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LADSPA Integrated Into FreeSWITCH

For me one of the great frustrations of conference bridges is that they don’t give you the kind of control of audio properties that is commonly found in even simple audio mixing and editing suites. Wideband conference services, like ZipDX, make the conference experience a lot better, but there’s a lot of room for improvement.

Of course, this comes from the perspective of someone who has spent their working life in audio/video production, and only came to voip & podcasting later in life. Yes, a veritable Michael-come-lately. I bring to projects like the VUC the expectation of control that simply isn’t commonly possible. However, that is changing and we can thank the Freeswitch dev team for taking a leadership role in crossing these worlds.

Which brings me to the headline worth noting; Michael Collins this week posted on the Freeswitch site a notice that they have created a module called mod_ladspa that lets Freeswitch users leverage the Linux Audio Developer’s Simple Plugin API. This lets Freeswitch users intercept the audio streams involved in calls and process them using any of a considerable library of plug-ins.

Browsing the list of LADSPA plug-ins I see some useful things like equalization (frequency response contouring) and level control. I think that a compressor/limiter plug-in could be tremendously useful in matching audio levels for a conference bridge. An adjustable audio gate would also be handy when dealing with someone in a noisy room who doesn’t self-mute.

There are a lot of plug-in that create effects, these might be useful if someone wanted to disguise their voice. Others create reverberation or delay resulting in spatial effects.

In many cases, various aspects of these processes I describe have been built into commercial conference bridges or telco line interfaces for broadcasters. The trouble is that these are often black boxes to the end-user, fully automatic, with no adjustable properties. That limits their utility as a part of a creative process.

The availability of such real-time processing, combined with newer wideband, low-latency codecs, create a very interesting audio canvas. It brings voip-space closer to a proper music production toolset. I think that I will soon be building a Freeswitch system so that I can experiment with this new capability.

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