Coded data generation or conversion – Analog to or from digital conversion – Nonlinear
Patent
1996-09-12
1998-11-24
Young, Brian K.
Coded data generation or conversion
Analog to or from digital conversion
Nonlinear
H03M 118
Patent
active
058413855
ABSTRACT:
A system which performs automatic gain control on received audio data. The system comprises an analog adjustable gain amplifier coupled to a digital gain control loop which is preferably a digital signal processor, with an A/D converter and D/A converter interposed between the amplifier and control loop. The invention thus advantageously amplifies the analog input signal before being converted into a digital signal. This results in better performance than prior art system which amplify an already converted to digital signal which may have already been clipped before the signal could be attenuated. The combined digital/analog method provides improved detection of silence to avoid amplifying background noise. The gain control loop comprises a long-term energy averager and gain calculator as well as a short-term energy averager and gain calculator which receive the digital audio output signal. The gain calculators periodically generate gain adjustment outputs based on the average energy of the audio signal so as to attenuate or amplify the analog audio input signal. Thus the invention advantageously achieves the apparently conflicting objectives of having an automatic gain control system which is both stable and responds quickly to clipping. The gain control loop further comprises a voice activity detector which detects the presence of silence versus voice activity based on ratios of the long-term and short-term energy averages. The long-term energy averager advantageously pauses operation during silence. Additionally, the gain control system amplifies the audio input signal only during the voice activity thus suppressing noise amplification during periods of silence.
REFERENCES:
patent: 4611342 (1986-09-01), Miller et al.
patent: 5016205 (1991-05-01), Shumway
patent: 5630221 (1997-05-01), Birleson
patent: 5631969 (1997-05-01), Hanson
D. Morgan, A/D Conversion Using Geometric Feedback AGC, IEEE Transactions on Computers, vol. C-24, No. 11, Nov. 1975.
McGraw-Hill Encyclopedia of Science & Technology, 1982 by McGraw-Hill, Inc., pp. 881-882.
Advanced Micro Devices , Inc.
Davis E. Alan
Hood Jeffrey C.
Young Brian K.
LandOfFree
System and method for performing combined digital/analog automat does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with System and method for performing combined digital/analog automat, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and System and method for performing combined digital/analog automat will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1707933