Ambisonics for VR in DP?

[BKK-OZ]

Just wondering if anyone was doing anything with ambisonics + DP?

I am working on a VR piece, with spatialised audio.

The trickie part is synchronising (both during production as well as playback/presentation) of spatial audio and video. Spatial audio in this instance needs to be dynamic, so that the sound field adjusts as the observer moves their head, giving the brain the right auditory signals to percieve positions of sounds.

YouTube's 360 video platform leverages ambisonics for spatial audio and it looks like other VR platforms are going to do the same.

The only DP-compatible ambisonic plugin that I am aware of is from Harpex:
http://harpex.net/download.html

[BKK-OZ]

Update...

I think I have found another (this one free!) plugin that could work in DP.
I haven't tested it yet.

You can find it here: http://www.tslproducts.com/soundfield/s ... bility-tab

[Shooshie]

It's been a long time since I dabbled in ambisonics, but from what I remember, it's a very incomplete theory. Applying it to a DAW seemed a pretty difficult task. Not sure if the actual thing really exists for a DAW. Any imitation would not be ambisonics.

Probably better with 5.1, or spatially enhanced stereo.

But then what do I know? There could have been a lot developed since then.

Shoosh

[BKK-OZ]

Yep, things have changed.

YouTube is adopting ambisonics, and there is also Dolby Atmos.

Then you also have things like: http://www.ambisonictoolkit.net for other hosts.

[Shooshie]

I'm curious, but don't have time at the moment to research it. How are the creating the holographic sound field? A central pickup? Some number of mics spread around?

I was an avid student of lightwave holography in the 1960s and 1970s, and had I not seen it and experienced it myself, I probably would not have guessed that it was possible. For that reason I realize that there may be special tricks for making it possible in audio, but I haven't seen it yet, myself. I used to read the work of Michael Gershon, who was an audio genius-type who was very much into ambisonics until his premature death. It seemed like the theory was sound, but bringing it into hardware was a challenge. If you know any of the particulars, I'd love a summation!

Yeah, yeah... look it up, Shooshie!

Shoosh

[cuttime]

I was an avid student of lightwave holography in the 1960s and 1970s, and had I not seen it and experienced it myself, I probably would not have guessed that it was possible.
Shoosh

Then are you as vexed as I when some reporter type refers to the Pepper's Ghost Illusion as a hologram? There are many companies out there that are promoting their services as holograms, when they are in fact angled glass reflections. (Sorry, off topic, I know.)

[Shooshie]

I was an avid student of lightwave holography in the 1960s and 1970s, and had I not seen it and experienced it myself, I probably would not have guessed that it was possible.
Shoosh

Then are you as vexed as I when some reporter type refers to the Pepper's Ghost Illusion as a hologram? There are many companies out there that are promoting their services as holograms, when they are in fact angled glass reflections. (Sorry, off topic, I know.)

Haha... yeah, unless a person actually knows what a hologram is, they are likely to confuse it with even those little grooved double-pictures we used to get in Cracker Jack boxes. Of course, now you get real holograms on credit cards; maybe Cracker Jacks! But knowing the science behind them makes them one of those mind-blowing quantum reality things. Not an optical illusion, but an actual recreation of the state of all waves passing through that point at a given time. It's just unreal. (sorry... encouraging off-topic conversation!)

Ambisonics seeks to do something like that in audio. That's a thing I pondered for years before I ever heard of ambisonics, and I used to draw possible scenarios for capturing it in my journals. I don't think they had gotten much further than I had when I stopped keeping track of it. Unlike light waves, atmospheric atoms in a vibrating wave do not share the quantum properties of actual light waves. Or... rather... they don't do so on a level that we readily perceive as sound. It may be quite a trick to get something truly "holographic" in a 360°^2 vibrating atmospheric space.

Shoosh

[BKK-OZ]

I'm curious, but don't have time at the moment to research it. How are the creating the holographic sound field? A central pickup? Some number of mics spread around?
Shoosh

Happy to share what I am learning.
Not an expert on ambisonic mics - they are usually a tetrahedral configuration, more and more seem to be coming onto the market.

For some info on ambisonics, see below...

Here is a good overview of ambisonics, though a little out of date in terms of implementations in the last year:
http://www.tvtechnology.com/resources/0 ... dio/277637


Spatial audio landing page for YouTube, shows current overview:
https://support.google.com/youtube/answ ... 9?hl=en-GB

From YouTube, Ambisonic spec, somewhat technical, but probably the closest thing we have to a 'standard':
https://support.google.com/jump/answer/6399746?hl=en

More plugins, ambisonic software (not yet tested by me in DP):
http://www.blueripplesound.com/products/toa-core-vst
http://www.brucewiggins.co.uk/?page_id=78

[Shooshie]

After reading some of these, I am not convinced that any real breakthroughs have occurred. It's one of those things that would require going through all they have done and refuting or discussing things on a point by point basis, showing how each might be improved or why it isn't quite as they are implying, and I'm not prepared to do that right now. It's my opinion against theirs, but I would recommend treating ambisonics with the same wait and see attitude we used to reserve for Monster Cables and the like, until we can see independent tests. Right now it is questionably applying the science in ways that seem more attuned with charging a lot of money than producing unique results.

