Discussion:
octofile release
(too old to reply)
Fons Adriaensen
2018-07-29 15:02:18 UTC
Permalink
Hello all,

Source code for octofile version 0.3.0 (linux) is now available at

<http://kokkinizita.linuxaudio.org/linuxaudio/downloads/index.html>

Octofile is the A to B format converter for Core Sound's Octomic.

A-format input can be 1,2,4 or 8 audio file(s) with resp. 8,4,2
or 1 channel(s) each, 44.1, 48 or 96 kHz.

Default output is a 2nd order Ambix file (CAF, SN3D, ACN) but the
legacy .amb or non-standard formats (e.g. Ambix in a .wav file)
are possible as well.

You will require a calibration file from Core Sound of course.

Ciao,
--
FA
Marc Lavallée
2018-07-29 17:46:04 UTC
Permalink
Easy to compile, support for FLAC, GPL3 license...

Thanks!

Marc
Post by Fons Adriaensen
Hello all,
Source code for octofile version 0.3.0 (linux) is now available at
<http://kokkinizita.linuxaudio.org/linuxaudio/downloads/index.html>
Octofile is the A to B format converter for Core Sound's Octomic.
A-format input can be 1,2,4 or 8 audio file(s) with resp. 8,4,2
or 1 channel(s) each, 44.1, 48 or 96 kHz.
Default output is a 2nd order Ambix file (CAF, SN3D, ACN) but the
legacy .amb or non-standard formats (e.g. Ambix in a .wav file)
are possible as well.
You will require a calibration file from Core Sound of course.
Ciao,
Fons Adriaensen
2018-07-29 18:20:15 UTC
Permalink
Post by Marc Lavallée
Easy to compile, support for FLAC, GPL3 license...
FLAC is supported for input only. The output is 9 channels,
and FLAC can't handle that. Never understood why they put
in that silly limit...

Ciao,
--
FA
Marc Lavallée
2018-07-29 18:44:22 UTC
Permalink
Excerpt from https://xiph.org/flac/faq.html#general__channels :

"FLAC supports from 1 to 8 channels per stream. Channels are only
grouped in FLAC to take advantage of interchannel correlation and to
define common channel assignments (like stereo L/R, 5.1 surround, et
cetera). When encoding a large number of independent channels it is
expected that they are coded separately and if required, multiplexed
together in a suitable container like Ogg or Matroska."

Marc
Post by Fons Adriaensen
Post by Marc Lavallée
Easy to compile, support for FLAC, GPL3 license...
FLAC is supported for input only. The output is 9 channels,
and FLAC can't handle that. Never understood why they put
in that silly limit...
Ciao,
Stefan Schreiber
2018-07-29 19:08:13 UTC
Permalink
Post by Marc Lavallée
"FLAC supports from 1 to 8 channels per stream. Channels are only
grouped in FLAC to take advantage of interchannel correlation and to
define common channel assignments (like stereo L/R, 5.1 surround, et
cetera). When encoding a large number of independent channels it is
expected that they are coded separately and if required, multiplexed
together in a suitable container like Ogg or Matroska."
Good info.

But this is a bit typical as an “answer”: HOW would you code many
channels separately in Flac (available sw to use etc.), and how to
multiplex into a “suitable container”?

Ok, no problem for anybody else... I am supposed to see! 😇

(https://xiph.org/flac/ogg_mapping.html

They don’t explain this at all, unless you take the faq answer as a
definition.)

Best,

Stefan

P.S.: They just have to extend (too) old definitions. 

