Control logic for echo canceller with double talk detector

Details Control logic for echo canceller with double talk detector Control logic for echo canceller with double talk detector

1992-06-12

1995-05-23

Dwyer, James L.

Telephonic communications

Echo cancellation or suppression

379410, 379411, H04M 908

Patent

active

054188482

ABSTRACT:
The invention relates to an echo canceller (1, 2, 3, 6) including an adaptive filter (3) which can be inserted between a receive path (r) and a send path (s), and including a non-linear filter (2) which can be inserted in the send path (s). The echo canceller is to have an improved echo cancellation, especially when the state of doubletalk occurs, thus substantially avoiding an erroneous activation of the non-linear filter when the state of doubletalk is detected. For this purpose, it is proposed that the echo canceller (1, 2, 3, 6) comprises an up/down counter (11) provided for counting up with a first value (Z.sub.U) when the state of doubletalk (d) occurs and for counting down with a second value (Z.sub.D) smaller than the first value (Z.sub.U) when the states of non-doubletalk (a, b, c) occur, the non-linear filter (2) being provided to be inserted in the send path (s) only when the state of far-end speech (c) occurs and when the up/down counter (11) reaches a predeterminable small value (Z.sub.N), especially the zero value.

REFERENCES:
patent: 3937907 (1976-02-01), Campanella et al.
patent: 4123626 (1978-10-01), Munter
patent: 4194092 (1980-03-01), Luder
patent: 4360712 (1982-11-01), Horna
patent: 4998241 (1991-03-01), Brox et al.
patent: 5048082 (1991-09-01), Krafft

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