Device for processing echo, particularly acoustic echo in a telephone line
First Claim
1. A device for processing a real echo between first and second transmission channels, said device comprisingecho cancellation means coupled to said first channel to be responsive to a first signal in said first channel and coupled to said second channel to be responsive to a second signal and said real echo in said second channel for producing a third signal containing components representing said second signal and a difference between said real echo and an estimated echo, said estimated echo resulting from a real echo identified by adaptive filtration in said echo cancellation means from said first and third signals,means for detecting in said third signal said components representing the difference between the real echo and estimated echo and said second signal only in response to the level of said third signal being greater than a first threshold, said components representing the difference between the real echo and estimated echo and said second signal being detected by correlation of said first and third signals andadaptation gain controlling means for gain-controlling the adaptation in the filtration of said echo cancelling means for modifying the adaptation gain while the second signal is detected as not being present in the second channel and for inhibiting filtration modification while said second signal is detected as being present in the second channel.
1 Assignment
0 Petitions
Accused Products
Abstract
The device comprises an echo cancelling circuit receiving a first signal and a second signal and a real echo between channels for producing a third signal containing the second signal and a difference between the real echo and the estimated echo. Detectors detect the echo difference and the second signal in the third signal when the level of the third signal exceeds a predetermined threshold. Circuits gain-control the adaptation in the adaptive filtration of the echo cancelling circuit in such a way as to modify the adaptation gain when the second signal is not detected and to prohibit all filtration modifications as long as the second signal is detected. For instance, for an acoustic echo in a telephone set, the echo is not processed when the third signal contains a local speech signal as second signal.
69 Citations
20 Claims
-
1. A device for processing a real echo between first and second transmission channels, said device comprising
echo cancellation means coupled to said first channel to be responsive to a first signal in said first channel and coupled to said second channel to be responsive to a second signal and said real echo in said second channel for producing a third signal containing components representing said second signal and a difference between said real echo and an estimated echo, said estimated echo resulting from a real echo identified by adaptive filtration in said echo cancellation means from said first and third signals, means for detecting in said third signal said components representing the difference between the real echo and estimated echo and said second signal only in response to the level of said third signal being greater than a first threshold, said components representing the difference between the real echo and estimated echo and said second signal being detected by correlation of said first and third signals and adaptation gain controlling means for gain-controlling the adaptation in the filtration of said echo cancelling means for modifying the adaptation gain while the second signal is detected as not being present in the second channel and for inhibiting filtration modification while said second signal is detected as being present in the second channel.
-
13. A telephony device comprising:
-
a first channel in which is developed a first voice representing signal; a second channel coupled with the first channel and in which is developed a second signal including a first component that is a replica of the first voice signal and a second component representing an actual echo in the second signal; means responsive to the first voice representing signal for deriving an echo estimate component; means responsive to the echo estimate component, the first component and the second component for deriving a third signal having a magnitude representing the first component and the deviation between the actual echo and the echo estimate component, the magnitude representing the first component and the deviation between the actual echo and the echo estimate component being derived by correlation of said first and third signals, the third signal being coupled to the means for deriving the echo estimate component for controlling the echo estimate component; means responsive to the third signal for detecting the presence and absence of a voice signal in the second channel and for controlling the gain of the echo estimate component deriving means so that the echo estimate component is varied in amplitude as a function of the amplitude of at least one of the voice representing signals in response to the second signal being detected as being absent from the second channel and for not varying the echo estimate component in response to the second signal being detected as being present in the second channel. - View Dependent Claims (16, 19)
-
-
14. A telephony device for processing a real echo between a first channel in which is developed a first voice representing signal and a second channel coupled with the first channel and in which is developed a second signal including a first component that is a replica of the first voice signal and a second component representing an actual echo in the second signal;
-
the processing device comprising; means responsive to the first voice representing signal for deriving an echo estimate component; means responsive to the echo estimate component, the first component and the second component for deriving a third signal having a magnitude representing the first component and the deviation between the actual echo and the echo estimate component, the third signal being coupled to the means for deriving the echo estimate component for controlling the echo estimate component, the magnitude representing the first component and the deviation between the actual echo and the echo estimate component being derived by correlation of said first and third signals; means responsive to the third signal for detecting the presence and absence of a voice signal in the second channel and for controlling the gain of the echo estimate component deriving means so that the echo estimate component is varied in amplitude as a function of the amplitude of at least one of the voice representing signals in response to the second signal being detected as being absent from the second channel and for not varying the echo estimate component in response to the second signal being detected as being present in the second channel. - View Dependent Claims (17, 20)
-
Specification