As Fons says, the limit is a limit (paraphrasing Theresa May) - and
not justified from a current perspective. 
Post by Marc Lavallée
Marc
Post by Fons Adriaensen
Post by Marc Lavallée
Easy to compile, support for FLAC, GPL3 license...
FLAC is supported for input only. The output is 9 channels,
and FLAC can't handle that. Never understood why they put
in that silly limit...
Ciao,
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Marc Lavallée
2018-07-29 21:12:02 UTC
Permalink
Post by Stefan Schreiber
 "FLAC supports from 1 to 8 channels per stream. Channels are only
grouped in FLAC to take advantage of interchannel correlation and to
define common channel assignments (like stereo L/R, 5.1 surround, et
cetera). When encoding a large number of independent channels it is
expected that they are coded separately and if required, multiplexed
together in a suitable container like Ogg or Matroska."
Good info.
But this is a bit typical as an “answer”: HOW would you code many
channels separately in Flac (available sw to use etc.), and how to
multiplex into a “suitable container”?
Ok, no problem for anybody else... I am supposed to see! 😇
(https://xiph.org/flac/ogg_mapping.html
They don’t explain this at all, unless you take the faq answer as a
definition.)
Best,
Stefan
P.S.: They just have to extend (too) old definitions.
As Fons says, the limit is a limit (paraphrasing Theresa May) - and
not justified from a current perspective.
A few years ago I hacked the opusenc command line tool to encode
channels without inter-channel correlation, because the correlations in
the Opus codec were programmed for specific multi-channel schemes,
limited to 8 channels. The "joint stereo" MP3 mode is an example of such
a scheme, where channels are internally converted before encoding (see:
https://en.wikipedia.org/wiki/Joint_%28audio_engineering%29).The Opus
codec now have an Ambisonics mode with new inter-channel correlation
schemes. I don't know if the fine Xiph developers can "just" extend the
definitions of FLAC, if a special Ambisonics mode would be required, and
to what extent the 8-channel limit (as a limit) is a political issue.
For the multiplexing of multiple streams in a suitable container, it is
left as an exercise. And if the issue is just disk space, file
compression softwares (zip, gzip, etc) are still valid tools.

Marc
Post by Stefan Schreiber
Post by Fons Adriaensen
Post by Marc Lavallée
Easy to compile, support for FLAC, GPL3 license...
FLAC is supported for input only. The output is 9 channels,
 and FLAC can't handle that. Never understood why they put
 in that silly limit...
 Ciao,
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Stefan Schreiber
2018-07-29 21:56:11 UTC
Permalink
Post by Marc Lavallée
Post by Stefan Schreiber
 "FLAC supports from 1 to 8 channels per stream. Channels are
only grouped in FLAC to take advantage of interchannel correlation
and to define common channel assignments (like stereo L/R, 5.1
surround, et cetera). When encoding a large number of independent
channels it is expected that they are coded separately and if
required, multiplexed together in a suitable container like Ogg or
Matroska."
Good info.
But this is a bit typical as an “answer”: HOW would you code many
channels separately in Flac (available sw to use etc.), and how to
multiplex into a “suitable container”?
Ok, no problem for anybody else... I am supposed to see! 😇
(https://xiph.org/flac/ogg_mapping.html
They don’t explain this at all, unless you take the faq answer as
a definition.)
Best,
Stefan
P.S.: They just have to extend (too) old definitions.
As Fons says, the limit is a limit (paraphrasing Theresa May) -
and not justified from a current perspective.
A few years ago I hacked the opusenc command line tool to encode
channels without inter-channel correlation, because the correlations
in the Opus codec were programmed for specific multi-channel
schemes, limited to 8 channels. The "joint stereo" MP3 mode is an
example of such a scheme, where channels are internally converted
https://en.wikipedia.org/wiki/Joint_%28audio_engineering%29).The
Opus codec now have an Ambisonics mode with new inter-channel
correlation schemes. I don't know if the fine Xiph developers can
"just" extend the definitions of FLAC, if a special Ambisonics mode
would be required, and to what extent the 8-channel limit (as a
limit) is a political issue. For the multiplexing of multiple
streams in a suitable container, it is left as an exercise. And if
the issue is just disk space, file compression softwares (zip, gzip,
etc) are still valid tools.
Marc
- - - - -

1. I believe that the opus encoders/decoders have always supported
more than 8 channels.

2. The next question is what ogg channel mapping and consequently
real-world browsers allow...

But in some sense the hack you did is known. (More complicated is
maybe to make it work...)

3. If they already plan to issue some ogg ambisonics standard (using
ogg opus of course) since at least 2016: You also need an associated
mastering standard, which would not change or compress any audio data.
Correct?

So what is “political” about extending the channel count of FLAC?

Compromise proposal:

4. So let’s maybe use .wav or .caf for the “mastering format”.
Microsoft and Apple already allow more than 8 channels... 🤔

