects would be performed on
the mono channels
before they are mixed into B-format.
Thanks for that.
You need a reverb that produces B format, 100% wet. It is driven by
post-fader auxiliary sends on the mono channels before
they are panned
and mixed, and the output is added to the B-format master bus.
Ideally you also need to control the relative delay of the reverb send
and the input to the panner (direct sound) - it depends on distance.
Yes, this is all easily possible, no problems.
You can use zita-dpl1 for B-format peak limiting, and
zita-rev1 for
reverb, or use one of the AMB reverbs available for jconvolver.
I've also an AMB capable compressor but this is not yet released.
While reading around I came across zita-rev1, but it seem has stereo
inputs, duplicate the mono signal to both inputs, or would you advise to
drive it with a stereo signal? I could pan the mono->stereo based on the
ambi panner control, and then send the stereo to zita-rev1, and mix in the
returned B-format?
Just loaded up zita-dpl1 -k 4, using it as an insert is no problem :)
Cheers, -Harry
2:53 p.m.
On Wed, Jan 11, 2012 at 04:51:22AM -0800, Harry van Haaren wrote:
While reading around I came across zita-rev1, but it
seem has stereo
inputs, duplicate the mono signal to both inputs, or would you advise to
drive it with a stereo signal? I could pan the mono->stereo based on the
ambi panner control, and then send the stereo to zita-rev1, and mix in the
returned B-format?
The inputs are named L and R but in -B mode you don't have to use them as
stereo. You can just use one, or both with separete aux mixes and for each
channel choose the own that works best.
The early reflections on both will be different, IIRC I tried to make the
first ones come from the left for the L input and right for the R input,
but I could as well have messed it up - it's something I need to verify
when I find the time...
Ciao,
--
FA
Vor uns liegt ein weites Tal, die Sonne scheint - ein Glitzerstrahl.
3:22 p.m.
On Wed, Jan 11, 2012 at 5:53 AM, Fons Adriaensen <fons(a)linuxaudio.org>wrote;wrote:
The inputs are named L and R but in -B mode you
don't have to use them as
stereo. You can just use one, or both with separete aux mixes and for each
channel choose the own that works best.
Cool thanks. Will report back here when I have reached a conclusion as to
what sounds best re. the mono signal.
Cheers, -Harry
PS: Fernando, thanks for the paper, really intresting although most of it
went over my head. Perhaps will revisit it if I want to make the reverb
effect in process rather than JACK insert.
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Fernando Lopez-Lezcano -
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Harry van Haaren