Controlling attenuation during echo suppression
AssigneeFreescale Semiconductor, Inc.
InventorsDavid L. Barron, William C. Yip, Sean S. You
Life of this patent
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Abstract
An echo canceling system receives and transmits audio signals between a far end and a near end. During single talk, which is when only one end is originating audio, the path back to the originator is impeded by echo cancellation and attenuation. When there is double talk, which is when both ends are originating audio, the attenuation is removed, or at least significantly reduced. This is achieved by using ERLE, which itself is a known signal used for other purposes in an echo cancellation system, to provide information as to when double talking is occurring. This allows for stopping the attenuation for the double talk situation, which is the desired result.
Claims36
A method comprising:
- filtering a far end signal to produce an estimate of an echo in a near end signal;
- subtracting the estimate from the near end signal to produce an error signal;
- calculating an echo return loss enhancement using the error signal;
- calculating an attenuation factor using the echo return loss enhancement;
- and
- attenuating a first signal based upon the attenuation factor, wherein the first signal includes a component of the near end signal, wherein:
- the calculating the attenuation factor using the echo return loss enhancement further includes calculating an echo return loss enhancement ceiling value, wherein the echo return loss enhancement ceiling value is calculated from a previous maximum calculated echo return loss enhancement;
- and
- the calculating the attenuation factor using the echo return loss enhancement further includes dividing the echo return loss enhancement by the ceiling value.
A method comprising:
- filtering a far end signal to produce an estimate of an echo in a near end signal;
- subtracting the estimate from the near end signal to produce an error signal;
- calculating an echo return loss enhancement using the error signal;
- calculating an attenuation factor using the echo return loss enhancement;
- and
- attenuating a first signal based upon the attenuation factor, wherein the first signal includes a component of the near end signal, wherein:
- the calculating the attenuation factor using the echo return loss enhancement further includes calculating a noise floor value;
- and
- the calculating the attenuation factor using the echo return loss enhancement further includes multiplying the echo return loss enhancement by the noise floor.
An echo cancellation system comprising:
- an echo canceller, the echo canceller provides an error signal from a near end signal and a far end signal;
- an attenuator, the attenuator attenuates a first signal based upon an attenuation factor, wherein the first signal includes a component of the near end signal;
- and
- an attenuation factor calculator, the attenuation factor calculator calculates an echo return loss enhancement using the error signals, calculates the attenuation factor using the echo return loss enhancement, calculates an echo return loss enhancement ceiling value from a previous maximum calculated echo return loss enhancement, and calculates the attenuation factor by dividing the echo return loss enhancement by the ceiling value.
The echo cancellation system of 18 further comprising:
- a comfort noise generator, the comfort noise generator provides a provides a comfort noise signal;
- a comfort noise attenuator, the comfort noise attenuator attenuates the comfort noise signal based upon the attenuation factor;
- a summer, the summer combines the comfort noise signal attenuated by the comfort noise generator and the first signal attenuated by the attenuator to produce a combined signal.
An echo cancellation system comprising:
- an echo canceller, the echo canceller provides an error signal from a near end signal and a far end signal;
- an attenuator, the attenuator attenuates a first signal based upon an attenuation factor, wherein the first signal includes a component of the near end signal
- means for providing the attenuation factor calculated using an echo return loss enhancement, the echo return loss enhancement is calculated using the error signal and includes calculating a noise floor value and multiplying the echo return loss enhancement by the noise floor value.
Dependencies are inferred from the claim text.