On 2017-01-07, Stefan Schreiber wrote:
- If the listener doesn't use some decoder, UHJ is listened to as <
stereo >. (You are delivering surround sound, but the listener
actually doesn't notice.)
Actually se does notice. That's because UHJ was rather well designed to
be a compatibility format. Sure, you don't get all out of it without a
decoder. But it's still designed to make somewhat of an impression even
without one.
I mean, there's a *reason* why the encoding locus is as slanted as it
is, why the phasing is like it is, why the backstage is attenuated, and
so forth. From the get go, BHJ's meant to work both with a decoder, and
without; it's meant to faithfully reproduce as much of the pantophonic
goodness over basic stereo as it possibly can.
What *I* find peculiar is how well it works binaurally. That wasn't the
original optimization frontier of UHJ at all. The compatibility frontier
was for frontal stereo...and yet it sounds pretty darn good even over
headphones. ;)
- If you already use some binaural decoder, you could apply some
3/4-channel Ambisonics to binaural decoder anyway.
Like what? I haven't seen one easily downloadable, push-button ambisonic
thingy in my life at least.
On this list, among severe professionals and afficionados, it's easy to
think you can just "install a decoder". But in the wild, for the rest of
the world, the idea of a "decoder" is still a mystery, and a pain in the
ass. Something people -- even I -- won't put up with.
Not even on-list everybody has a perfectly set up sonic workflow, in
which you can just plug in your decoder of choice. In fact I suspect
most of the folks even here are like me: not capable or willing of
having even a basic four-way system. If I'm right, then for most people
*even here*, the idea of "just plugging in a decoder" is pure fancy.
- 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*. It's as far psychoacoustically optimized for that role, at least
given it's underlying Makita theory, as any passive, linear matrix *can*
be.
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. :)
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.)
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.
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.
--
Sampo Syreeni, aka decoy - de...@iki.fi, http://decoy.iki.fi/front
+358-40-3255353, 025E D175 ABE5 027C 9494 EEB0 E090 8BA9 0509 85C2
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