Sampo Syreeni wrote:



- Backward-compatible (to stereo) forms of Ambisonics are very probably possible.


They are not "probably possible". That's what the BHJ version of UHJ *is*.

Yes. But you still have to put L/R + 1 or 2 ext. channels into some < stereo > MP3 or AAC file. Our aim would be to be backward compatibility to common file and stream stereo formats. This is not completely trivial, but can be done. (Extension channels "buried" in file or container format. We don't want to break existing stereo decoders...)

It's as far psychoacoustically optimized for that role, at least given it's underlying Makita theory, as any passive, linear matrix *can* be.

UHJ was always a hierarchy scheme. Even so you have to find some space for T and Q channels. It is all just about some "practical space problems", not Makita theory itself... Just IT and standard related stuff, not math! ;-)


I have proposed this idea some time ago. (At 1st order the proposal is based on 3/4 channel UHJ, so on some LR-TQ channel "stereo core + extension" scheme. This concept could probably be extended to HOA, as well.)


Yes, it'd be interesting to see how the compatibility format idea might be extended to more modern settings. I think I've talked about that for a bit in the past, myself. But of course, I've just jotted out something; it'd be nice to see it fleshed out for real. Especially in the original Gerzon vein of building out a complete, mutually compatible, extensible hierarchy of both channel encodings, and speaker playback formats. :)

Agreed! (What?!)  :-)


Isn't it a bit late for 2-channel UHJ decoders anyway? Some radio broadcaster already could try to apply some < multiformat > surround to binaural decoders on the "customer" side.


Well, do they do anything as nice as BHJ right now? Do they even try? Do they even have something like this on their future map? I don't think so. As such, I for one -- as a newbie on-list, and perhaps even a pure theoretical buff with nigh to none practical experience -- still think the ambisonic way remains useful. Highly so, even if the basic framework could and does benefit from newer innovation. (Say, my alltime favourite decoder, DirAC, and its newer, higher order, and more principled derivatives.)

DirAC has the problem that it currebtly can be used "just as research" tool. (I won't discuss this here. But you know this as well as I do. )



5.1 and Ambisonics should/could be both supported, and maybe more formats.


That is an interesting line of thought for me as well. Undoubtedly for many on-list. How do you really bridge common discrete formats such as 5.1 or 7.1 with the ambisonic framework? Also, in the high audiophile, research mindset which engenders HOA and (as shown by Daniel and Nichols to be in the limit equivalent, I seem to remember) WFS.

I think the proper formulation would start from idealized far field (planewave) response, angularly evened out to whatever ambisonic order we choose to work with. In fact I believe when I and Martin Leese did our little thingy with OggPCM channel formats, we were working on that precice if implicit assumption: that the directionality inherent to most discrete formats could be modelled within the ambisonic framework as distant, infinitely precise in direction, sources, to be folded down into an ambisonic soundscape, and from there on to be (optimally) decoded as usual.

Or maybe so that knowing some source is tagged as a point source, it might be separately decoded via something like VBAP, while the rest of the field is reproduced by ambisonic principles. Dunno.

Maybe. But before we "just" would need some good binaural decoder for some standard surround formats; 5.1 and FOA surely included.

Until 2morrow, and many thanks for your thoughtful and constructive posting! (I have to think about this quite a bit more....)

Stefan


-----------------------


Stil, be as it may, the idea of folding all of the current spatial audio into one big theory isn't new. I certainly didn't invent it, nor did anyone on this list. There's a lot of history behind the idea, perhaps not starting even with *Gerzon* himself. We'd all like to see the theory developed more fully, but I think we can all agree, it's not exactly a new invention, or ours, even if we were to be the ones to bring it to its fruition.

(If format wars are not necessary from a modern perspective, we should not try to continue some partially imagined conflict.


(Software) format wars go away once there is simplistic, free, open sourced software to "just do the thing any which way and convert". Cf. Eric de Castro Lopo's libsndfile; it pretty much took away any problem with differing sound file formats, once it reached its current maturity.

So, I'd say that the same would happen with ambisonic, if we had a free, comprehensive library to deal with our favourite sound system. Well documented, proven in practice, and made easy to integrate.

I believe we can all agree on what that sort of thing should look like. What the interfaces should be, and so forth. But to date nobody's actually implemented the thing. Parts of it, sure. Even multiple times over, for fame and other individual reasons. But I think it still remains the fact that we don't have "that one definitive, all-encompassing, one, ambisonic library", which everybody *just* *likes* *to* *use*, and then *does*.

I believe that's what'd settle the matter in the end. Not abstract theoretisising, or even particular efforts to implement some forms of the system, but a concerted effort to put all of the knowledge the ambisonic community has, into one easily used, well-generalized, and well-maintained, piece of code.

Ambisonics has some clear advantages in the areas of AR/VR and 360º video. So some natural application cases finally exist.)


