[PD] HOA / spatialization approaches for a hemisphere

[Pierre Guillot]

My VBAP repository is for "personal" use, I'm not sure that I will ever
publish an "official" release but everything should work ! I did this
because there were bugs in the "official" implementation when using a very
large number of loudspeakers and I couldn't solve the problem from the
original code (I couldn't find the problem in fact...). If you want to be
sure to have something durable I suggest you to use the abstraction p.vbap
but the compiled externals are much more efficient. One last thing: there
is no "spread" factor (MDBAP)  but you can do it manually in Pd. The
principles are explained in the paper Uniform Spreading Of Amplitude Panned
Virtual Sources (
https://aaltodoc.aalto.fi/bitstream/handle/123456789/2345/article4.pdf) and
the implementation is explained in Generic panning tools for MAX/MSP (
http://cnmat.org/ICMC2000/pdf/VBAP.pdf
<(http://cnmat.org/ICMC2000/pdf/VBAP.pdf>).
Cheers

2017-06-25 0:09 GMT+02:00 <jmejia at anestheticaudio.com>:

> Thanks Pierre! That's all great advice. I'm gonna dig into VBAP - it's
> been awhile since I've messed with that. Maybe that will work better.
>
> I'll give your building repo a shot https://github.com/pierreguillot/vbap
>
> (unless you have OSX binaries?)
>
> but I also wonder about all these others:
>
> https://puredata.info/downloads/vbap/releases
>
> vbap-v0 on dekken
>
> https://sourceforge.net/projects/pure-data/files/libraries/vbap/
>
> Thanks!
>
> -Jesse
>
>
>
>
> On 2017-06-24 03:26, Pierre Guillot wrote:
>
> Hi Jesse,
>
> With Ambisonics, ideally your loudspeakers should discretize perfectly a
> sphere, you should have your head at the exact center of this sphere, etc.
> and perhaps if you forget that your head interferes and the loudspeakers
> don't generate plane waves you'll be able to reconstruct a coherent sound
> field... But to avoid these restrictions (because very few people have a
> full sphere of loudspeakers - or want to ask the audience to be completely
> crushed at the center of the sphere) there are several techniques :
> optimizations of the energy and/or velocity vectors, optimizations of the
> decoding, etc. The problem is that none of the solutions are completely
> generic. Your choice must be driven by your approach and your goal.The
> advantage of Ambisonics lies in its intermediary representation of the
> sound field that allows to apply transformations (rotation or whatever) and
> to decode for different loudspeakers configurations. But if you just want
> to spatialize individuals point sources, you can also use VBAP that is
> perhaps much more accessible. Nevertheless yes, you can surely find a way
> to decode the sound field for two ring of loudspeakers with Ambisonics (we
> can discuss it if you want). And one good rule is just to avoid placing
> sources where the loudspeakers are missing. I don't know if I really answer
> the question, I hope a bit :)
>
> Cheers,
>
> Pierre
>
>> Date: Fri, 23 Jun 2017 16:19:29 -0600
>> From: jmejia at anestheticaudio.com
>> To: pd-list at lists.iem.at
>> Subject: [PD] HOA / spatialization approaches for a hemisphere
>> Message-ID: <3149263781acf8439b762eef943d60e5 at anestheticaudio.com>
>> Content-Type: text/plain; charset="utf-8"
>>
>> Hi List,
>>
>> I'm putting together a 32 channel HDLA and looking for spatialization
>> advice. The configuration will be two rings, one higher than the other,
>> and I've been thinking a bit smaller/closer to approximate a hemisphere.
>> But that's flexible - they could be parallel rings if it simplifies
>> things.
>>
>> I have some (limited) experience using HoaLibrary + PD for 2D ambisonics
>> - so my initial thought was to try the 3d externals there - however I'm
>> not sure if it actually makes sense to build an abstraction setup for a
>> sphere of twice as many channels while limiting access to the upper
>> hemisphere only. I'm assuming there would be some problems with that
>> approach.
>>
>> I found a few papers on mixed-order ambisonics - by Chris Travis and
>> also the AmbiX crew - but I'm not sure if there's away to implement that
>> stuff with HoaLibrary. I'm also open to using different software if
>> something else is recommended instead.
>>
>> Thanks for any advice!
>>
>> -Jesse
>
>
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