Best,

Stefan

P.S.: “Joint stereo” you could classify as parametric coding.
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Marc Lavallée
2018-07-29 22:29:05 UTC
Permalink
Post by Stefan Schreiber
1. I believe that the opus encoders/decoders have always supported
more than 8 channels.
Correct, but when encoding 8 or less channels, correlation is applied in
ways that are incompatible with Ambisonics; for example, the LFE channel
is filtered... With more than 8 channels, Opus don't correlate channels,
but it does now if the input stream is Ambisonics (and if the Ambisonics
mode, disabled by default, is compiled in).
Post by Stefan Schreiber
2. The next question is what ogg channel mapping and consequently
real-world browsers allow...
But in some sense the hack you did is known. (More complicated is
maybe to make it work...)
I tried only with 4 channels. It worked. I don't know if browsers are
now capable to support more than 8 channels. If the Octomic is getting
popular with VR content producers, maybe browsers will start supporting
streams with more than 8 channels (without systematically down-mixing
them to stereo).
Post by Stefan Schreiber
3. If they already plan to issue some ogg ambisonics standard (using
ogg opus of course) since at least 2016: You also need an associated
mastering standard, which would not change or compress any audio data.
Correct?
So what is “political” about extending the channel count of FLAC?
Multi-channel still mean Dolby 5.1 or 7.1. There's an inertia because
"standards" were designed as vendor lock-ins.
Post by Stefan Schreiber
4. So let’s maybe use .wav or .caf for the “mastering format”.
Microsoft and Apple already allow more than 8 channels... 🤔
Sure. Lossy codecs are not suited for mastering.
Post by Stefan Schreiber
P.S.: “Joint stereo” you could classify as parametric coding.
Ok.

Marc
Stefan Schreiber
2018-07-29 23:45:02 UTC
Permalink
Short comments (to text below):
(1)

The ambisonics input channels can’t be coded in some 7.1 (channel
coupling, LFE) style, agreed.

With opus you seem to need channel mapping #255, not #1 - the latter
 corresponds to (classical) 2D surround sound layouts.

(2) I believe that  FB is already using up to 11 channels coded with
opus, although I am not absolutely sure about. (Could say more about
this in a few weeks, hopefully.)

(3) Multi-channel != (classical) 5.1/7.1 surround sound.  In fact
surround sound is not a synonym for 5.1/7.1.

We are on the surround list, so should know about this!

But now we are getting slightly confused: Xipg.org’s Opus or Flac
don’t have to care about Dolby Digital or DD+ 5.1/7.1, right? So maybe
you mean 5.1/7.1 channel mapping?

To claim that 5.1 is “Dolby” doesn’t make sense. (There is an official
ITU layout standard, and many versions implemented/defined by DTS,
Mpeg, Sony and “anybody else”.)

https://www.itu.int/dms_pubrec/itu-r/rec/bs/R-REC-BS.775-3-201208-I!!PDF-E.pdf

So (righteously) you can implement 5.1 and 7.1 audio tracks since Vorbis...

(4) A lossless compression format could be used for mastering. I meant this.

Best,

Stefan

- - - - - - - 
Post by Marc Lavallée
Post by Stefan Schreiber
1. I believe that the opus encoders/decoders have always supported
more than 8 channels.
Correct, but when encoding 8 or less channels, correlation is
applied in ways that are incompatible with Ambisonics; for example,
the LFE channel is filtered... With more than 8 channels, Opus don't
correlate channels, but it does now if the input stream is
Ambisonics (and if the Ambisonics mode, disabled by default, is
compiled in).
Post by Stefan Schreiber
2. The next question is what ogg channel mapping and consequently
real-world browsers allow...
But in some sense the hack you did is known. (More complicated is
maybe to make it work...)
I tried only with 4 channels. It worked. I don't know if browsers
are now capable to support more than 8 channels. If the Octomic is
getting popular with VR content producers, maybe browsers will start
supporting streams with more than 8 channels (without systematically
down-mixing them to stereo).
Post by Stefan Schreiber
3. If they already plan to issue some ogg ambisonics standard
(using ogg opus of course) since at least 2016: You also need an
associated mastering standard, which would not change or compress
any audio data. Correct?
So what is “political” about extending the channel count of FLAC?
Multi-channel still mean Dolby 5.1 or 7.1. There's an inertia
because "standards" were designed as vendor lock-ins.
Post by Stefan Schreiber
4. So let’s maybe use .wav or .caf for the “mastering format”.
Microsoft and Apple already allow more than 8 channels... 🤔
Sure. Lossy codecs are not suited for mastering.
Post by Stefan Schreiber
P.S.: “Joint stereo” you could classify as parametric coding.
Ok.
Marc
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Aaron Heller
2018-07-30 00:19:12 UTC
Permalink
There's a IETF proposal from folks at Google for "Ambisonics in an Ogg Opus
Container", based on

Nachbar, et al., Ambix - A Suggested Ambisonics Format. 3rd International
Symposium on Ambisonics and Spherical Acoustics, Lexington, KY (2011)

and the idea of a default stereo decode from Etienne Deleflie's Universal
Ambisonic work



https://tools.ietf.org/html/draft-ietf-codec-ambisonics-07

Martin Leese has posted pointers to it here from time to time. Early
versions had errors, which I informed them of and were fixed in later
versions.


