[opus] opusenc for ambisonics?

[Emily Bowman]

Unfortunately, ambisonics aren't exposed in opusenc yet, thus the trouble.
They're an API-only feature, but it's a good time to discuss what such a
command-line interface would look like, notably: how to specify multiple
streams & stream order, select the mapping family, coupled channels, and
how to specify the matrix (for family 3). Likewise, there's no multistream
support at the moment, so two birds might be felled with one push. I have
ideas, but I've never used ambisonics and really don't know what the use
case would look like.

On Wed, Dec 18, 2019 at 10:00 AM Marc Lavallée <marc at hacklava.net> wrote:

> Le 19-12-18 à 12 h 29, Marc Lavallée a écrit :
>
> Hi Andrew,
>
> I suspect that the configure option should be enable-ambisonics (instead
> of enable_ambisonics), but for each of opus, libopusenc, opusfile and
> opus-tools git repos (on master branch), when I try "./configure
> --enable-ambisonics", I get this error message:
>
> configure: WARNING: unrecognized options: --enable-ambisonics
>
> I found that the --enable-ambisonics options is in opus 1.1.3, but no
> longer in 1.3 versions; starting with version 1.3-rc2, support for
> ambisonics is enabled by default, but I don't know how to use it.
>
> I recompiled everything using opus 1.1.3 with the --enable-ambisonics
> option, but opusenc don't offer an option for mapping families.
>
> It's all very confusing.
>
> Thanks for your help.
>
> Marc
> Le 19-12-18 à 11 h 52, Andrew Allen a écrit :
>
> Hi Marc,
>
> In order to use the ambisonics API, if you haven't already, you will need
> to activate the enable_ambisonics build flag during configuration.
> Then, when encoding the file, make sure to manually select mapping family
> 3 since opus does not auto-detect ambisonic files.
>
> Let me know if you have any questions!
>
> Cheers,
> Andrew
>
> On Tue, Dec 17, 2019 at 7:16 PM Marc Lavallée <marc at hacklava.net> wrote:
>
>> I compiled the latest (git master) of opus, libopusenc, opusfile and
>> opus-tools:
>>
>> $ opusenc --version
>> opusenc opus-tools 0.2-8-g4976421 (using libopus 1.3.1-4-gad8fe90d)
>>
>> I tried to encode a 3rd order Ambisonics wav file with the standard
>> Ambix (ACN-SN3D) format; opusinfo is reporting :
>>
>> Streams: 16, Coupled: 0
>>     Channel Mapping Family: 255 Map: [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10,
>> 11, 12, 13, 14, 15]
>>
>> How to encode the file so that the Mapping Family is 3, as suggested
>> here ? : https://people.xiph.org/~jm/opus/opus-1.3/
>>
>> Marc
>>
>>
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