Yes. If you want in-the-wild examples there, take a look at Peter Hajba's work (aka Skaven, of FutureCrew, in the demo circles). And of course then Ville Pulkki and his research group's work at Aalto University. Headtracked, simultaneous audio and "VR" is *awesome*! :D

Even HTML5 surround  decoders are possible by now:

http://hyperradio.radiofrance.fr/son-3d/


Nice. Will look into that.

Marc Lavallée presented one online player/decoder for XYW recordings.

Now somebody would "just" have to do some integration.


Yes! Who would be that someone then? ;)

funding from the European Commission under the Horizon 2020 programme


Hmm. An interesting idea, at least for me... Would it be possible to get that "one, definitive, free and opensource ambisonic library" I alluded to above, done with public money? Some invention grant from the EU or whatnot?

Because, I mean, such funding sources like demos. The ambisonic community has some darn impressive demos already, to just give out. So, such funding -- even if we all know where it once went with the NRDC -- might be rather readily available. If only somebody bothered to jot down a well-thought out grant proposal.

This really oughtn't be rocket surgery...

ORPHEUS will deliver a sustainable solution, ensuring that workflows and components for object-based audio scale up to enable cost-effective commercial production, storage, re-purposing, play-out and distribution.


"Object based audio." Yes, well, it might be that nowadays with all of the power of modern processors, you can actually do mixed and synthetic audio at what amounts to "infinite order" in ambisonic terms. Pure point sources, panned around.

But in at least two respects the ambisonic theory/framework still reigns supreme.

First, you can't get past the first, most basic theorem of ambisonic decoding: if you want to decode *anything*, including those point sources of today, into a sparse speaker array, you'll have to psychoacoustically optimize what you're doing. Then even the most basic Makita theory Gerzon started out with tells you, you simply cannot do things like VBAP without losing isotropy.

Fine, maybe you don't want that every time. Maybe you want to do stuff which risks exposing speaker locations, as the price for more spatial definition. That's certainly what Dolby does right now with Atmos. But then we have point two:

Secondly, and most forcefully, there is absolutely no other way to capture a live soundfield faithfully other than some version of ambisonic. All with its unique soundfield mic designs. Even if you somehow conventionally miced and mixed stuff just right, so as to mimic a live soundfield, there *still* is no extant framework within which to fully process directional sound, absent ambisonic. It's all you've got -- and because of its underpinnings, all you'll ever have, with complete mathematical certainty.

As such, if this shit was to be packaged in a neat, free, open library, in its most general and generous form, I believe it'd easily become the new norm. Because there just wouldn't be any alternative to the comprehensive theory and practice which goes along with it.

I think the only question is "whodunnit". ;)

Of course they could (or should?) start to implement 5.1 and Ambisonics decoders firstly. But < who > would fund < this > stuff?!


Then, does anybody actually need to fund this, even? All of the stuff we need is already there. It just needs to be packaged right. Even the hardest part, the nonlinear decoder optimizer code, already exists, at least in Benjamin, Lee and Heller's Tabu search code (which is general as fuck). And all of the movers and shakers pretty much are on this list, or once removed.

I don't think it's even about funding. It's about simple organization. Perhaps with a few egos soothed via visible credits, and such. But not much more.

"Wait until 2020. All will be good by then." (It is also some classical Ircam strategy to point to the benefits of the < next generation >. We never will be < there > , but never mind! :-D )


As dyed-in-the-wool individualist and one nasty libertarian, I'd say *still* fuck IRCAM. Seriously. it's a piece of age-old French dirigisme, before it ever was a place of learning and innovation. I feel sorry for the (grantedly many) excellent, sonically and signal processing minded individuals who had the unfortune to land in said hellhole. Had they ever seen a community like that of MIT or Caltech, they'dd have shat on IRCAM's very name, and after that done *much* more for themselves and humanity than they now have.

Now the modern likes of Serre et al. are doomed to basically live in a black hole. An insular island removed from the scientific and technical mainstream. People kind of fall into IRCAM, because of its attractions. Once they do, they fall beyond that particular, institutional, event horizon. Nothing ever comes out from there, we don't know what the fuck goes there beyond their (rather impressive) toys, and what little comes out is...pardon me, garbled French.

So: We don't have to be < too > conservative. (We also don't have to wait 'til "2020" to start with something.)


Well agreed.

P.S.: And quadraphonic formats are maybe interesting - but quite obviously surround history. Some recordings still exist, but there won't be anything recent or new "stuff" around.


Yes. But history is still worth preserving. And I don't just mean on the recording side. I also think the theory and the practice of quadraphonic technology is worth preservation; if only because it serves as a counter-example to the more developed theory which is ambisonic.

"Alice's Adventures In (3D Audio?) Wonderland".


I can remember listening to this play on BBC Radio 3/4 several times, great stuff.


You're privileged in having (had?) access to this sort of stuff. Around here, and in my age cohort, none of that experimental radio stuff has *ever* been around. I grew up thinking stereo is all there could possibly be.

I still have some off-air recordings of the BBC's Matrix H system. Never tried to decode them but they have a pleasing surround sensation when listened to on headphones. Must have been the mic. placements ??


Richard, mind digitizing and sharing them? I'd be rather interested in the stuff.


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