Device and method for analyzing an information signal

• US 7,565,213 B2
• Filed: 05/05/2005
• Issued: 07/21/2009
• Est. Priority Date: 05/07/2004
• Status: Expired due to Fees

• Current Assignee: Sony Corporation (Sony Group Corp.)
• Original Assignee: Gracenote, Inc. (RR Donnelley & Sons Company)
• Inventors: Dittmar, Christian, Uhle, Christian, Herre, Jurgen
• Primary Examiner(s): Hudspeth; David R
• Assistant Examiner(s): Kovacek; David
• Application Number:
  US11/123,474
• Publication Number:
  US 20050273319A1
• Time in Patent Office: 1,538 Days
• Field of Search: 704200-2001, 704205-211, 704236-246, 704/270, 704/272, 704E19001-E19002, 704/E19.012, 704E11001-E11007, 381104-107, 700 90- 94
• US Class Current: 700/94
• CPC Class Codes: G10L 25/48 specially adapted for particular use

Abstract

A significant short-time spectrum is extracted from an information signal, the means for extracting being configured to extract such short-time spectra which come closer to a specific characteristic than others. The short-time spectra extracted are then decomposed into component signals using ICA analysis, a component signal spectrum representing a profile spectrum of a tone source which generates a tone corresponding to the characteristic sought. From a sequence of short-time spectra of the information signal and from the profile spectra determined, an amplitude envelope is calculated for each profile spectrum to indicate how a tone source profile spectrum changes over time. The profile spectra and all the amplitude envelopes associated therewith provide a description of the information signal which may be evaluated further, for example for transcription purposes in the case of a music signal.

Claims

1. A device for analyzing an information signal, comprising:

an extractor for extracting significant short-time spectra or significant short-time spectra derived from short-time spectra of the information signal, from the information signal, the extractor being configured to extract such short-time spectra which come closer to a specific characteristic than other short-time spectra of the information signal;

a decomposer for decomposing the extracted short-time spectra into component signal spectra, a component signal spectrum representing a profile spectrum of a tone source which generates a tone corresponding to the characteristic sought for, and another component signal spectrum representing a profile spectrum of another tone source which generates a tone corresponding to the characteristic sought, wherein the decomposer is configured to add the extracted short-time spectra in a weighted manner so as to obtain a reduced number of short-time spectra extracted; and

a calculator for calculating an amplitude envelope for the tone sources, an amplitude envelope for a tone source indicating how a profile spectrum of the tone source changes over time, using the profile spectra and a sequence of short-time spectra representing the information signal.

2. The device as claimed in claim 1, wherein the extractor is configured to pre-process the information signal such that signal portions present in the information signal at higher frequencies are accentuated, in the information signal, compared to signal portions present in the information signal at lower frequencies.

3. The device as claimed in claim 2, wherein the extractor is configured to

subject the information signal to high-pass filtering,

distort the high-pass filtered version of the information signal in a non-linear manner, and

add the non-linearly distorted signal to the original information signal in pre-processing.

4. The device as claimed in claim 3, wherein the extractor is configured to subject the information signal to a time-range/frequency-range conversion to obtain a sequence of short-time spectra, the short-time spectra adjacent in time relating to portions of the information signal which overlap except for a hopping interval defined as a time period between at least some of the short-time spectra adjacent in time.

5. The device as claimed in claim 4, wherein each short-time spectrum comprises a sequence of spectral coefficients, and

wherein the extractor is configured to differentiate the sequence of short-time spectra in terms of time to obtain a sequence of differentiated short-time spectra, a differentiated short-time spectrum providing information about changes in a short-time spectrum compared to a preceding or subsequent short-time spectrum.

6. The device as claimed in claim 5, wherein the extractor is configured to obtain a differentiated short-time spectrum in that for each spectral coefficient, a difference of the spectral coefficient in a current short-time spectrum and a previous or subsequent short-time spectrum is formed.

7. The device as claimed in claim 5, wherein the extractor is configured to rectify the short-time spectra differentiated, so that a differentiated short-time spectrum rectified does not exhibit any negative values.

8. The device as claimed in claim 5, wherein the extractor is configured to determine the significant short-time spectra on the basis of the differentiated short-time spectra.

9. The device as claimed in claim 8, wherein the extractor is configured to sum up, for each differentiated short-time spectrum, spectral coefficients, or values derived from spectral coefficients, so as to obtain a cumulative value for a short-time spectrum, so that a detection function over time results.

