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How To Connect A Google+ Hangout-On-Air To a Conference Bridge: Part 1 – Background

Interconnecting A Google Hangout & ZipDXThe VoIP Users Conference is closing upon 500 weekly sessions, each one more-or-less a conference call. Along the way the manner in which the calls happen has evolved. A bit of background about this will serve to frame why I’ve been seeking a way to interconnect a Google+ Hangout and the ZipDX conference bridge.

Those five hundred calls break down into three broad categories;

Talkshoe: 3/2007 – 1/2009

Talkshow-Polycom-IP650Randy Resnick started the VUC using the Talkshoe conference service. Talkshoe was and is a conference service built for podcasters. It allows connection by traditional telephone call. It is, in the finest of PSTN traditions, a narrowband service. It’s most significant forward-looking feature is that it allows connection via SIP URI. That allows users to connect for free from anywhere in the world with internet access.

ZipDX: 1/2009 – Present


In November 2008 I coordinated a VUC call on the topic of HDVoice. That call featured David frankel, CEO of ZipDX, the leading HDVoice-capable conference service. David was gracious enough to provide a handful of licenses to Counterpath’s Eyebeam soft phone ensuring that a dozen participants could experience HDVoice for themselves. On that occasion we cross-connected Talkshoe to ZipDX.

In that case, connecting the two bridges was easily accomplished using a Polycom SoundPoint IP650 desk phone. It could reach ZipDX via SIP URI and Talkshoe via the PSTN. It could perform an on-phone conference, and even make a local recording of the call to a USB memory stick.

The call with ZipDX went very well. So well that by January 2009 ZipDX had stepped up to sponsor the VUC, offering their conference service as the primary host platform. This week marks five years of VUC calls on ZipDX.

Hangout + ZipDX: 7/2011 – Present

VUC is ever-evolving. When Google+ began offering their Hangout video conference service in 2011 Randy added that to the mix. However, a Hangout has a limited number of seats. Given a larger live audience than a Hangout can support, that meant cross-connecting it to the ZipDX conference bridge.

Google giveth and Google taketh-away. Hangout’s-On-Air are a very nice extension to the toolset provided by a Hangout. The call can now be presented as a live You Tube stream and automatically recorded for later use as a You Tube video. So end-eth the example of where Google giveth.

Unfortunately, Google has also eliminated our ability to interconnect with the Hangout. No interop via the PSTN. No interop via SIP. No interop via XMPP.

This even as we were truly working out how to best use the visual aspect of the tool. Regrettably, the Hangout-On-Air had become an island.

A Google Hangout Is An Island

We still have the requirement to support an audience that connects using a variety of pathways. The audience can engage via the PSTN. ZiPDX provides US PSTN dial-in and connection via SIP URI, supporting the wonderful HDVoice that drew us to ZipDX in the first place.

Voxbone provides local dial-in numbers in over 50 countries. There’s also a streaming MP3 feed and a streaming YouTube feed, although these feeds are not interactive.

While the visual tool set provided by a Hangout is useful, maintaining an engaged global audience means connecting to various telephonic avenues. The Hangout alone would not suffice if we wanted to sustain the existing live audience in all it’s various forms and locations.

Randy’s Solution

For quite some time Randy handled the complexities of interconnecting the Hangout and ZipDX at his location in Bordeaux, France. His background as a musician provided some specific insight into how it could be done. He uses a small audio mixer with two aux sends to create a pair of mix-minus feeds, one for each service.  In so doing he is essentially the pivot point around which the services are connected.

Randy's Way

While the setup can be daunting to manage on a live call, it works very well. So well that there was no need for a different solution.

However, in recent weeks there have been times when Randy’s ISP has been a problem. His DSL service has been suffering intermittent problems. Given the usual arrangement, when his connectivity drops the connection between the Hangout and ZipDX is also lost.

The guest(s) to be interviewed are typically on the Hangout with a handful of VUC regulars. The rest of the audience is on ZipDX. When the services are separated most of the audience drops into silence. Not good.

An Initial Hack: Hardware Intensive

It occurred to me that a Hangout is basically a soft phone, and I could connect to ZipDX using another soft phone. If that was the case then it would be just a simple matter of cross-connecting the audio from the two clients.

The simplest possible case was to connect a pair of utility PCs that I had on-hand. By using desktops I could take advantage of the line-level analog audio in & out. That would avoid the noise and level problems likely to happen when connecting a line-level output to a microphone level input.

I tried this arrangement for a VUC call #450 with Marc Abrams of Mocet in August 2013. I used Chrome on the more powerful PC to connect to the Hangout. It was wired to an older PC running Blink connected to ZipDX.

This setup worked reasonably well for an experiment, but was not ideal. There was some 60 Hz hum in the audio feed to ZipDX. This was the result of electrically interconnecting the two computers. I could find no way to eliminate the hum quickly or easily that day.

Also, audio level control was a bit on the complicated side. Each computer had audio levels controls at the OS and application level. It was tricky ensuring the appropriate level on both services.

A Better Way

There simply had to be a better way. Happily, with some persistence,  I can say that we have found it! I’ll describe how we have bridged the two services for the most recent VUC calls in part two of this little series.

This Post Has 2 Comments
  1. Excellent article as usual. Small typo I believe… “So well that by January 2008 ZipDX…” should be 2009?

    While the on air hangouts do not allow PSTN connections, do the normal hangouts still allow such cross connection? (Albeit without the live Youtube stream).

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