I may be wrong. Not having access to their software, there may be some brilliant solutions that I didn't think of, but I can see what's going into it, and I have some idea of what needs to come out, and it's not what I would call ambisonics, or at least not an efficient approach for ambisonics using that method. But it IS expensive!

Shooshie

[EMRR]

I've been using the free Soundfield plug in DP. It seems to work, but is tricky to sort out the proper routing in DP. My usage so far has been native B-format to stereo output rather than full surround.

[dix]

Presumably, to get going with VR audio I would first need VR goggles, right? Can anyone recommend the software and hardware I need. ...i'm an iPhone 6S user btw.

[BKK-OZ]

I've been using the free Soundfield plug in DP. It seems to work, but is tricky to sort out the proper routing in DP. My usage so far has been native B-format to stereo output rather than full surround.

I couldn't figure out how to route inputs - what is the secret?

[EMRR]

Maybe these will help, though there are some confusing aspects in what I was doing at the time (comparing AND decoding M/S stereo back to individual elements). Look at busses 10-13. You must have an interface with 4 outputs for the plug to work, even for stereo fold down, so you can assign a surround bus.

https://c1.staticflickr.com/9/8599/2828 ... 2325_o.png

https://c1.staticflickr.com/9/8896/2828 ... dd2d_o.png

[Shooshie]

To make a mic truly ambisonic, wouldn't you have to make a 3-axis MS arrangement using 3 figure-8s and a central omni, instead of a cardioid, as the reference mic? Then, a 3-D decoder would basically be a set of 3 gain controls tied into a tetrahedron arrangement in a rotating 3-axis display, that worked together as you move the reference point around the tetrahedron? Then you'd have to place these pretty much everywhere in a room.

What I'm seeing in the examples you've posted is a set of four cardioids per mic, and I cannot see any way that could be processed as true ambisonics. I haven't read all their research or anything, but it just doesn't seem like they are on the right trail. I can't see Michael Gerzon approving of it, were he still around. But maybe they've done something I'm not aware of. (that wouldn't take much, most likely!)

Yeah, I know I already said something like this before, but it didn't seem to generate any response. I'm just saying, is this ready for people to spend their hard-earned cash on what appears to be nothing more than a fancier version of "quadrophonics" from the 1970s? You guys seem content to be trying it out, and not much interested in someone saying "nay," but I'm just rather cautious of overly simplistic hardware making such big claims in audio. Too many monster cables and induction bricks enhancing digital signals for the best sound ever have kind of made me quick to call bullsh•• on stuff that doesn't lay their science out front for everyone to see. My BS detector is in the red on this one.

Shooshie

[EMRR]

I'm doing horizontal only surround downfolding to stereo, it simply lacks the vertical element. Note the lack of the vertical element signal in the examples. I personally have no interest in full 3D ambisonic or VR, nor even surround, but the plug will get you there for any of them. I'm running MS ribbons with an omni addition as single point pickup for acoustic musicians in the round, sometimes at live events, sometimes studio. It gives a great degree of control while maintaining single point 'you are there' perspective.


https://en.wikipedia.org/wiki/Ambisonics:

Ambisonics can be understood as a three-dimensional extension of M/S (mid/side) stereo, adding additional difference channels for height and depth. The resulting signal set is called B-format. Its component channels are labelled W for the sound pressure (the M in M/S), X for the front-minus-back sound pressure gradient, Y for left-minus-right (the S in M/S) and Z for up-minus-down.

The signal corresponds to an omnidirectional microphone, whereas are the components that would be picked up by figure-of-eight capsules oriented along the three spatial axes.

Since the components of first-order Ambisonics correspond to physical microphone pickup patterns, it is practical to record B-format directly, with a collection of coincident microphones: an omnidirectional capsule, one forward-facing and one left-facing figure-of-eight, yielding the W, X and Y components. This is referred to as a native or Nimbus/Halliday microphone array.

The primary difficulty inherent in this approach is that high-frequency localisation and clarity relies on the diaphragms approaching true coincidence. By stacking the capsules vertically, perfect coincidence for horizontal sources is obtained. However, sound from above or below will suffer from subtle comb filtering effects in the highest frequencies.

Native arrays are most commonly used for horizontal-only surround, because of increasing positional errors and shading effects when adding a fourth microphone.