Method and device for determining rhythm units in a musical piece

• US 6,812,394 B2
• Filed: 07/24/2002
• Issued: 11/02/2004
• Est. Priority Date: 05/28/2002
• Status: Active Grant

• Current Assignee: Red Chip Company Limited
• Original Assignee: Red Chip Company Limited
• Inventors: Weissflog, Jörg
• Primary Examiner(s): DONELS, JEFFREY
• Application Number:
  US10/202,328
• Publication Number:
  US 20030221544A1
• Time in Patent Office: 832 Days
• Field of Search: 846/67, 846/03, 846/11, 846/36, 846/52, 846/61, 846/68, 847/14, 846/75--77, 844/84, 84D/IG.11, 84D/IG.12
• US Class Current: 84/667
• CPC Class Codes: G10H 1/40 Rhythm
• CPC Class Codes: G10H 2210/076 for extraction of timing, tempo; Beat detection tempo display G10H2220/081; tempo control G10H2210/375
• CPC Class Codes: G10H 2220/086 Beats per minute [bpm] indicator, i.e. displaying a tempo value, e.g. in words or as numerical value in beats per minute analysis tempo G10H2210/076; tempo or beat alterations G10H2210/375

Abstract

A method for determining rhythm units (beats per minute or BPM) in (digital) audio data forming a musical piece. The audio data is split among a plurality of determination paths wherein it is subdivided into predetermined frequency bands. The data is analyzed for transients in order to determine attack events. In addition, the time intervals between two successive attack events are measured. In this case, the time intervals are averaged and defined as the frequency-band-specific rhythm unit (BPM) of the audio data in the respective determination path. Thus, the rhythm unit which exhibits the highest beat number (BPM number) is selected from the frequency-band-specific rhythm units (BPM) of the determination paths.

Claims

1. A method for determining rhythm units in digital audio data forming a musical piece, wherein the audio data is split among a plurality of determination paths, the method comprising the steps of:

a) subdividing the rhythm units into a plurality of predetermined frequency bands that are extremely narrow and that are at only a very high end or a very low end of an audio frequency spectrum;

b) analyzing the rhythm units for at least one transient to determine a plurality of attack events;

c) measuring a time between two successive attack events; and

d) averaging a plurality of time intervals defined as frequency-band-specific rhythm unit (BPM) of the audio data in respective determination paths wherein a rhythm unit which exhibits a highest beat per minute number (BPM number) is selected from the frequency-band specific rhythm units (BPM) of the determination path.

2. The method as in claim 1, wherein the determined rhythm unit is indicated optically.

3. The method as in claim 1, further comprising the step of determining a maximum average energy of an audio signal in the frequency band of the respective determination path which is determined as a function of time (tw).

4. A device for determining the rhythm units in digital audio data including an input to which audio data is applied, an output, at which a rhythm unit is output and also a plurality of rhythm unit detectors which are connected in parallel between the input and a logic circuit disposed upstream from the output, the detectors comprising the following components:

a) a bandpass filter for separating a frequency range from the audio signal present at the input, said bandpass filters covering at least part of the total bandwidth signal;

b) a transient detector in communication with said bandpass filter said transient detector for determining attack events;

c) a timer for measuring the time intervals between two successive attack events; and

d) a periodicity detector for averaging the time intervals and defining the averaged time interval as a frequency band specific-rhythm unit (BPM) of the audio data in a determination path of said rhythm unit detectors, wherein the logic circuit is designed to select from the frequency band specific rhythm units of the determination paths that rhythm unit (BPM) which has the highest beat number.

5. The device as in claim 4, further comprising a display device coupled downstream from said logic circuit for indicating the determined rhythm unit.

7. The method as in claim 5, wherein said step of determining a maximum average energy of an audio signal includes squaring and averaging an amplitude of an audio signal to determine its energy in the frequency band of the respective determination path.

8. The method as in claim 7, wherein said time window is a rectangular integration window.

9. The method as in claim 7, further comprising the step of delaying said squared amplitude of the audio signal via a delay element, wherein said delay element is subtracted from the input signal of the delay line and summed using a further delay element.

10. The method as in claim 9, further comprising the step of overlapping successive time windows of successive energy determination values by sealing with a constant factor c and then outputting with constant time intervals ts (ts<

tw).

11. The method as in claim 7, further comprising the steps of calculating a local maximum from said determined energy values;

and

applying a linear regression for determining a maximum average of the audio signal.

12. The method as in claim 11, wherein said step of calculating a local maximum includes calculating it as an energy value which is larger than a defined number of subsequent energy values.

13. The method as in claim 12, wherein said step of calculating a local maximum includes determining whether the energy value is larger than a minimum energy level or a separately determined threshold value.

14. The method according to claim 13, further comprising the step of scaling said rhythm unit to ensure that it does not represent a multiple of a basic rhythm unit.

6. A method for determining rhythm units in digital audio data forming a musical piece, wherein the audio data is split among a plurality of determination paths, the method comprising the steps of:

a) subdividing the rhythm units into a plurality of predetermined frequency bands;

b) analyzing the rhythm units for least one transient to determine a plurality of attack events;

c) measuring a time between two successive attack events;

d) averaging a plurality of time intervals defined as frequency-band-specific rhythm unit (BPM) of the audio data in respective determination paths wherein a rhythm units which exhibits a highest beat per minute number (BPM number) is selected from the frequency-band specific rhythm (BPM) of the determination path; and

determining a maximum average energy of an audio signal in the frequency band of the respective determination path which is determined as a function of time (tw).