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Design Guide for the Polycom SoundStructure C16, C12, C8, and SR12
2 - 16
In order for the local acoustic echo canceller to cancel the acoustic echo of the
remote participants, it must have an echo canceller reference defined. The echo
canceller reference includes all the signals from the remote site that should be
echo cancelled. In the following figure, the AEC reference for both the local
and remote rooms includes the audio that is played out the loudspeaker. See
Appendix B - Designing Audio Conferencing Systems for additional
information on audio conferencing systems and acoustic echo cancellation.
Within SoundStructure devices, the acoustic echo canceller on each input can
have either one or two AEC references specified per input signal. For
traditional monaural audio or video conferencing applications, only one
acoustic echo canceller reference is used and that would typically be the signal
that is sent to the single loudspeaker zone. See the “8 microphones, video, and
telephony application” in Chapter 9 for an example.
Applications that have two independent audio sources played into the room
such as stereo audio from a stereo video codec require two mono AEC
references, or one stereo AEC reference. See the 8 microphones and stereo
video conferencing application in Chapter 9.
An acoustic echo canceller reference can be created from any output signal or
any submix signal. For a SoundStructure C16 device this means that there are
32 possible echo canceller references (16 outputs + 16 submixes) that can be
defined and selected.
SoundStructure SR-Series Products
The SoundStructure SR12 has a similar architecture to the SoundStructure
C-series. While the SoundStructure SR12 does not include acoustic echo
cancellation processing it does include noise cancellation, automatic
microphone mixing, matrix mixing, equalization, feedback elimination,
dynamics processing, delay, and submix processing. The “SR” in the name
stands for 'sound reinforcement'.
The SoundStructure SR12 is designed for both the non-conferencing
applications where local audio is played into the local room or distributed
throughout a facility and for conferencing applications to provide additional
line input and output signals when linked to a C-series product. Applications
for the SoundStructure SR12 include live sound, presentation audio, sound