Microphone acoustic echo cancellation software

Far-end audio is almost always mono, and far-end audio is our primary concern for AEC.Дialog-heavy program audio is also likely to have most of its energy panned to the center, and would be canceled even with a mono AEC reference. Except for highly customized telepresence rooms, microphones are rarely panned even when sent to stereo codecs. In practice, an AEC with a mono reference will work well most of the time in a stereo conference room. An AEC with a stereo reference is designed to handle this properly, while a mono AEC is not. The echo path between the left and right loudspeakers and the microphone have different impulse responses, and a mono AEC cannot converge to both at the same time. If the stereo signal has much separation, significantly different signals will be played from the left and right loudspeakers. Stereo signals in a mono AEC reference are theoretically a problem. This provides the lowest latency for local reinforcement and will cause no problems with the AEC. In most cases, it is preferable to use pre-AEC microphone signals for voice-lift and to leave the microphones out of the AEC references. In other cases, the feedback reduction behavior of the AEC could be inconsistent, or residual echo could be audible by the far-end during double-talk. 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.Д«elow 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.

Microphone acoustic echo cancellation software