Re: [Sursound] format convention of Ambisonic Sound Library Files

[Sampo Syreeni]

On 2022-05-25, Fons Adriaensen wrote:

I am still not too sure if even now things are standardised enough 
for anyone to write a fresh file format for it that pleases everyone.


It doesn't have to please anybody at all. It just needs to work, and be 
implemented in a widely known and FLOSS library. Repetto's Libsndfile 
always comes to mind here, from discussions on the musicdsp list.


Suffice it to say, such things can't just be written,they have to be 
implemented and tested, e.g. on vast tiered speaker layouts which 
very few people have access to.


I'd argue that library-wise, even a very basic decoder would do most of 
the lifting. Once the foot is in the door, then developers would jump at 
the opportunity to better their wares.


So what's missing from the base ambisonic toolchain? Not the file 
format, because AmbiX/CAF does just fine and its extended format *more* 
than fine. As Fons just laid it out.


What's missing is plug-and-play integration with Libsndfile and plain 
binary, a basic shelving n:th-order decoder, and n:th order streaming 
primitives for processing, as an integrated and optimized FLOSS package, 
written in C. Ported to the main architectures used out there for sound 
playback and recording, so x86/64, ARM, and maybe Verilog/VHDL for 
FPGL/ASIC work. If you were to be funny about it, an MPI implementation 
for massively parallel research work.



And of course it will need to use a 64bit-friendly file format too...


Which CAF is. RIFF can be so as well, but not *nearly* as neatly.

Ambix seems to be the de facto standard today, except that instead of 
the required CAF container most people seem to use the same channel 
order and gains in a WAVEX file. Which in turn means that the 
'extended' format is not available as it depends on CAF's UUID chunck.


Obviously RIFF, as in WAVEX, is a chunked format as well. It's well 
capable of carrying a UUID-kinda optional chunk. In fact, IFF/RIFF are 
the progenitors to CAF/MPEG-4 BMFF as well as WAVEX/RF64. The nested TLV 
structure, akin to even ASN.1, is fully retained.


A problem with the Ambix spec is that the internet never forgets, and 
if you search for it you could easily find the now invalid original 
document, or a version of the same with 'corrections' that make it 
hard to read and interpret.


None of that matters if you just go and implement the thing and spread 
your code around. "Code is law." Not the spec.


What is IMHO missing in the Ambix format is an optional UUID chunk 
that would contain the same info as a broadcast WAV, and in exactly 
the same format.


Ought to be simple enough to add as side metadata, right? Also usable by 
any part of the toolchain I outlined above.


What I can't advocate for are tons of different options for ordering, 
interlacing and bitwidths. Those are impossible to implement 
efficiently, especially in hardware. What you need is a fixed global 
channel order, from which something can be detracted. You can't do that 
by including null channels, because they will consume memory bandwidth 
as well. What you can do is specify a certain order and then mask 
channels out of it; this is what was done in the USB specification, and 
it's even more doable within some derivative of AmbiX.


It's also what we tried to do with Martin Leese when we specified the 
(from the beginning defunct) Ogg Channel mapping machinery ( 
https://wiki.xiph.org/OggPCM ). That piece of work tried to order all of 
the possible multichannel types by way of the existing bit masks having 
to do with individual channels. So basically by their quantized 
directional angle.


...but not quite so in toto, because there are plenty of channel 
definitions in use with extra semantics. E.g. the THX standard wants to 
have side back channels which are front-back dipoles, with no direct 
sound towards the central listener. This sort of thing is almost 
impossible to describe within the ambisonic framework, without including 
a high order room model. And besides, semantically, the minimum model is 
already encapsulated by the *intention* of the emitter being there: 
it's left back/right emitting field with no directed sound, intended to 
excite diffuse room modes from there, despite the size of the 
auditorium. It's rather difficult to exhibit something like that 
precisely in the ambisonic framework, yet it's still something you have 
to handle in cinematic audio, so we/I just left it in there to be worked 
out by the decoder.


Such metadata is really essential for some users. It could easily be 
added without breaking anything.


So why not just copy the format and throw it into a chunk? That's what 
TLV-formats like CAF are ment to do? Obviously since it's metadata, it 
should go before the massive data proper. But otherwise, why not just 
throw it in there, as an option? It doesn't cost anything, basically, 
gauged against the gigabytes or even terabytes of multichannel audio, it 
works just well with the extensibility 

Re: [Sursound] format convention of Ambisonic Sound Library Files

[Fons Adriaensen]

On Wed, May 25, 2022 at 08:45:42AM +0100, Richard Dobson wrote:

> I am still not too sure if
> even now things are standardised enough for anyone to write a fresh file
> format for it that pleases everyone. Suffice it to say, such things can't
> just be written,they have to be implemented and tested, e.g. on vast tiered
> speaker layouts which very few people have access to. And of course it will
> need to use a 64bit-friendly file format too...

