Other Video Codecs; Connecting The Inputs And Outputs; Setting The Aec Reference - Polycom Vortex EF2241 Application Note

Other Video Codecs

C
ONNECTING THE
In order to send and receive audio to the video codec, you need to observe the following procedure:
1. Connect one of the Outputs of the Vortex device to the Input of the codec. By default, Outputs A-C
of the Vortex device are mix-minus versions of the Inputs A-C signals.
2. Connect the line level output of the codec to one of the line level inputs of the Vortex device (Inputs
A-D). You may use one of the Mic/Line level inputs, but you need to disable all processing on that
input (AEC, AGC, NC, Automixer), disable Phantom Power, and set the input to line level versus the
default of mic level.
On some codecs, you must use a specific combination of Inputs or Outputs so that the
incoming audio signal is not echo cancelled and/or not sent to a specific output. Please
follow our instructions for using the appropriate combination of Inputs and Outputs.
Please follow our instructions for wiring the Vortex device to the codec. Failure to do so
may induce noise into the signals sent and received from the codec.
3. Raise the gain on the appropriate Input of the Vortex device to +10 dB.
4. Lower the gain on the appropriate Output of the Vortex device to -10 dB.
5. Go to A
S
UDIO ETTINGS
6. Go to A
S
UDIO ETTINGS
It is important to set the gain structure correctly so that you don't clip the input audio
stage of the codec and that the Vortex device gets a good signal to perform processing
with. The nominal input and output of the codec is .3 V rms (at 0 dB of gain on both inputs
and outputs). The nominal input and output of the Vortex device is .775 V rms. This
equates to a difference of 8.24 dB between the two nominal levels. For simplicity, you
may round that value to 10 dB.
S
ETTING THE
Some video codecs require the use a specific combination of Input and Output connections to avoid creating
an audio loop-back inside the codec. For these codecs, we recommend the following:
I
NPUTS AND
, I , L S
NPUT EVEL ETTINGS
, O , L S
UTPUT EVEL ETTINGS
AEC R
EFERENCE
O
UTPUTS
and set the gain on the proper Input to 0 dB.
and set the gain on the proper Input to 0 dB.
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