Aaron Heller (***@ai.sri.com)
Menlo Park, CA
Post by Stefan Schreiber
(1)
The ambisonics input channels can’t be coded in some 7.1 (channel
coupling, LFE) style, agreed.
Post by Stefan Schreiber
With opus you seem to need channel mapping #255, not #1 - the latter
corresponds to (classical) 2D surround sound layouts.
Post by Stefan Schreiber
(2) I believe that FB is already using up to 11 channels coded with
opus, although I am not absolutely sure about. (Could say more about this
in a few weeks, hopefully.)
Post by Stefan Schreiber
(3) Multi-channel != (classical) 5.1/7.1 surround sound. In fact
surround sound is not a synonym for 5.1/7.1.
Post by Stefan Schreiber
We are on the surround list, so should know about this!
But now we are getting slightly confused: Xipg.org’s Opus or Flac don’t
have to care about Dolby Digital or DD+ 5.1/7.1, right? So maybe you mean
5.1/7.1 channel mapping?
Post by Stefan Schreiber
To claim that 5.1 is “Dolby” doesn’t make sense. (There is an official
ITU layout standard, and many versions implemented/defined by DTS, Mpeg,
Sony and “anybody else”.)
https://www.itu.int/dms_pubrec/itu-r/rec/bs/R-REC-BS.775-3-201208-I!!PDF-E.pdf
Post by Stefan Schreiber
So (righteously) you can implement 5.1 and 7.1 audio tracks since Vorbis...
(4) A lossless compression format could be used for mastering. I meant this.
Best,
Stefan
- - - - - - -
Post by Marc Lavallée
1. I believe that the opus encoders/decoders have always supported more
than 8 channels.
Post by Stefan Schreiber
Post by Marc Lavallée
Correct, but when encoding 8 or less channels, correlation is applied in
ways that are incompatible with Ambisonics; for example, the LFE channel is
filtered... With more than 8 channels, Opus don't correlate channels, but
it does now if the input stream is Ambisonics (and if the Ambisonics mode,
disabled by default, is compiled in).
Post by Stefan Schreiber
Post by Marc Lavallée
2. The next question is what ogg channel mapping and consequently
real-world browsers allow...
Post by Stefan Schreiber
Post by Marc Lavallée
But in some sense the hack you did is known. (More complicated is
maybe to make it work...)
Post by Stefan Schreiber
Post by Marc Lavallée
I tried only with 4 channels. It worked. I don't know if browsers are
now capable to support more than 8 channels. If the Octomic is getting
popular with VR content producers, maybe browsers will start supporting
streams with more than 8 channels (without systematically down-mixing them
to stereo).
Post by Stefan Schreiber
Post by Marc Lavallée
3. If they already plan to issue some ogg ambisonics standard (using
ogg opus of course) since at least 2016: You also need an associated
mastering standard, which would not change or compress any audio data.
Correct?
Post by Stefan Schreiber
Post by Marc Lavallée
So what is “political” about extending the channel count of FLAC?
Multi-channel still mean Dolby 5.1 or 7.1. There's an inertia because
"standards" were designed as vendor lock-ins.
Post by Stefan Schreiber
Post by Marc Lavallée
4. So let’s maybe use .wav or .caf for the “mastering format”.
Microsoft and Apple already allow more than 8 channels...
Post by Stefan Schreiber
Post by Marc Lavallée
Sure. Lossy codecs are not suited for mastering.
P.S.: “Joint stereo” you could classify as parametric coding.
Ok.
Marc
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Martin Leese
2018-07-31 02:30:42 UTC
Permalink
Marc Lavall?e wrote:
...
Post by Marc Lavallée
I don't know if the fine Xiph developers can "just" extend the
definitions of FLAC, if a special Ambisonics mode would be required, and
to what extent the 8-channel limit (as a limit) is a political issue.
Extending a FLAC stream beyond eight
channels is not possible. There are two
problems; one simple, one less so:

The simple problem is that the field in the
header used for the number of channels is
only three bits.

Perhaps comparing FLAC with the Ogg
container and Vorbis codec will aid
understanding of the more difficult problem.

With Ogg, different streams can be either
chained (sequential) or grouped
(parallel/interleaved). Typically, metadata
streams would be chained (so they appear
before any audio data) and audio streams
would be grouped.

Within a single FLAC stream the audio is
split into blocks which are grouped. But within
each block the eight channels are chained.
This makes sense with a maximum of only
eight channels. Within a Vorbis stream the
audio is split into frames which are grouped.
However, because a Vorbis stream can
contain up to 256 channels, within each frame
the channels are also grouped.