Ambix seems to be the de facto standard today, except that instead of the
required CAF container most people seem to use the same channel order and
gains in a WAVEX file. Which in turn means that the 'extended' format is
not available as it depends on CAF's UUID chunck.

That's a shame, because CAF is really the cleanest audio file format
available today [1]. Advantages are:

- no history of incompatible 'vendor extensions',
- 64-bit size, in practice no limit on duration,
- it can be extended without breaking the official specs.

A problem with the Ambix spec is that the internet never forgets,
and if you search for it you could easily find the now invalid
original document, or a version of the same with 'corrections' 
that make it hard to read and interpret.

The one at 



seems to be OK.

What is IMHO missing in the Ambix format is an optional UUID
chunk that would contain the same info as a broadcast WAV, and
in exactly the same format. Such metadata is really essential
for some users. It could easily be added without breaking anything.


[1] Except for the channel description chunk which is the usual
mishmash of everything the authors could imagine, and still not
capable of describing arbitrary channel uses or just saying 
'undefined'. Luckily it is not required for the Ambix format.

-- 
FA

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Re: [Sursound] format convention of Ambisonic Sound Library Files

[Richard Dobson]

Welcome to my world - as it used to be! The ring-pass-not is that word 
'standardised". My AMB Wavex-based file format is now 22 years old 
(FuMa, up to third-order). People have long moved on - basically as soon 
as that was published, everyone here started arguing about all the other 
information that should be included, alternative standards, channel 
order, higher orders,  filters, irregular layouts, the works. I am still 
not too sure if even now things are standardised enough for anyone to 
write a fresh file format for it that pleases everyone. Suffice it to 
say, such things can't just be written,they have to be implemented and 
tested, e.g. on vast tiered speaker layouts which very few people have 
access to. And of course it will need to use a 64bit-friendly file 
format too...


A reminder, for anyone feeling nostalgic:

http://www.rwdobson.com/bformat.html

Richard Dobson



On 24/05/2022 23:13, Sampo Syreeni wrote:

On 2022-05-24, Alan Kan wrote:

Ah… it seems one has to actually click on the file to see that detail. 
I was downloading from the list page.


Why not embed the a standardised format descriptor into the file itself? 
Most formats permit that. In fact that's what we've been doing all along 
e.g.in RIFF WAVE.

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Re: [Sursound] format convention of Ambisonic Sound Library Files

[Sampo Syreeni]

On 2022-05-24, Alan Kan wrote:

Ah… it seems one has to actually click on the file to see that detail. 
I was downloading from the list page.


Why not embed the a standardised format descriptor into the file itself? 
Most formats permit that. In fact that's what we've been doing all along 
e.g.in RIFF WAVE.

--
Sampo Syreeni, aka decoy - de...@iki.fi, http://decoy.iki.fi/front
+358-40-3751464, 025E D175 ABE5 027C 9494 EEB0 E090 8BA9 0509 85C2
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Re: [Sursound] format convention of Ambisonic Sound Library Files

[Alan Kan]

Ah… it seems one has to actually click on the file to see that detail. I was 
downloading from the list page. Thanks for pointing that out Aaron.

From: Sursound  On Behalf Of Aaron Heller
Sent: Tuesday, 24 May 2022 7:28 AM
To: Surround Sound discussion group 
Subject: Re: [Sursound] format convention of Ambisonic Sound Library Files

Each file's page indicates the convention; all the ones I've looked at have
been AmbiX, but I've only looked at a small fraction of the files.

The ones I have downloaded have names that appear random, like
Acdb7b0a20a799bde7257.wav
... no obvious indication of the convection used.

It's a great resource, but it would certainly be better if the filenames
were more mnemonic, as well as indicating the channel convection in use.

