On 2/26/21 7:26 AM, Brandon Hale wrote:
...
I'm not really looking for environments for making compositions. I'm
mostly looking for that decoder that can decode to arbitrary and weird
speaker arrays on Linux.
Hi Brandon,
You will need two things:
- a way to design a decoder
- a way to run that decoder
For designing Ambisonics decoders I use ADT (the Ambisonics Decoder
Toolkit, by Aaron Heller):
https://bitbucket.org/ambidecodertoolbox/adt/src/master/
You will probably want to read through the references there to learn
about the different design methods available, the respective tradeoffs
and tricks. It is not extremely difficult but like everything else you
have to learn stuff.
This is definitely not a "single button, press here for decoder" solution.
ADT will generate a proper Ambisonics decoder, dual band with phase
matched filters, near field compensation filters for the speakers and
(optional) level and delay compensation for your array. It can output
ambdec configuration files (but limited to 3rd order, of course) and
also Faust source code for the full decoder (which is what I currently
use). Faust can be compiled to any number of plugin and whatnot formats.
I have used standalone QT/Jack apps in linux and supercollider plugins -
I think it can easily generate pd as well.
For very irregular arrays and "weird speaker locations" there is, sorry,
no magic. In some cases you might conclude that Ambisonics is not the
correct solution (for very irregular arrays).
I have successfully used ADT to create decoders for our concert systems
(up to 32.8) and for our Stage small concert hall with a 56.8 system and
Listening Room (full 3D 22.8). A LOT of work to get properly calibrated
arrays but the result sounds pretty darn good (if I may say).
My experience with fairly regular "dome" speaker arrays is that ALLRAD
works best (Slepian decoders have the appeal of using the "right"
harmonic functions but in my experience they are not good with highly
irregular arrays).
If your speaker coverage has "holes" then it is all about tradeoffs. You
can optimize for even energy (loudness) but then you will have
directional errors and/or mismatches of perceptual cues at low and high
frequencies, if you minimize directional errors you will have uneven
loudness. If you want Ambisonics you need decent speaker coverage for
best results.
You can look at the plots of meaningful parameters when designing your
decoder with ADT and see what you get for different configurations.
This is all with the caveat that there are limits to your perception, so
what looks like an error on paper might not be significant in practical
listening conditions, and as Fons rightly points out, going above order
7 does not make much sense.
Some data from a composer's point of view here (Natasha Barrett):
https://www.natashabarrett.org/Barrett_IRCAM_Report_v2.pdf
In the paper she explores the limits of what was for her significant in
terms of max ambisonics orders. My current compositional work uses mixed
5th/2nd order Ambisonics and I am quite happy with the results (in a
56.8 system that can potentially decode 6th order[*]).
Hope this helps,
-- Fernando
[*] https://lac.linuxaudio.org/2019/doc/lopez.pdf
On 2/25/21 4:42 PM, Jeanette C. wrote:
Hey hey Brandon,
Feb 25 2021, Brandon Hale has written:
...
Are there any good alternatives for rendering ambisonic and wavefield
synthesis audio files?
...
It's no surprise that I willmention Csound, which can do quite a bit in
the way of ambisonics. I'm sure PD (PureData) and SuperCollider (SC) can
do the same and they have good graphical interfaces.
There are also LADSPA/LV2 plugins to produce ambisonic outputs, not sure
what exactly there is. Fons has released a few plugins.
For Wavefields synthesis I only know of SWONDER, which is older than SSR
and - I think - no longer maintained, but it's been ages since I looked
at that.
Csound, PD and SC also offer many utilities for building good
soundscapes and sound design in general. Depending on what you are
looking for in the way of textures, Luigi Verona has talked about his
way of creating melodic textures, scapes and clouds. Perhaps that would
serve your purposes?
HTH.
Best wishes,
Jeanette
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