【 Weak current College 】 video conferencing in the discovery and eliminating acoustic echo

ECHO is a TV in the most common sound problems. At the meeting of the TV system debugging, remove echo of discovery and require system maintenance personnel to focus on one topic.
First, the definition and characteristics of ECHO
1. What is the echoes of videoconferencing
In television, when the sound signal of the venue to the other site, move to the other side of the microphone, mixer, videoconference systems, and other audio devices, and then back to the venue, the lead in this venue to hear their own voices, after delay of this sound is called a meeting of the echo of the TV.
2. characteristics of ECHO
(1) echo and compared their own voices, there is a noticeable delay.
For example: when a person is in a valley on a mountain wall say a Word, you will hear the echo of their clear, and you may not hear it again, like the mountain it was learning to speak to you. When you are in a empty big house speaks, is also very easy to hear the echoes of their own, but this echo may only heard in the last few words, and incomplete, if it is continuous and faster speech, you'll find this echo interference will make people around did not catch you said.
Videoconference system echo principle and produced by the same, just the path to spread a little difference. Figure 1 is a TV meeting echoes propagation path diagram.
(2) echo is generally lower than that of their own voice.
For the echo of which spreads through the air, as energy consumption, ECHO than sound source voice to small; for video conference system, although it also converts the sound power, normally echo smaller. Unless human mistake operation, through the sound mixer, audio equipment for signal gain, will have a larger echo.
(3) the size of the ECHO and the size of the sound source, the mode of transmission and the surrounding environment.
If the speaker's voice is small, it is difficult to produce echo, or echo effects can be ignored; in an empty House and a narrow room speech will feel different; whereas the same House, and did not place any thing and put a lot of tables and chairs, as well as the walls, floor and furniture for acoustical materials, spoke of feeling.
2. how to eliminate the echo of the TV Conference
1. echo cancellation and echo suppression
Echo cancellation, through ECHO path analysis, estimation of their characteristics, utilization of echo path parameter structure simulation of ECHO channel, analog echo generation process, the resulting analog echo signal and reception will be eliminated by inverse sum received signal of ECHO. Acoustic echo suppression is a voice channel capacity to eliminate acoustic echo.
2. echo cancellation and echo suppression of
General for videoconferencing products, will adopt some echo cancellation mechanism, or use advanced adaptive algorithm for intelligent adjustment parameters to ensure that the venue of the best sound effects. In Anhui Province meeting network of Huawei VP8000 conference system, for example, the system is designed to use the built-in echo cancellation. And external acoustic echo canceller, built-in acoustic echo canceller with no user installation, adjustment, easy virtues.