Aaron Heller




On Mon, May 23, 2022 at 5:43 AM Jack Reynolds 
mailto:jackreynolds...@gmail.com>>
wrote:

> As far as the know each file has the format in the file name.
>
> J
>
> Sent from my iPhone
>
> > On 23 May 2022, at 13:16, Alan Kan 
> > mailto:alan@mq.edu.au>> wrote:
> >
> > Hi,
> >
> > I was wondering if anyone could tell me whether the audio examples in
> the Ambisonic Sound Library on 
> https://library.soundfield.com/<https://library.soundfield.com> are in
> FuMa or AmbiX format? I couldn't find this detail on the website.
> >
> > Thanks
> >
> > Alan
> > ---
> > Dr. Alan Kan, PhD (he/his/him)
> > Research Fellow
> > School of Engineering<
> https://www.mq.edu.au/faculty-of-science-and-engineering/departments-and-schools/school-of-engineering>
> | Macquarie University
> > Level 1, 50 Waterloo Road, Macquarie Park, NSW 2113, Australia
> > T: +61 (2) 9850 2247
> >
> > ECHO Lab | Macquarie University Hearing<
> https://www.mq.edu.au/about/about-the-university/vision-strategy/other-university-initiatives/hearing>
> | Australian Hearing 
> Hub<https://hearinghub.edu.au/<https://hearinghub.edu.au>>
> > Room 1.626, 16 University Avenue, Macquarie University, NSW 2109,
> Australia
> > T: +61 (2) 9850 4520
> >
> > E: alan@mq.edu.au<mailto:alan@mq.edu.au>
> > W: 
> > www.mq.edu.au/research/echolab<http://www.mq.edu.au/research/echolab<http://www.mq.edu.au/research/echolab%3chttp:/www.mq.edu.au/research/echolab>>
> | researchers.mq.edu.au/en/persons/alan-kan<
> https://researchers.mq.edu.au/en/persons/alan-kan>
> > L: 
> > www.linkedin.com/in/alan-kan<http://www.linkedin.com/in/alan-kan><http://www.linkedin.com/in/alan-kan<http://www.linkedin.com/in/alan-kan>>
> >
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Re: [Sursound] format convention of Ambisonic Sound Library Files

[Aaron Heller]

Each file's page indicates the convention; all the ones I've looked at have
been AmbiX, but I've only looked at a small fraction of the files.

The ones I have downloaded have names that appear random, like
  Acdb7b0a20a799bde7257.wav
... no obvious indication of the convection used.

It's a great resource, but it would certainly be better if the filenames
were more mnemonic, as well as indicating the channel convection in use.

Aaron Heller




On Mon, May 23, 2022 at 5:43 AM Jack Reynolds 
wrote:

> As far as the know each file has the format in the file name.
>
> J
>
> Sent from my iPhone
>
> > On 23 May 2022, at 13:16, Alan Kan  wrote:
> >
> > Hi,
> >
> > I was wondering if anyone could tell me whether the audio examples in
> the Ambisonic Sound Library on https://library.soundfield.com/ are in
> FuMa or AmbiX format? I couldn't find this detail on the website.
> >
> > Thanks
> >
> > Alan
> > ---
> > Dr. Alan Kan, PhD (he/his/him)
> > Research Fellow
> > School of Engineering<
> https://www.mq.edu.au/faculty-of-science-and-engineering/departments-and-schools/school-of-engineering>
> | Macquarie University
> > Level 1, 50 Waterloo Road, Macquarie Park, NSW 2113, Australia
> > T: +61 (2) 9850 2247
> >
> > ECHO Lab | Macquarie University Hearing<
> https://www.mq.edu.au/about/about-the-university/vision-strategy/other-university-initiatives/hearing>
> | Australian Hearing Hub
> > Room 1.626, 16 University Avenue, Macquarie University, NSW 2109,
> Australia
> > T: +61 (2) 9850 4520
> >
> > E:  alan@mq.edu.au
> > W: www.mq.edu.au/research/echolab
> | researchers.mq.edu.au/en/persons/alan-kan<
> https://researchers.mq.edu.au/en/persons/alan-kan>
> > L: www.linkedin.com/in/alan-kan
> >
> > [cid:image003.png@01D86EF2.BAFAA8C0]
> >
> > CRICOS Provider 2J. ABN: 90 952 801 237.
> >
> > This message is intended for the addressee named and may contain
> confidential information. If you are not the intended
> > recipient, please delete the message and notify the sender. Views
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Re: [Sursound] format convention of Ambisonic Sound Library Files

[JJ Wiesler]

It is a bit confusing. I’m pretty sure many of them are in Aformat, as
captured by microphone which it does name in the title or listing info.