10. The device as claimed in claim 9, wherein the extractor is configured to smooth the detection function over time.

11. The device as claimed in claim 9, wherein the extractor is configured to find maxima in the detection function at a point in time, and to use a differentiated short-time spectrum or a short-time spectrum as a significant spectrum having a point in time associated with it at which the detection function exhibits a maximum.

12. The device as claimed in claim 9, wherein the extractor is configured to regard only such maxima of the detection function as significant which are spaced apart in time by more than a predefined time period.

13. The device as claimed in claim 4, wherein the extractor is configured to determine amount spectra as a sequence of short-time spectra, and to use phase information of the short-time spectra when extracting the significant short-time spectra.

14. The device as claimed in claim 1, wherein the decomposer is configured to perform a principal component analysis for dimension reduction so as to obtain processed short-time spectra.

15. The device as claimed in claim 1, wherein the decomposer is configured to perform an independent component analysis to produce a plurality of component signals, a component signal being associated with an information source contributing to the information signal.

16. The device as claimed in claim 1, wherein the calculator for calculating the amplitude envelope is configured to multiply a matrix including the profile spectra, and a matrix including a sequence of short-time spectra of the information signal, so as to obtain the amplitude envelopes for the tone sources.

17. The device as claimed in claim 1, wherein the calculator for calculating the amplitude envelope is configured to further determine a differentiated amplitude envelope using the profile spectra for the tone sources and using the difference spectrogram.

18. The device as claimed in claim 1, further comprising a classifier for classifying the component signals into percussive component signals and non-percussive component signals.

19. The device as claimed in claim 18, wherein the classifier is configured to perform a classification on the basis of the profile spectra and/or the amplitude envelopes.

20. The device as claimed in claim 18, wherein the classifier is configured to extract a feature from the profile spectra or the amplitude envelopes, and to compare it with features of known sources in a database.

21. The device as claimed in claim 1, further comprising an examiner for examining the amplitude envelopes for a tone source so as to accept a maximum in the amplitude envelope as an onset of a signal from the tone source in case the extractor had extracted a significant short-time spectrum at a point in time which was similar within a threshold.

22. The device as claimed in claim 1, wherein the calculator for calculating the amplitude envelope is configured to calculate the amplitude envelope for a tone source in such a manner that the amplitude envelope indicates how an intensity or weighting of a profile spectrum of the tone source changes over time.

23. A method for analyzing an information signal, comprising:

extracting significant short-time spectra or significant short-time spectra derived from short-time spectra of the information signal, from the information signal, the short-time spectra extracted being such short-time spectra which come closer to a specific characteristic than other short-time spectra of the information signal;

decomposing the extracted short-time spectra into component signal spectra, a component signal spectrum representing a profile spectrum of a tone source which generates a tone corresponding to the characteristic sought for, and another component signal spectrum representing a profile spectrum of another tone source which generates a tone corresponding to the characteristic sought, wherein the decomposing includes adding the extracted short-time spectra in a weighted manner so as to obtain a reduced number of short-time spectra extracted; and

calculating an amplitude envelope for the tone sources, an amplitude envelope for a tone source indicating how a profile spectrum of the tone source changes over time, using the profile spectra and a sequence of short-time spectra representing the information signal.

24. A tangible computer storage medium having stored thereon a computer program having a program code for performing a method for analyzing an information signal, which when executed by a computer, results in the computer performing the method comprising:

extracting significant short-time spectra or significant short-time spectra derived from short-time spectra of the information signal, from the information signal, the short-time spectra extracted being such short-time spectra which come closer to a specific characteristic than other short-time spectra of the information signal;

decomposing the extracted short-time spectra into component signal spectra, a component signal spectrum representing a profile spectrum of a tone source which generates a tone corresponding to the characteristic sought for, and another component signal spectrum representing a profile spectrum of another tone source which generates a tone corresponding to the characteristic sought, wherein the decomposing includes adding the extracted short-time spectra in a weighted manner so as to obtain a reduced number of short-time spectra extracted; and

calculating an amplitude envelope for the tone sources, an amplitude envelope for a tone source indicating how a profile spectrum of the tone source changes over time, using the profile spectra and a sequence of short-time spectra representing the information signal,

when the computer program runs on a computer.