Patent ID: 6856653

Claim:
An echo canceller apparatus comprising: loudspeaker means for audibly reproducing a first input digital audio signal which is transmitted from a remote location; microphone means for generating a second input digital audio signal in response to incident sound waves; first sub-band separating means for converting said first input digital audio signal to a first plurality of sub-band signals; second sub-band separating means for converting said second input digital audio signal to a second plurality of sub-band signals; a plurality of adaptive filters for controllably filtering said first plurality of sub-band signals to obtain corresponding modified sub-band signals; means for deriving respective differences between said modified sub-band signals and corresponding ones of said second sub-band signals, as respective error signals; filter coefficient updating means for utilizing values of said error signals to modify filter coefficients of respective ones of said adaptive filters; and sub-band combining means for combining said error signals into a single digital audio signal, to be transmitted to said remote location, wherein; each of said first and second sub-band separating means comprises a digital signal sub-band separating apparatus including: a plurality of filters corresponding to respective frequency bands, for separating said input digital audio signal into said plurality of sub-band signals; and decimation means for applying digital signal sample decimation to each of said sub-band signals, wherein; said digital signal sub-band separating apparatus comprises, as a prototype filter of said plurality of filters, a FIR (finite impulse response) low-pass filter which is configured to have an asymmetric impulse response.