Discussion:
Virtual Microphone Processors for HOA?
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len moskowitz
2017-10-11 16:43:53 UTC
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We're introducing OctoMic next week at AES (booth 315). It's a 2nd-order
ambisonic microphone.

Does anyone else have a virtual microphone processor for 2nd-order (or
higher) B-format?



Len Moskowitz (***@core-sound.com)
Core Sound LLC
www.core-sound.com
Home of TetraMic
Politis Archontis
2017-10-11 17:22:49 UTC
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Hi Len,

you can find a higher-order virtual microphone implementation in our web-audio ambisonics library, implementing higher-order cardioids, supercardioids, and hypercardioid patterns. The library is open-source and generates the patterns for any order, even though Web Audio supports up to 4th-order signals (without tricks) at that point. You can find a real-time 3rd-order demo here:

https://cdn.rawgit.com/polarch/JSAmbisonics/e28e15b384f2442a66fadc0035439c64ed65fa4d/examples/hoa-virtual-mic.html

If you manage to stream your 9 second-order signals somehow in the browser, then you can process them live there, but unfortunately I think HTML5 supports up to 8 channels for streaming audio, so at the moment HOA material works only with wav/ogg files.

Regards,
Archontis Politis
Post-doctoral Researcher
Department of Signal Processing and Acoustics
Aalto University
Finland


On 11 Oct 2017, at 19:43, len moskowitz <***@optonline.net<mailto:***@optonline.net>> wrote:

We're introducing OctoMic next week at AES (booth 315). It's a 2nd-order ambisonic microphone.

Does anyone else have a virtual microphone processor for 2nd-order (or higher) B-format?



Len Moskowitz (***@core-sound.com<mailto:***@core-sound.com>)
Core Sound LLC
www.core-sound.com<http://www.core-sound.com>
Home of TetraMic
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Stefan Schreiber
2017-10-11 23:50:13 UTC
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Post by Politis Archontis
Hi Len,
https://cdn.rawgit.com/polarch/JSAmbisonics/e28e15b384f2442a66fadc0035439c64ed65fa4d/examples/hoa-virtual-mic.html
If you manage to stream your 9 second-order signals somehow in the browser, then you can process them live there, but unfortunately I think HTML5 supports up to 8 channels for streaming audio, so at the moment HOA material works only with wav/ogg files.
I don't believe this is (still?) true:

https://github.com/GoogleChrome/omnitone
Post by Politis Archontis
* First-order-ambisonic stream
* High-order-ambisonic stream: 2nd and 3rd order.
The input audio stream can be either an HTMLMediaElement (<video> or
<audio> tag) or a multichannel AudioBufferSourceNode.
BR

Stefan
Post by Politis Archontis
Regards,
Archontis Politis
Post-doctoral Researcher
Department of Signal Processing and Acoustics
Aalto University
Finland
We're introducing OctoMic next week at AES (booth 315). It's a 2nd-order ambisonic microphone.
Does anyone else have a virtual microphone processor for 2nd-order (or higher) B-format?
Core Sound LLC
www.core-sound.com<http://www.core-sound.com>
Home of TetraMic
Politis Archontis
2017-10-12 05:30:32 UTC
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Hi Stefan,

On 12 Oct 2017, at 02:50, Stefan Schreiber <***@mail.telepac.pt<mailto:***@mail.telepac.pt>> wrote:

Omnitone offers ambisonic decoding and binaural rendering of:

* First-order-ambisonic stream
* High-order-ambisonic stream: 2nd and 3rd order.

The input audio stream can be either an HTMLMediaElement (<video> or <audio> tag) or a multichannel AudioBufferSourceNode.

I may be wrong, these things change quite quickly, but the HTMLMediaElement, which could be used for live streaming does not support more than 8ch at the moment, hence it would work with FOA only, while the AudioBufferSourceNode can handle up to 32 (hence 4th-order) but works only with loading audiofiles.

BR,
Archontis Politis





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s***@mail.telepac.pt
2017-10-12 09:39:54 UTC
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Post by Politis Archontis
Hi Stefan,
On 12 Oct 2017, at 02:50, Stefan Schreiber
  * First-order-ambisonic stream
  * High-order-ambisonic stream: 2nd and 3rd order.
The input audio stream can be either an HTMLMediaElement (<video>
or <audio> tag) or a multichannel AudioBufferSourceNode.
I may be wrong, these things change quite quickly, but the
HTMLMediaElement, which could be used for live streaming does not
support more than 8ch at the moment, hence it would work with FOA
only, while the AudioBufferSourceNode can handle up to 32 (hence
4th-order) but works only with loading audiofiles.
You are probably quite right on all...

Best regards

Stefan 
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Dave Malham
2017-10-12 14:06:37 UTC
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Why on earth do people hard code these channel limits in? Ok, I understand
the general thinking is based on performance considerations but...Moore's
Law is not a new thing and whatever you think are the limitations today are
not what they will be next year. I thought we had gotten past low channel
counts when Reaper came out.

Dave
Post by Politis Archontis
Hi Stefan,
Post by Politis Archontis
* First-order-ambisonic stream
* High-order-ambisonic stream: 2nd and 3rd order.
The input audio stream can be either an HTMLMediaElement (<video> or
<audio> tag) or a multichannel AudioBufferSourceNode.
I may be wrong, these things change quite quickly, but the
HTMLMediaElement, which could be used for live streaming does not support
more than 8ch at the moment, hence it would work with FOA only, while the
AudioBufferSourceNode can handle up to 32 (hence 4th-order) but works only
with loading audiofiles.
You are probably quite right on all...
Best regards
Stefan
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--
As of 1st October 2012, I have retired from the University.

These are my own views and may or may not be shared by the University

Dave Malham
Honorary Fellow, Department of Music
The University of York
York YO10 5DD
UK

'Ambisonics - Component Imaging for Audio'
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Sven König
2017-10-11 18:56:10 UTC
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Post by len moskowitz
We're introducing OctoMic next week at AES (booth 315). It's a
2nd-order ambisonic microphone.
wow that's sounds interesting!
could something like the harpex method theoretically be used to upmix
2nd-order to 3rd-order yielding better results than upmixing b-format?

sven.
s***@mail.telepac.pt
2017-10-11 20:54:51 UTC
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Post by Sven König
Post by len moskowitz
We're introducing OctoMic next week at AES (booth 315). It's a
2nd-order ambisonic microphone.
wow that's sounds interesting!
could something like the harpex method theoretically be used to
upmix 2nd-order to 3rd-order yielding better results than upmixing
b-format?
sven.
Harpex works only at 1st order. It is not likely that the Harpex
method can be extended to >= 2nd order, for mathematical reasons.

Best,

Stefan
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