System and method for performing automatic gain control with gain scheduling and adjustment at zero crossings for reducing distortion

Claim 1

A system which performs automatic gain control on received audio data, comprising: an amplifier with an adjustable gain which receives an audio input signal and a gain input and generates an audio output signal, wherein said amplifier selectively adjusts the gain of said audio output signal according to said gain input; and a gain control loop coupled to said amplifier which receives said amplified audio output signal and generates a gain output signal provided to said gain input of said amplifier to selectively adjust said gain of said amplifier, wherein said gain control loop further generates a gain adjustment signal, wherein said gain control loop comprises: a zero-crossing detector which receives said audio output signal and generates a zero crossing output upon detection of a zero crossing, wherein said zero crossing occurs when a product of two consecutive samples of said audio output signal being less than or equal to zero; a gain adjustment scheduler which receives said zero crossing output and said gain adjustment signal, wherein said gain adjustment scheduler maintains a previous gain output signal value, wherein said gain adjustment scheduler calculates a number of gain adjustment steps by dividing said gain adjustment signal by a gain step, wherein for each of said number of gain adjustment steps said gain adjustment scheduler waits a gain adjustment interval then generates said gain output signal when said zero crossing output indicates an occurrence of said zero crossing, wherein said gain output signal has a value which is one said gain step different than said previous gain output signal value.

Claim 2

A system which performs automatic gain control on received audio data, comprising: an amplifier with an adjustable gain which receives an audio input signal and a gain input and generates an audio output signal, wherein said amplifier selectively adjusts the gain of said audio output signal according to said gain input; and a gain control loop coupled to said amplifier which receives said amplified audio output signal and generates a gain output signal provided to said gain input of said amplifier to selectively adjust said gain of said amplifier, wherein said gain control loop further generates a gain adjustment signal, wherein said gain control loop comprises: a zero-crossing detector which receives said audio output signal and generates a zero crossing output upon detection of a zero crossing, wherein said zero crossing occurs when a product of two consecutive samples of said audio output signal being less than or equal to zero; a gain adjustment scheduler which receives said zero crossing output and said gain adjustment signal, wherein said gain adjustment scheduler maintains a previous gain output signal value, wherein said gain adjustment scheduler calculates a number of gain adjustment steps by dividing said gain adjustment signal by a gain step, wherein for each of said number of gain adjustment steps said gain adjustment scheduler waits a gain adjustment interval then generates said gain output signal when said zero crossing output indicates an occurrence of said zero crossing, wherein said gain output signal has a value which is one said gain step different than said previous gain output signal value.

Claim 6

A system which performs automatic gain control on received audio data, comprising: an amplifier with an adjustable gain which receives an audio input signal and a gain input and generates an audio output signal, wherein said amplifier selectively adjusts the gain of said audio output signal according to said gain input; and a gain control loop coupled to said amplifier which receives said amplified audio output signal and generates a gain output signal provided to said gain input of said amplifier to selectively adjust said gain of said amplifier, wherein said gain control loop comprises: a long-term energy averager which receives said audio output signal and calculates a long-term energy average of said audio output signal based on a first number of samples of said audio output signal, wherein said long-term energy averager generates a long-term energy average output in response to said calculated long-term energy average; a short-term energy averager which receives said audio output signal and calculates a short-term energy average of said audio output signal based on a second number of samples of said audio output signal, wherein said short-term energy averager generates a short-term energy average output in response to said calculated short-term energy average, wherein said second number is less than said first number; and a voice activity detector which receives said long-term energy average output and said short-term energy average output to detect substantial voice activity, wherein said automatic gain control system amplifies said audio input signal only during said substantial voice activity.

Claim 7

A system which performs automatic gain control on received audio data, comprising: an amplifier with an adjustable gain which receives an audio input signal and a gain input and generates an audio output signal, wherein said amplifier selectively adjusts the gain of said audio output signal according to said gain input; and a gain control loop coupled to said amplifier which receives said amplified audio output signal and generates a gain output signal provided to said gain input of said amplifier to selectively adjust said gain of said amplifier, wherein said gain control loop comprises: a long-term energy averager which receives said audio output signal and calculates a long-term energy average of said audio output signal based on a first number of samples of said audio output signal, wherein said long-term energy averager generates a long-term energy average output in response to said calculated long-term energy average; a short-term energy averager which receives said audio output signal and calculates a short-term energy average of said audio output signal based on a second number of samples of said audio output signal, wherein said short-term energy averager generates a short-term energy average output in response to said calculated short-term energy average, wherein said second number is less than said first number; and a voice activity detector which receives said long-term energy average output and said short-term energy average output to detect substantial voice activity, wherein said automatic gain control system amplifies said audio input signal only during said substantial voice activity.

Claim 10

A method for performing automatic gain control on a received audio input signal, comprising: receiving a gain input signal; amplifying said audio input signal to generate an audio output signal according to said gain input signal; detecting a zero crossing of said audio output signal; calculating a number of gain adjustment steps by dividing a gain adjustment signal by a gain step; for each of said number of gain adjustment steps waiting a gain adjustment interval, generating a gain output: signal, and providing said gain output signal to said gain input signal.

Claim 11

A method for performing automatic gain control on a received audio input signal, comprising: receiving a gain input signal; amplifying said audio input signal to generate an audio output signal according to said gain input signal; detecting a zero crossing of said audio output signal; calculating a number of gain adjustment steps by dividing a gain adjustment signal by a gain step; for each of said number of gain adjustment steps waiting a gain adjustment interval, generating a gain output: signal, and providing said gain output signal to said gain input signal.

Claim 15

A method for performing automatic gain control on a received audio input signal, comprising: receiving a gain input signal; amplifying said audio input signal to generate an audio output signal according to said gain input signal; calculating a long-term energy average of said audio output signal based on a first number of samples of said audio output signal; calculating a short-term energy average of said audio output signal based on a second number of samples of said audio output signal; detecting substantial voice activity on said audio output signal; said amplifying said audio input signal only during detection of said substantial voice activity.

Claim 16

A method for performing automatic gain control on a received audio input signal, comprising: receiving a gain input signal; amplifying said audio input signal to generate an audio output signal according to said gain input signal; calculating a long-term energy average of said audio output signal based on a first number of samples of said audio output signal; calculating a short-term energy average of said audio output signal based on a second number of samples of said audio output signal; detecting substantial voice activity on said audio output signal; said amplifying said audio input signal only during detection of said substantial voice activity.