System and method for compressed domain beat detection in audio bitstreams

• US 20020178012A1
• Filed: 09/28/2001
• Published: 11/28/2002
• Est. Priority Date: 01/24/2001
• Status: Active Grant

• Current Assignee: Nokia Corporation
• Original Assignee: Nokia Corporation
• Inventors: Wang, Ye, Vilermo, Miikka
• Granted Patent: US 7,050,980 B2
• Time in Patent Office: Days
• US Class Current: 704/503
• CPC Class Codes: G10H 1/0058 Transmission between separate instruments or between individual components of a musical system G10H1/0083 takes precedence
• CPC Class Codes: G10H 2240/061 MP3, i.e. MPEG-1 or MPEG-2 Audio Layer III, lossy audio compression
• CPC Class Codes: G10H 2240/185 Error prevention, detection or correction in files or streams for electrophonic musical instruments
• CPC Class Codes: G10H 2240/245 ISDN [Integrated Services Digital Network]
• CPC Class Codes: G10H 2240/251 Mobile telephone transmission, i.e. transmitting, accessing or controlling music data wirelessly via a wireless or mobile telephone receiver, analog or digital, e.g. DECT GSM, UMTS smartphone, PDA or palmtop used for musical purposes G10H2230/015; mobile ringtone G10H2230/021
• CPC Class Codes: G10H 2240/295 Packet switched network, e.g. token ring circuit-switched networks, e.g. traditional analog telephone transmission G10H2240/241
• CPC Class Codes: G10H 2240/305 Internet or TCP/IP protocol use for any electrophonic musical instrument data or musical parameter transmission purposes
• CPC Class Codes: G10L 19/005 Correction of errors induced by the transmission channel, if related to the coding algorithm
• CPC Class Codes: G10L 19/0212 using orthogonal transformation

Abstract

A system and method for detecting beats in a compressed audio domain is disclosed where a beat detector functions as part of an error concealment system in an audio decoding section used in audio information transfer and audio download-streaming system terminal devices such as mobile phones. The beat detector includes a MDCT coefficient extractor, a band feature value analyzer, a confidence score calculator; and a converging and storage unit. The method provides beat detection by means of beat information obtained using both MDCT coefficients as well as window-switching information. A baseline beat position is determined using MDCT coefficients obtained from the audio bitstream which also provides a window-switching pattern. A window-switching beat position is compared with the baseline beat position and, if a predetermined condition is satisfied, the window-switching beat position is validated as a detected beat.

Claims

1. A method for detecting beats in a compression encoded audio bitstream, said method comprising the steps of:

determining a baseline beat position using modified discrete cosine transform coefficients obtained from the audio bitstream;

deriving a search window-switching pattern from the audio bitstream;

determining a window-switching beat position using said search window-switching pattern;

comparing said baseline beat position with said window-switching beat position; and

validating said window-switching beat position as a detected beat if a predetermined condition is satisfied.

2. A method as in claim 1 further comprising the step of determining an inter-beat interval related to said baseline beat position.

3. A method as in claim 2 further comprising the step of storing said window-switching beat position and said inter-beat interval for subsequent retrieval.

4. A method as in claim 1 wherein said step of determining a baseline beat position comprises the step of determining at least one beat candidate and an inter-onset interval.

5. A method as in claim 4 wherein said step of determining a baseline beat position further comprises the step of checking said at least one beat candidate for reliability using a predetermined confidence threshold value.

6. A method as in claim 4 further comprising the step of converging two or more said beat candidates to a single beat candidate.

7. A method as in claim 1 wherein said step of deriving baseline beat information from the audio bitstream comprises the step of deriving an energy value for at least one subband from the compression encoded audio bitstream.

8. A method as in claim 7 wherein said subband comprises a member of the group consisting of a frequency interval from 0 to 459 Hz, a frequency interval from 460 to 918 Hz, a frequency interval from 919 to 1337 Hz, a frequency interval from 1.338 to 3.404 kHz, a frequency interval from 3.405 to 7.462 kHz, and a frequency interval from 7.463 to 22.05 kHz.

9. A method as in claim 7 wherein said step of deriving a beat position comprises the step of identifying a maximum energy value within a search window.

10. A method as in claim 7 wherein said step of deriving an energy value for at least one subband comprises the step of deriving an absolute energy value.

11. A method as in claim 7 wherein said step of deriving an energy value for at least one subband comprises the step of deriving an element-to-mean energy value.

12. A method as in claim 7 wherein said step of deriving an energy value for at least one subband comprises the step of deriving a differential energy value.

14. The beat detector as in claim 13 wherein said feature value comprises a member of the group consisting of an absolute energy value, an element-to-mean energy value, and a differential energy value.

15. The beat detector as in claim 14 further comprising an element-to-mean ratio threshold comparator.

13. A beat detector suitable for placement into an audio device conforming to a compression-encoded audio transmission protocol, said beat detector comprising:

a modified discrete cosine transform coefficient extractor, for obtaining transform coefficients;

at least one band feature value analyzer for analyzing a feature value for a related band;

a confidence score calculator; and

a converging and storage unit for combining two or more said analyzed band feature values.

16. An audio encoder suitable for use with a compression-encoded audio transmission protocol, said audio encoder comprising:

a beat detector including

a modified discrete cosine transform coefficient extractor, for obtaining transform coefficients;

at least one band feature value analyzer for analyzing a feature value for a related band;

a confidence score calculator; and

means for including beat detection information as side information in audio transmission.

17. An audio decoder suitable for use with a compression-encoded audio transmission protocol, said audio decoder comprising:

a beat detector for providing beat position information, said beat detector including

a modified discrete cosine transform coefficient extractor, for obtaining transform coefficients;

at least one band feature value analyzer for analyzing a feature value for a related band;

a confidence score calculator; and

error concealment means for concealing packet loss in audio transmission by utilizing said beat position to identify audio data for replacement of packet loss.