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Old 07-24-2016, 02:15 PM   #1
lossius
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Default Ambisonic Toolkit for Reaper - 1.0.0.b9

ATK for Reaper v.1.0.0.b9 is now available. Some key changes:

- Binaural decoders at all sample rates
- New encoders and decoders for bridging between FuMa and AmbiX (useful for VR authoring)

And two changes that breaks backwards compatibility:

- Azimuth is now positive in counter-clockwise direction
- Quad decoder now has 4 channels out only

More details can be found here:

http://www.ambisonictoolkit.net/publ...r-1.0.0b9.html
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Old 07-24-2016, 02:47 PM   #2
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Thank you, Trond!
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Old 07-24-2016, 06:53 PM   #3
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Wonderful stuff Trond! Another big thank you.

I've literally just finished setting up and testing my first 3D cube using mostly Auratone 5C cubes and have been using your ATK (and the Periphonic 3D decoder) for testing and listening. I made another post about that and just replied to it with some details about the cube array.

I'm planning on starting some Ambisonic mixes of my own in the next few weeks so your updates are perfect timing, particularly given the azimuth fix. Given I haven't done any B format mixes just yet, I don't have to worry about backwards compatibility.

A quick question about the periphonic decoder... Is the elevation angle the angle between the horizontal listening plane (midway between the upper and lower ring in my current setup) and the top and bottom speaker rings?
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Old 07-24-2016, 11:59 PM   #4
lossius
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Quote:
Originally Posted by ReaDave View Post
I've literally just finished setting up and testing my first 3D cube using mostly Auratone 5C cubes and have been using your ATK (and the Periphonic 3D decoder) for testing and listening. I made another post about that and just replied to it with some details about the cube array.
Cool, I'll check that post out.

Quote:
Originally Posted by ReaDave View Post
A quick question about the periphonic decoder... Is the elevation angle the angle between the horizontal listening plane (midway between the upper and lower ring in my current setup) and the top and bottom speaker rings?
Yes, it's the elevation angle from horizon to the upper ring, and similar to the lower ring. So at 0 deg both rings would be in the horizon (which doesn't make much sense) and at 90 degrees the rings have collapsed to be just above and below you (which doesn't make sense either). So it's very likely that you'll work with an angle somewhere in between.

There is a small visualisation in the GUI of the elevation angle, in between the two circles and a little to the right.

I should mention that the Periphonic 3D decoder does work correctly yet. When porting the code from the SuperCollider version of ATK I failed to realise that the matrixes used are to be "pseudo-inversed". I have tried and used the Periphonic 3D decoder in it's current state myself, and get quite good results, but according to Joseph Anderson it will sound better (and be more correct with respect to Gerzon's ideas about ambisonics) when I have added the pseudo-inverse. This is tracked in relation to #2, #4 and #5 in the issue tracker:

https://github.com/ambisonictoolkit/atk-reaper/issues

I hope that it won't take to long before I get around to address this, as it's one of the main tasks left before ATK can be properly released, but I have a pretty packed schedule thought September.
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Old 07-25-2016, 10:46 AM   #5
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Thanks again Trond. Much appreciated. What you mentioned about the elevation control is pretty much what I figured it was for.

Regarding the pseudo inverse situation, do you have any information about what that does and how not including it will affect my listening tests? I didn't see much of a description about that in the tracker.
I have been directly comparing your cube decoder with Bruce Wiggins one and, from the limited time I've had so far and my less than optimal current speaker configuration, I prefer the sound of yours. It seems to provide better rear localization. I did have to reverse the polarity of the two lower rear speakers though for the sound localization to work well enough. As I mentioned in my other thread though, that could be either an amplifier issue (I'm running those speakers from a different amplifier) or it could be because those two speakers are not Auratones and I've had to EQ them to get them timbrally similar.

Or perhaps this is related to the pseudo inverse thing you're speaking of?
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Old 07-25-2016, 01:47 PM   #6
lossius
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Quote:
Originally Posted by ReaDave View Post
Regarding the pseudo inverse situation, do you have any information about what that does and how not including it will affect my listening tests? I didn't see much of a description about that in the tracker.
I have been directly comparing your cube decoder with Bruce Wiggins one and, from the limited time I've had so far and my less than optimal current speaker configuration, I prefer the sound of yours. It seems to provide better rear localization. I did have to reverse the polarity of the two lower rear speakers though for the sound localization to work well enough. As I mentioned in my other thread though, that could be either an amplifier issue (I'm running those speakers from a different amplifier) or it could be because those two speakers are not Auratones and I've had to EQ them to get them timbrally similar.

Or perhaps this is related to the pseudo inverse thing you're speaking of?
The PseudoInverse thing might not be clear from the tracker, but at least I myself understand what it's about when looking at it... ;-)

The idea with ambisonics decoding is that it is very straight forward when all speakers are positioned at equal angular distance. In 3D this only happens if the speakers are laid out according to one of the platonic solids. My guess is that Brice Wiggins Cube decoder is using one of these shapes, and if so, the vertical distance between upper and lower ring has to be the exact same as the distance between front and back speakers in order for the decoder to work properly. This might be why you are not getting satisfactory results from it.

If you need to decode to irregular speaker layouts, some kind of "best fit" solution need to be applied. The PseudoInverse trick is that it asks what it would sound like if you had sound sources coming from the direction of each of your speaker. It then inverts this so that what started out as an encoder of a number of planewaves instead becomes a decoder. I´m not sure exactly how that will sound and how it will differ fro the current implementation, but I trust Joseph when he says that it will improve the decoder. But that being said, I agree with you that it works fairly well already, I have been surprised by how good it sounds when trying out with two rings of 8 speakers at LABRI in Bordeaux in May. And I'm looking forward to test with proper PseudoInverse implementation as well.
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