Temporal interpolation of adjacent spectra

摘要

Embodiments of the present invention exploit redundancy of succeeding FFT spectra and use this redundancy for computing interpolated temporal supporting points. An analysis filter bank converts overlapped sequences of an audio (ex. loudspeaker) signal from a time domain to a frequency domain to obtain a time series of short-time loudspeaker spectra. An interpolator temporally interpolates this time series. The interpolation is fed to an echo canceller, which computes an estimated echo spectrum. A microphone analysis filter bank converts overlapped sequences of an audio microphone signal from the time domain to the frequency domain to obtain a time series of short-time microphone spectra. The estimated echo spectrum is subtracted from the microphone spectrum. Further signal enhancement (filtration) may be applied. A synthesis filter bank converts the filtered microphone spectra to the time domain to generate an echo compensated audio microphone signal. Computational complexity of signal processing systems can, therefore, be reduced.

主权项

1. A method for echo compensation of at least one audio microphone signal that includes an echo signal contribution due to an audio loudspeaker signal in a loudspeaker-microphone system, the method comprising:
converting overlapped sequences of the audio loudspeaker signal from a time domain to a frequency domain and obtaining a time series of short-time loudspeaker spectra with a predetermined number of sub-bands, wherein the sequences have a predetermined sequence length and an amount of overlapping of the overlapped sequences predetermined by a loudspeaker sub-sampling rate; temporally interpolating the time series of short-time loudspeaker spectra, including, for each pair of temporally adjacent short-time loudspeaker spectra, calculating an interpolated short-time loudspeaker spectrum by weighted addition of the temporally adjacent short-time loudspeaker spectra; computing an estimated echo spectrum with its sub-band components for at least one current loudspeaker spectrum by weighted adding of a current short-time loudspeaker spectrum and previous short-time loudspeaker spectra, up to a predetermined maximum time delay, wherein: first filter coefficients are used for weighting the current loudspeaker spectrum and the corresponding previous short-time loudspeaker spectra with increasing time delay; second filter coefficients are used for weighting the interpolated short-time loudspeaker spectra temporally adjacent to the current loudspeaker spectrum and the corresponding previous short-time loudspeaker spectra; and the first and second filter coefficients are estimated by an adaptive algorithm; converting overlapped sequences of the audio microphone signal from the time domain to the frequency domain and obtaining a time series of short-time microphone spectra with a predetermined number of sub-bands, wherein the sequences have a predetermined sequence length and an amount of overlapping of the overlapped sequences predetermined by a microphone sub-sampling rate; adaptively filtering the time series of short-time microphone spectra of the microphone signal by at least subtracting a corresponding estimated echo spectrum from a corresponding microphone spectrum, where the first and second filter coefficients are applied and sub-band components of the spectra are used for the subtraction; converting the filtered time series of short-time spectra of the microphone signal to overlapped sequences of a filtered audio microphone signal; and overlapping the sequences of the filtered audio microphone signal to generate an echo compensated audio microphone signal.