Method and apparatus for removing or isolating voice or instruments on stereo recordings

1. A method for separation of at least two sources in an audio signal, comprising the steps of:

inputting a two-channel audio signal mixture;

performing an STFT decomposition of each of said channels, comprising an FFT for each overlapping time frame, to form left and right complex-valued spectrograms X 1 (ω, t) and X 2 (ω, t);

estimating a panning parameter at each spectrogram point and a phase offset between channels, where the phase offset may be converted to a delay estimate;

estimating mixing parameters for all sources based upon said estimated panning parameters and said phase offset;

given mixing parameters for each source and frequency band activity for each source, demixing said sources by creating masks from spatial window functions in a parameter space including detected panning and detected phase offset;

based on a detected panning and phase for each spectrogram point and said mixing parameters, assigning some fraction of the energy in said spectrogram point to each source;

for each spectrogram, employing a phase function using either an original input phase, or a phase that results when normalized weighted and delayed subtraction is performed, to eliminate any source existing in said audio signal;

producing two output spectrograms for each source, wherein 2N spectrograms result; and

inverting said output spectrograms and providing a final output of N time domain stereo source signal estimates.

2. The method of claim 1 , further comprising the step of:

obtaining said fraction by performing normalized weighted and delayed subtraction of one channel from another.

3. The method of claim 1 , further comprising the step of:

raising said fraction to an arbitrary power to create more attenuation.

4. The method of claim 1 , further comprising the step of:

using a minimum of several fractions as a final fraction.

5. The method of claim 4 , wherein said several fractions correspond to fractions used to eliminate each of one or more other sources in said input.

6. The method of claim 4 , wherein said several fractions correspond to sources with arbitrary mixing parameters, so long as said parameters are in a closed shape around a target source's mixing parameters.

7. The method of claim 6 , wherein said closed shape is an ellipse in a panning and phase (or delay) parameter space.

8. The method of claim 1 , further comprising the step of:

performing a linear interpolation between said two phase functions.

9. The method of claim 1 , further comprising the step of:

re-panning said sources using their original panning data.

10. The method of claim 1 , further comprising the step of: making both said X 1 (ω, t) and X 2 (ω, t) spectrogram magnitudes the same by multiplying a combined magnitude said input audio signal by a final fraction.

11. The method of claim 1 , wherein said input is any of music and speech.

12. A method for separation of at least two audio sources, comprising the steps of:

inputting a two-channel audio signal mixture;

performing an STFT decomposition of each of said channels, comprising an FFT for each overlapping time frame, to form left and right spectrograms X 1 (ω, t) and X 2 (ω, t);

estimating panning, phase offset, and loudness parameters for each spectrogram point;

given the estimated parameters and frequency band of each input point, finding a corresponding bin in a histogram of most likely and expected median source values;

assigning spectrogram energy to said sources by multiplying a fraction of input corresponding to a most likely or median source value from a corresponding histogram bin;

using original phase data or that from a special phase function created when subtracting a weighted version of said left spectrogram X 1 (ω, t) from a weighted version of said right spectrogram X 2 (ω, t), or an interpolation between these two values; and

inverting each source estimate spectrogram to obtain time domain source signal estimates.

13. The method of claim 12 , further comprising the step of:

re-panning the said source estimates using the original input spectrogram panning data.

14. The method of claim 12 , further comprising the step of:

making both spectrogram magnitudes the same.

15. The method of claim 12 , wherein said input comprises any of music and speech.