Audio automatic gain control system
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United States of America Patent
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Nov 9, 1999
Grant Date -
N/A
app pub date -
Jul 7, 1997
filing date -
Jul 7, 1997
priority date (Note) -
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Abstract
An automatic gain control (AGC) algorithm is provided to the digital signal processor instructions of an audio processing unit of a multimedia multipoint server. The AGC algorithm operates to bring the power level of the audio signal of every active channel to within a fixed range. The AGC algorithm allows the use of non-calibrated microphones, corrects for long distance signal attenuation, and provides improved audio level reference for audio switching and audio level video switching. The AGC algorithm is structured into two steps: calibration and gain control. The calibration includes defining a noise threshold. Gain control includes first calculating a dynamic speech detection level. Second, with reference to the speech detection level, determining whether an incoming audio signal is a speech-based audio signal. Finally, when the audio signal is determined to be of speech, calculating a smoothed power estimation of the speech signal, and appropriately updating the gain on each channel so that the power level of the speech signal is moved toward or confined within the fixed experimental range.
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