My scope of interests spans both surround sound and IP telephony. It seems that
there is finally starting to be some convergence between these spheres.
For example, several companies have recently launched "3D" audio conferencing
services for business. Dolby Voice is offered by BT Conferencing. Voxeet offers
a purely software based approach.
Of course, these are not actually 3D audio as they proclaim. They lack any
conception of height, making them at best some sort of planar surround. It may
be most appropriate to refer to them as binaural conferencing.
Freeswitch is one of the leading open source telecom switching projects. They
recently launched a project they call "Verto". It's a binaural conferencing
engine that build upon prior implementation of WebRTC and the Opus audio codec.
You can reach it by pointing the Chrome web browser at
https://webrtc.freeswitch.org/
I was on one of the very first public calls where Verto was used. Some
participants were connected via the web. Those people participated in stereo,
hearing the various participants arrayed around their sound stage. Those people
generally liked what they heard. There were no technical issues with the sound.
Others connected using more traditional mono end-points, including hardware IP
phones, cell phones, or soft phones on computers. These people often didn't
like what they heard. For them the mono sum of the stereo soundstage was a
jumble, most typically with poor control of levels.
I joined by way of a Polycom VVX-600, which is a high-quality, albeit mono, IP
phone. I was connected over G.722.1C, so I had a 14 KHz usable audio path. To
my ear some participants sounded a lot lower in volume and also with the high
frequencies dramatically rolled off. It sounded a lot like problematic use of
an old "vocal eliminator" tool.
I am not a software developer, nor was I prepared to question the dev team on
the call about the specifics of their spatial manipulations. Given
unsatisfactory results for many, on that first call they simply disabled the
spatial trickery so that the call could continue in a productive manner.
However, I thought that I might ask this group if Ambisonics, in one fashion or
another, would be helpful in allowing such a project to preserve a coherent
mono down-mix for those participants to join a call using traditional means?
The alternative may be to hold separate, parallel conferences; mono & binaural.
This would be transparent to the end-users, but may be more resource intensive
fort the host hardware. Perhaps also more difficult to manage.
Michael Graves
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