The benefit of doing this is questionable, but could work well in some rooms. Some designers put microphone signals in their own AEC references to try to improve gain-before-feedback in voice-lift systems. The AEC will converge to a signal path with no echo in it and must re-converge when a far-end signal (that belongs in the AEC reference) becomes active. If a signal is sent to the AEC reference, but not played out of the loudspeaker, the AEC could diverge whenever the signal is active.When the signal is active, there will be no corresponding audio detected by the microphone. One exception to this is in the case of positional audio, described below. In most cases, it is preferable to include program audio in the AEC reference. This is less severe than echo from the far-end, but still not ideal. If program audio is missing from the reference, the far-end may hear a muddy or reverberant version of the program audio (including the direct mix of program audio sent to the far-end, along with what is picked up locally by the mics). This is a common pitfall that the CRR prevents.
If a matrix cross-point between a far-end input and the AEC reference is mistakenly muted, echo will be heard from that far-end, but the problem will not be noticeable in the local room. If a signal is not in the AEC reference, the AEC will not cancel it. Furthermore, all the loudspeakers in the room should play that same mix. In general, the AEC reference should receive a mix of all the far-end and program audio that will be played through the loudspeakers. The Reference Must Contain the Correct Signals However, there are often questions about how processing outside the CRR affects the AEC reference, and there may be designs that use AEC without using the CRR.īelow are some principles of the use of the AEC reference in good conference room designs and some advice about common applications. The Conference Room Router (CRR) goes a long way to ensure the AEC reference is done correctly. It is also one of the most challenging aspects of conference room design. Correct routing and processing of the Acoustic Echo Cancellation (AEC) reference is critical for preventing echo in conference rooms.
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