They have a nice free plugin to convert to various b formats

JJ

On Mon, May 23, 2022 at 5:43 AM Jack Reynolds 
wrote:

> As far as the know each file has the format in the file name.
>
> J
>
> Sent from my iPhone
>
> > On 23 May 2022, at 13:16, Alan Kan  wrote:
> >
> > Hi,
> >
> > I was wondering if anyone could tell me whether the audio examples in
> the Ambisonic Sound Library on https://library.soundfield.com/ are in
> FuMa or AmbiX format? I couldn't find this detail on the website.
> >
> > Thanks
> >
> > Alan
> > ---
> > Dr. Alan Kan, PhD (he/his/him)
> > Research Fellow
> > School of Engineering<
> https://www.mq.edu.au/faculty-of-science-and-engineering/departments-and-schools/school-of-engineering>
> | Macquarie University
> > Level 1, 50 Waterloo Road, Macquarie Park, NSW 2113, Australia
> > T: +61 (2) 9850 2247
> >
> > ECHO Lab | Macquarie University Hearing<
> https://www.mq.edu.au/about/about-the-university/vision-strategy/other-university-initiatives/hearing>
> | Australian Hearing Hub
> > Room 1.626, 16 University Avenue, Macquarie University, NSW 2109,
> Australia
> > T: +61 (2) 9850 4520
> >
> > E:  alan@mq.edu.au
> > W: www.mq.edu.au/research/echolab
> | researchers.mq.edu.au/en/persons/alan-kan<
> https://researchers.mq.edu.au/en/persons/alan-kan>
> > L: www.linkedin.com/in/alan-kan
> >
> > [cid:image003.png@01D86EF2.BAFAA8C0]
> >
> > CRICOS Provider 2J. ABN: 90 952 801 237.
> >
> > This message is intended for the addressee named and may contain
> confidential information. If you are not the intended
> > recipient, please delete the message and notify the sender. Views
> expressed in this message are those of the individual
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Re: [Sursound] format convention of Ambisonic Sound Library Files

[Jack Reynolds]

As far as the know each file has the format in the file name.

J

Sent from my iPhone

> On 23 May 2022, at 13:16, Alan Kan  wrote:
> 
> Hi,
> 
> I was wondering if anyone could tell me whether the audio examples in the 
> Ambisonic Sound Library on https://library.soundfield.com/ are in FuMa or 
> AmbiX format? I couldn't find this detail on the website.
> 
> Thanks
> 
> Alan
> ---
> Dr. Alan Kan, PhD (he/his/him)
> Research Fellow
> School of 
> Engineering
>  | Macquarie University
> Level 1, 50 Waterloo Road, Macquarie Park, NSW 2113, Australia
> T: +61 (2) 9850 2247
> 
> ECHO Lab | Macquarie University 
> Hearing
>  | Australian Hearing Hub
> Room 1.626, 16 University Avenue, Macquarie University, NSW 2109, Australia
> T: +61 (2) 9850 4520
> 
> E:  alan@mq.edu.au
> W: www.mq.edu.au/research/echolab | 
> researchers.mq.edu.au/en/persons/alan-kan
> L: www.linkedin.com/in/alan-kan
> 
> [cid:image003.png@01D86EF2.BAFAA8C0]
> 
> CRICOS Provider 2J. ABN: 90 952 801 237.
> 
> This message is intended for the addressee named and may contain confidential 
> information. If you are not the intended
> recipient, please delete the message and notify the sender. Views expressed 
> in this message are those of the individual
> sender and are not necessarily the views of Macquarie University and its 
> controlled entities.
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[Sursound] format convention of Ambisonic Sound Library Files

[Alan Kan]

Hi,

I was wondering if anyone could tell me whether the audio examples in the 
Ambisonic Sound Library on https://library.soundfield.com/ are in FuMa or AmbiX 
format? I couldn't find this detail on the website.

Thanks

Alan
---
Dr. Alan Kan, PhD (he/his/him)
Research Fellow
School of 
Engineering
 | Macquarie University
Level 1, 50 Waterloo Road, Macquarie Park, NSW 2113, Australia
T: +61 (2) 9850 2247

ECHO Lab | Macquarie University 
Hearing
 | Australian Hearing Hub
Room 1.626, 16 University Avenue, Macquarie University, NSW 2109, Australia
T: +61 (2) 9850 4520

E:  alan@mq.edu.au
W: www.mq.edu.au/research/echolab | 
researchers.mq.edu.au/en/persons/alan-kan
L: www.linkedin.com/in/alan-kan

[cid:image003.png@01D86EF2.BAFAA8C0]

CRICOS Provider 2J. ABN: 90 952 801 237.

This message is intended for the addressee named and may contain confidential 
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recipient, please delete the message and notify the sender. Views expressed in 
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controlled entities.

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