Audio device and playback program for the same
The input signal X of one channel is divided by a multi-stage delay processing device Z −1 and each of the outputs is superimposed by a specified coefficient by a coefficient processing device W 0 , W 1 , . . . , W k . The results are added by an adder, thereby providing a correlation eliminating filter for extracting a signal component from the input signal X of one channel having a high correlation with the input signal Y of the other channel. There is provided a coefficient updating processing device 5 for successively changing the feature of the correlation eliminating filter according to an error signal e obtained from the output signal RES and the input signal Y from the other channel, and the input signal X of one channel. A surround signal is obtained from a difference between the output RES from the correlation eliminating filter and the input signal Y of the other channel. Thus, upon reproduction of a two channels stereo signal, it is possible to generate a surround signal not giving uncomfortable feeling to a listener.
1. An audio device which produces surround signals of a plurality of channels on the basis of audio signals of two channels constituting input signals, characterized in that this audio device is provided with:
a correlation eliminating filter whereby the input signal of a first channel is divided by a multi-stage delay processing device, a specified filter coefficient is superimposed by a coefficient processing device for each of the divided multi-stage outputs so that multi-stage output components are produced, and signal components that have a high correlation with the input signal of a second channel are extracted from the input signal components of the first channel by adding these multi-stage output components; and
an adaptive correlation eliminating device comprising a coefficient updating processing device which constantly varies the characteristics of the correlation eliminating filter on the basis of error signals obtained by means of the output signals and the input signals from the second channel, the input signals from the first channel, and a step size parameter which controls an updating speed of the specified filter coefficient, and
the difference between the output from the correlation eliminating filter and the input signals from the second channel is calculated and output as a surround signal.
2. The audio device according to claim 1 , characterized in that the correlation eliminating filter is constructed from an FIR filter.
3. The audio device according to claim 2 , characterized in that the coefficient updating processing device performs updating of the coefficients on the basis of an LMS algorithm.
4. The audio device according to claim 1 , characterized in that the coefficient updating processing device performs updating of the coefficients on the basis of an NLMS algorithm.
5. The audio device according to claim 1 , characterized in that the correlation eliminating filter is constructed from an IIR filter.
6. The audio device according to claim 1 , characterized in that the coefficient updating processing device performs updating of the coefficients on the basis of an SHARF algorithm.
7. The audio device of claim 1 further comprising
an addition unit adding the input signals from the first channel and the input signals from the second channel and outputting a center signal that is localized in front of or played back in front of a listener.
8. The audio device of claim 7 further comprising
a band limiting filter connected to the addition unit, the band limiting filter receiving the center signal and outputting a bass signal.