Old 05-24-2021, 03:23 PM   #1
Jensus
Human being with feelings
 
Join Date: Apr 2021
Posts: 11
Default Ambisonic IR

Hi, I am trying to figure out how to create the best and easiest ambisonic impulse responses for software like ambi verb and wwise convolution.
I would like to
1. record IR for a specific place in the sphere wehere I will pan my monophonic sound source.
2. record IR to be used more freely across the whole sphere.
Should I for no. 1 place the speaker with the white noise/sine sweep at the position I want to place the virtual sound source and record it there?
For no. 2 record several IR around the location and combine them? Or fx recording it from a 2 m distance and use that for the entire sphere?
Does anyone have experience with this?
Jensus is offline   Reply With Quote
Old 05-25-2021, 09:55 AM   #2
Kewl
Human being with feelings
 
Join Date: Jan 2009
Location: Montreal, Canada
Posts: 81
Default

If a "true stereo" IR reverb is four IRs (2*2 matrix), a "true 1st order" IR reverb would be 16 IRs (4*4 matrix). It's been on my "to experiment list" for the past ten years...

https://www.avosound.com/en/tutorial...ono-and-stereo
Kewl is offline   Reply With Quote
Old 05-25-2021, 11:02 AM   #3
plush2
Human being with feelings
 
Join Date: May 2006
Location: Saskatoon, Canada
Posts: 1,999
Default

Quote:
Originally Posted by Kewl View Post
If a "true stereo" IR reverb is four IRs (2*2 matrix), a "true 1st order" IR reverb would be 16 IRs (4*4 matrix). It's been on my "to experiment list" for the past ten years...

https://www.avosound.com/en/tutorial...ono-and-stereo
Would it not simply be 16 independent IR processes for first order and not 16 different channels in the IR itself? Or wouldn't it actually be 12 since the W channel doesn't need to be convolved independently for each axis but rather as a matrix of the x/y/z signals? A stereo impulse is still only 2 channels, the true stereo part is to convolve the left channel and right channel independently through that stereo impulse. This is then mixed from the the now 4 channel result back down to stereo. I was just thinking, when I take an impulse with my first order mic I don't need to do it 4 times from 4 locations to get a true ambisonic IR. Perhaps that's what you meant all along though? I'm just trying to get it straight in my mind.

Anyways, for number 1 you do want to place the speaker at the location you want the emitter at and the mic in the spot you want the listener to be located. In my understanding, if you move that emitter around the listener it will be like rotating the entire room as you can't virtually move that speaker after the fact.

However...Zylia just did a very interesting demo of synthesizing multiple ambisonic recording positions in a room. I assume the same idea could be used to synthesize multiple ambisonic IRs, especially since they used wwise and unity to do it. That is my answer to question 2.

It is labor and processor intensive so make sure it's going to pay off in the end.
__________________
mymusic - http://music.darylpierce.com
mywork - http://production.darylpierce.com
mypodcast - Ultimate Sound Test
plush2 is offline   Reply With Quote
Old 05-27-2021, 03:03 AM   #4
Jensus
Human being with feelings
 
Join Date: Apr 2021
Posts: 11
Default

My main goal is to do a 360 video and audio recording and then ad sound sources with a reverb that is coherent with the space.
Knowing that I can make an ambisonic IR of the speaker placed at the right position of the panned mono source, must be my primary focus after getting into the complexity of this problem.
Ambi Verb and Wwise Convolution lets you import a 4 channel ambisonic IR recording. Regarding panning a sound source in the entire sphere it seems to be the course of action to use one IR and trust that the localization information from the direct sound source will overshadow the mismatch with the spatial reverb.
AudioEase is offering a set of ambisonic reverbs in their 360 pan suite, but I just thought it would be great to enhance the realism with the correct reverb information.
I have also heard of examples where you can re-render the IR using a decoder plugin and then do a soundfield rotation and process the next mono sound source at the new position. And that some are blurring the localization of the direct sound if it clashes with the reverb.
Is it possible at all to create a 16 channel IR file and use it with a 360 panner in any software today?

Last edited by Jensus; 05-27-2021 at 06:25 AM.
Jensus is offline   Reply With Quote
Old 05-27-2021, 05:16 AM   #5
jm duchenne
Human being with feelings
 
jm duchenne's Avatar
 
Join Date: Feb 2006
Location: France
Posts: 827
Default

How to create the 16 channels IR file I don't know, but to process it you can use X-MCFX Volver or the MConvolutionEZ from MeldaProduction, both free :
http://www.angelofarina.it/X-MCFX.htm
https://www.meldaproduction.com/MFreeFXBundle
jm duchenne is offline   Reply With Quote
Old 05-27-2021, 08:02 AM   #6
Kewl
Human being with feelings
 
Join Date: Jan 2009
Location: Montreal, Canada
Posts: 81
Default

Quote:
Originally Posted by Jensus View Post
Is it possible at all to create a 16 channel IR file and use it with a 360 panner in any software today?
A bit of work, but, yes.

For the IR capture and processing, I would use Logic Pro's Impulse Response Utility with the "Quadraphonic" preset for an A-Format mic or "Quadraphonic B-Format encoded" preset for a B-Format microphone. Both have 16 IRs.

For the convolution with the IRs, I would probably use X-Volver Essential. Signal flow:

For A-Format microphone IRs:
B-Format -> Decode to position of emitters -> A-Format IRs convolution -> B-Format encoding

B-Format microphone IRs:
B-Format -> Decode to position of emitters -> B-Format IRs convolution
Kewl is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -7. The time now is 07:08 AM.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2021, vBulletin Solutions Inc.