Fraunhofer-gesellschaft Zur Foerderung Der Angewandten Forschung E.v.

M2any Gmbh

Markus Cremer

Christian Uhle

Michael Saupe

Jan Rohden

Markus Van Pinxteren

Oliver Hellmuth

Jürgen Herre

Thorsten Kastner

Eric Allamanche

Matthias Gruhne

Juergen Herre

Claas Derboven

Frank Streitenberger

Martin Weis

An apparatus for producing a fingerprint signal from an audio signal includes a means for calculating energy values for frequency bands of segments of the audio signal which are successive in time, so as to obtain, from the audio signal, a sequence of vectors of energy values, a means for scaling the energy values to obtain a sequence of scaled vectors, and a means for temporal filtering of the sequence of scaled vectors to obtain a filtered sequence which represents the fingerprint, or from which the fingerprint may be derived. Thus, a fingerprint is produced which is robust against disturbances due to problems associated with coding or with transmission channels, and which is especially suited for mobile radio applications.

Apparatus and method for robust classification of audio signals, and method for establishing and operating an audio-signal database, as well as computer program

For producing a fingerprint of an audio signal, use is made of information defining a plurality of predetermined fingerprint modi, all of the fingerprint modi relating to the same type of fingerprint, the fingerprint modi, however, providing different fingerprints differing from each other with regard to their data volume, on the one hand, and to their characterizing strength for characterizing the audio signal, on the other hand, the fingerprint modi being pre-determined such that a fingerprint in accordance with a fingerprint modus having a first characterizing strength is convertible to a fingerprint in accordance with a fingerprint modus having a second characterizing strength, without using the audio signal. A predetermined fingerprint modus of the plurality of predetermined fingerprint modi is set and subsequently used for computing a fingerprint using the audio signal. The convertibility feature of the fingerprints having been produced by the different fingerprint modi enables setting a flexible compromise between the data volume and the characterizing strength for certain applications without having to re-generate a fingerprint database with each change of the fingerprint modus. Fingerprint representations scaled with regard to time or frequency may readily be converted to a different fingerprint modus.

Method and apparatus for producing a fingerprint, and method and apparatus for identifying an audio signal

For grouping temporal segments of an audio piece, which is structured into main parts repeatedly occurring in the audio piece, into various segment classes, at first a similarity representation for the segments is provided, wherein the similarity representation for each segment comprises an associated plurality of similarity values, wherein the similarity values indicate how similar the segment is to every other segment of the audio piece. Hereupon, using the similarity values associated with the segment, a similarity threshold value for a segment is calculated in order to then associate a segment with a segment class when the similarity value of the segment meets a predetermined relation with reference to the similarity threshold value. With this, clustering is achieved, which also works efficiently and correctly where there are segments with strongly different or almost equal combined similarity values.

Apparatus and method for grouping temporal segments of a piece of music

An encoded rhythmic pattern has several groups of velocity values, wherein the velocity values are sorted, such that the groups are included in sequence in an encoded rhythmic pattern. Now, the velocity values concentrated at the beginning of the encoded rhythmic pattern have a higher importance for characterizing the rhythmic gist of a piece of music than velocity values included in additional groups of velocity values. By using such an encoded rhythmic pattern, an efficient database access can be performed.

Apparatus and method for generating an encoded rhythmic pattern

For the segment class designation the temporal position of segments in two candidate segment classes is used for the stanza/refrain selection by means of a segment class designation means, wherein the highest-order segment class is designated as refrain segment class only when it has a segment following temporally later in the audio piece than the latest segment of the other candidate segment class. With this, segment class labeling with a low error rate is achieved, which can at the same time be implemented with easy effort and is further predestined for automated flow.

Apparatus and method for designating various segment classes

For changing a segmentation of an audio piece after a segment class assignment, at first a short segment is selected, which has a length shorter than a predetermined minimum length. This short segment is preferably merged with the corresponding successor segment or predecessor segment using information on a segment class membership of the short segment itself, but also the successor segment or the predecessor segment, in order to obtain a changed segmentation of the audio signal. With this, a not over-segmented segment representation of the audio signal is obtained, which further includes all audio information, i.e. is not a representation of the audio piece with holes.

Apparatus and method for changing a segmentation of an audio piece

An apparatus for analyzing an audio signal with regard to rhythm information of the audio signal by using an autocorrelation function comprises a filter bank for separating the audio signal into at least two sub-band signals. The sub-band signals are examined with regard to periodicities by an autocorrelation function, to obtain rhythm raw-information for the at least two sub-band signals. To reduce or eliminate the ambiguities of the autocorrelation function for periodical signals, the rhythm raw-information is postprocessed to obtain post-processed rhythm raw-information for the sub-band signal. The rhythm information of the audio signal is established based on the postprocessed rhythm raw-information. By the sub-band-wise ACF postprocessing, ACF ambiguities are already eliminated where they originate, and rhythm portions are added at double tempi, which an autocorrelation function processing does normally not provide, so that, as a result, a more robust determination of the rhythm information of the audio signal arises.

Apparatus for analyzing an audio signal with regard to rhythm information of the audio signal by using an autocorrelation function

A tone smoothing is performed such that to each time section of a melody line segment a number is associated such that for all groups of directly neighboring time sections, to which the same spectral component is associated by the melody line segment, the numbers associated with the directly neighboring time sections are different numbers from one to the number of the directly neighboring time sections, for each spectral component that is associated with one of the time sections of the melody line segment, the numbers of those groups are added up to which time sections of the same the respective spectral component is associated by the melody line segment, a smoothing spectral component is determined as the spectral component for which the greatest summing-up results, and the melody line segment is changed, by associating the determined smoothing spectral component to each time section of the melody line segment. By this, in particular the inadequacy of monophonic audio signals is considered, usually comprising a transient process at beginnings of notes, so that only to the end of the notes the desired note pitch is achieved.

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Ilmenau, Germany

Markus Cremer