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C20 microphone audio signal

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Feb 12th, 2014
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Hi Folks,

I've seen posts about using the C20's microphone in other scenarios, so then discussions about pinouts and balanced to unbalanced coverters, etc -- but I'm wondering if there is a simpler way (perhaps built in way) to get what I'm looking for.

My older polycom unit had VCR output, so that I could record a videoconference locally -- this was handy so that I could take the audio and video signals (which included the local mic signal) and dump them into a capture card (and utilize the camera and mic for webinars, etc).

Is there a way to accomplish the same thing with a C20?  Getting the video hasn't been too difficult, but the microphone audio seems to be the challenge. I don't see any way in the config to output locally the mic signal (which makes sense).  My only route may be splitting off the mic connection (making necessary Y adapters, converters, etc)?  Other thoughts?

Thank you for any help.


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Overall Rating: 4 (1 ratings)
Martin Koch Sun, 02/16/2014 - 15:44
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Without "hacking" I do not see that there is an official way to support this on the C20.

The C20 is a basic system, what you are trying to archive is in the league of the C40 or better C60/C90 where you have

integrator incl. audio mixer capabilities.

You could also use an infrastructure based recording, like MCU+TCS.

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carlton.snodgrass Wed, 02/19/2014 - 05:33
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Thank you, Martin... very helpful as you saved me research time.

If anyone has experience with a hack that accomplishes my goal, I'd love to hear it!


Steve Kapinos Wed, 02/19/2014 - 15:53
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You'd have to use an external mixer.  The C20 does not provide an output with that mix type.

Wayne DeNardi Wed, 02/19/2014 - 17:14
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Hi Carol,

You'd need to conenct the microphone(s) to an external mixer, then take the outputs from this mixer to both your SX20 and your recorder.  Given that the video may be delayed slightly from the SX20 to the recorder, you may need to introduce some delay in the local audio feed too.

Something like this:


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