So the maximum of eight channels is really
embedded into the FLAC standard. To change
this would require a whole new standard (or
the use of multiple grouped FLAC streams in
an Ogg container).

Regards,
Martin
--
Martin J Leese
E-mail: martin.leese stanfordalumni.org
Web: http://members.tripod.com/martin_leese/
Martin Leese
2018-08-02 16:37:07 UTC
Permalink
Post by Aaron Heller
There's a IETF proposal from folks at Google for "Ambisonics in an Ogg Opus
Container", based on
Nachbar, et al., Ambix - A Suggested Ambisonics Format. 3rd International
Symposium on Ambisonics and Spherical Acoustics, Lexington, KY (2011)
and the idea of a default stereo decode from Etienne Deleflie's Universal
Ambisonic work
I would instead recommend my proposal for a
stereo decode described at:
http://members.tripod.com/martin_leese/Audio/stereo_mix_proposal.html
http://members.tripod.com/martin_leese/Audio/StereoMix_chunk.html

This can be used not only in Ambisonic files
(see Example 3 on the Stereo Mix chunk page),
but also in non-Ambisonic multi-channel files.
This makes it more likely to be adopted.

Regards,
Martin
--
Martin J Leese
E-mail: martin.leese stanfordalumni.org
Web: http://members.tripod.com/martin_leese/
Marc Lavallée
2018-08-02 17:21:29 UTC
Permalink
I changed the subject.

Martin, I like your proposal because the chunks in WAV files (as
metadata in source files), could be transferred to transcoded files an
used by players (for example by web browsers). That would enable the
distribution of multi-channel streams in their native format
(Ambisonics, Quad, 5.1, 7.1), with stereo compatibility.

In the IETF proposal , there's also the idea of including an optional
non-diegetic stereo track (or stream); I'm not aware of any format with
a similar feature (as part of the format specification).

Marc
Post by Martin Leese
Post by Aaron Heller
There's a IETF proposal from folks at Google for "Ambisonics in an Ogg Opus
Container", based on
Nachbar, et al., Ambix - A Suggested Ambisonics Format. 3rd International
Symposium on Ambisonics and Spherical Acoustics, Lexington, KY (2011)
and the idea of a default stereo decode from Etienne Deleflie's Universal
Ambisonic work
I would instead recommend my proposal for a
http://members.tripod.com/martin_leese/Audio/stereo_mix_proposal.html
http://members.tripod.com/martin_leese/Audio/StereoMix_chunk.html
This can be used not only in Ambisonic files
(see Example 3 on the Stereo Mix chunk page),
but also in non-Ambisonic multi-channel files.
This makes it more likely to be adopted.
Regards,
Martin
Stefan Schreiber
2018-08-02 18:07:30 UTC
Permalink
Post by Marc Lavallée
I changed the subject.
Martin, I like your proposal because the chunks in WAV files (as
metadata in source files), could be transferred to transcoded files
an used by players (for example by web browsers). That would enable
the distribution of multi-channel streams in their native format
(Ambisonics, Quad, 5.1, 7.1), with stereo compatibility.
In the IETF proposal , there's also the idea of including an
optional non-diegetic stereo track (or stream); I'm not aware of any
format with a similar feature (as part of the format specification).
- - - - 

The idea was possibly adopted from the .TBE format (10 channels),
although Facebook supports Ambix-9 + 2 (11 channels) as well. (By now.)

But be aware that non-diegetic stereo is not a multichannel downmix:
It is a second audio stream, usually used as comment or background
(music) track. 

Best,

Stefan

- - - - -
Post by Marc Lavallée
Marc
Post by Martin Leese
Post by Aaron Heller
There's a IETF proposal from folks at Google for "Ambisonics in an Ogg Opus
Container", based on
  Nachbar, et al., Ambix - A Suggested Ambisonics Format. 3rd
International
Symposium on Ambisonics and Spherical Acoustics, Lexington, KY (2011)
and the idea of a default stereo decode from Etienne Deleflie's Universal
Ambisonic work
I would instead recommend my proposal for a
http://members.tripod.com/martin_leese/Audio/stereo_mix_proposal.html
http://members.tripod.com/martin_leese/Audio/StereoMix_chunk.html
This can be used not only in Ambisonic files
(see Example 3 on the Stereo Mix chunk page),
but also in non-Ambisonic multi-channel files.
This makes it more likely to be adopted.
Regards,
Martin
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