Removal of Long Pulses from Audio Signals Using Two-pass Split-window Filtering

Paulo A. A. Esquef, Luiz W. P. Biscainho, Vesa Välimäki, and Matti Karjalainen

This is a companion webpage with sound examples to the homonym paper presented at the 112th AES Convention, Munich, Germany, May 2002, Preprint 5535

1. Abstract

This paper addresses the restoration of audio signals proceeding from old recordings, and focuses on long-pulse removal. We propose a new two-stage method to estimate the waveform of each long pulse from the observed noisy signal. First, an initial estimate for the pulse shape is obtained via a non-linear filtering scheme called two-pass split-window (TPSW) filtering. Then, this estimate is further smoothed through a piecewise polynomial fitting. The degree of smoothness of the estimate can be controlled by adjusting either the TPSW parameters or the length of the segments to be fitted. The proposed method has low computational complexity, it is not constrained by the assumption of shape similarity among pulse waveforms, and can be successfully applied for removing overlapping pulses.

2. Animated illustration of the variable-length TPSW filtering (section1.3).

Movie description: the beginning of a segment corrupted with a pulse is the blue curve seen in the first plot. The sliding split-window is seen as red boxes while the output of the first pass is plotted also in red in the curve displayed below. The substituted sequence, which is superposed to the output of the first passs, is plotted in black. Again, on the second pass, the split-window is seen as the sliding red boxes while the corresponding output is drawn in red in the plot below. Finally, the corrupted segment appears in blue for comparison purposes. Place the mouse pointer on the image below to run the movie! Or click HERE to download the .avi file (about 5 Mb).


3. Tests with artificially corrupted signals

3.1 Description of the test signals

a) pop: a 14-second long exerpt of Finnish pop music with male and female singing;

b) classic: a 13-second long excerpt of orchestral music with a continuously sustained bass chord, slowly varying string passage and percussion;

c) ethnic: an 11-second long excerpt of Brazilian music featuring male singing, folk fiddle, and prominent percussion beating;

3.2 Restoration Results

3.2.1 pop

3.2.2 classic

3.2.3 ethnic

4. Originally Corrupted Signal (taken from S. Godsill's webpage, track 6 (source))

4.1. track 6 (source)

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Last modified: 16.09.2002
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