Method and system for pitch contour quantization in audio coding

• US 20080275695A1
• Filed: 04/25/2008
• Published: 11/06/2008
• Est. Priority Date: 10/23/2003
• Status: Active Grant

• Current Assignee: RPX Corporation
• Original Assignee: Nokia Corporation
• Inventors: Ramo, Anssi, Heikkinen, Ari, Himanen, Sakari, Nurminen, Jani
• Granted Patent: US 8,380,496 B2
• Time in Patent Office: Days
• US Class Current: 704/207
• CPC Class Codes: G10L 19/032 Quantisation or dequantisation of spectral components
• CPC Class Codes: G10L 19/09 Long term prediction, i.e. removing periodical redundancies, e.g. by using adaptive codebook or pitch predictor

Abstract

A method and device for improving coding efficiency in audio coding. From the pitch values of a pitch contour of an audio signal, a plurality of simplified pitch contour segments are generated to approximate the pitch contour, based on one or more pre-selected criteria. The contour segments can be linear or non-linear with each contour segment represented by a first end point and a second end point. If the contour segments are linear, then only the information regarding the end points, instead of the pitch values, are provided to a decoder for reconstructing the audio signal. The contour segment can have a fixed maximum length or a variable length, but the deviation between a contour segment and the pitch values in that segment is limited by a maximum value.

Claims

1. A method for coding an audio signal for providing parameters indicative of an audio signal, the parameters comprising timewise unaltered pitch contour data containing a plurality of pitch values representative of an audio segment in time, said method comprising:

creating, based on the timewise unaltered pitch contour data, a plurality of simplified pitch contour segment candidates, each candidate corresponding to a sub-segment of the audio signal, wherein each sub-segment has a start-point pitch value and an end-point pitch value and each candidate has a start segment point and an end segment point;

measuring deviation between each of the simplified pitch contour segment candidates and said pitch values in the corresponding sub-segment;

selecting, among said candidates, a plurality of consecutive segment candidates to represent the audio segment based on the measured deviations and one or more pre-selected criteria, wherein the start segment points of at least some selected segment candidates are different from the start-point pitch values of the corresponding sub-segments and the end segment points of at least some selected segment candidates are different from the end-point pitch values of the corresponding sub-segments; and

coding the sub-segment of the audio signal corresponding to the selected segment candidate with characteristics of the selected segment candidate.

2. The method of claim 1, wherein the timewise unaltered pitch contour data in the audio segment in time is approximated by a plurality of selected candidates, corresponding to a plurality of consecutive sub-segments in said audio segment, each of said plurality of selected candidates defined by a first end point and a second end point, and wherein said coding comprises providing information indicative of the end points so as to allow a decoder to reconstruct the audio signal in the audio segment based on the information instead of the input pitch contour data.

3. The method of claim 1, wherein the number of pitch values in some of the consecutive sub-segments is equal to or greater than 3.

4. The method of claim 1, wherein said creating is limited by a pre-selected condition such that the deviation between each of the simplified pitch contour segment candidates and each of said pitch values in the corresponding sub-segment is smaller than or equal to a pre-determined maximum value.

5. The method of claim 4, wherein the created segment candidates have various lengths, and said selecting is based on the lengths of the segment candidates, and the pre-selected criteria include that

the selected candidate has the maximum length among the segment candidates.

6. The method of claim 4, wherein said selecting is based on the lengths of the segment candidates, and the pre-selected criteria include that

the measured deviation is minimum among a group of the candidates having the same length.

7. The method of claim 1, wherein said creating is carried out by adjusting the end segment point of the segment candidates.

8. The method of claim 1, wherein the audio signal comprises a speech signal.

9. The method of claim 2, wherein at least one of the selected candidates is a linear segment.

10. The method of claim 2, wherein at least one of the selected candidates is anon-linear segment.

11. An apparatus comprising:

an input end for receiving timewise unaltered pitch contour data, the timewise unaltered pitch contour data comprising a plurality of pitch values representative of an audio segment of an audio signal in time; and

a data processing module configured to create a plurality of simplified pitch contour segment candidates, responsive to the timewise unaltered pitch contour data, each segment candidate corresponding to a sub-segment of the audio signal, wherein each sub-segment has a start-point pitch value and an end-point pitch value and each candidate has a start segment point and an end segment point, and wherein the processing module is configured to measure deviation between each of the simplified pitch contour segment candidates and said pitch values in the corresponding sub-segment; and

to select, among said candidates, a plurality of consecutive segment candidates to represent the audio segment based on the measured deviations and pre-selected criteria, wherein the start segment points of at least some selected segment candidates are different from the start-point pitch values of the corresponding sub-segments and the end segment points of at least some selected segment candidates are different from the end-point pitch values of the corresponding sub-segments.

12. The apparatus of claim 11, further comprising

a quantization module configured to code the sub-segment of the audio signal corresponding to the selected segment candidate with characteristics of the selected segment candidate.

13. The apparatus of claim 12, wherein the quantization module also configured to provide audio data indicative of the coded pitch contour data in the sub-segment, said coding device further comprising

a storage device, operatively connected to the quantization module to receive the audio data, for storing the audio data in a storage medium.

14. The apparatus of claim 12, further comprising an output end, operatively connected to a storage medium, for providing the coded pitch contour data to the storage medium for storage.

15. The apparatus of claim 12, further comprising an output end for transmitting the coded pitch contour data to the decoder so as to allow the decoder to reconstruct the audio signal also based on the coded pitch contour data.

16. A computer readable medium embodied with a software program for use in conjunction with an audio coding device, the audio coding device providing parameters indicative of the audio signal, the parameters comprising timewise unaltered pitch contour data containing a plurality of pitch values representative of an audio segment in time, said software program comprising:

a code for creating a plurality of simplified pitch contour segment candidates based on the timewise unaltered pitch contour data, each candidate corresponding to a sub-segment of the audio signal, wherein each sub-segment has a start-point pitch value and an end-point pitch value and each candidate has a start segment point and an end segment point;

a code for measuring deviation between each of the simplified pitch contour segment candidates and said pitch values in the corresponding sub-segment; and

a code for selecting, among said candidates, a plurality of consecutive segment candidates to represent the audio segment based on the measured deviations and pre-selected criteria, so as to allow a quantization module to code the sub-segments of the audio signal corresponding to the selected segment candidate with characteristics of the selected segment candidate, wherein the start segment points of at least some selected segment candidates are different from the start-point pitch values of the corresponding sub-segments and the end segment points of at least some selected segment candidates are different from the end-point pitch values of the corresponding sub-segments.

17. An apparatus comprising:

an input for receiving audio data indicative of an audio signal, wherein the audio signal is encoded for providing parameters indicative of the audio signal, the parameters including timewise unaltered pitch contour data containing a plurality of pitch values representative of an audio segment in time, and wherein the timewise unaltered pitch contour data in the audio segment in time is approximated by a plurality of consecutive simplified segments, each simplified segment corresponding to a sub-segment in the audio segment, wherein each of the sub-segments has a start-point pitch value and an end-point pitch value and each of the simplified segments is defined by a first end point and a second end point, and wherein the first end points of at least some simplified segments are different from the start-point pitch values of the corresponding sub-segments and the second end points of at least some simplified segments are different from the end-point pitch values of the corresponding sub-segments, and wherein the received audio data comprises the end points defining the sub-segments; and

a reconstructing module configured to reconstruct the audio segment based on the received audio data.

18. The apparatus of claim 17, wherein the audio data is recorded on an electronic media, and wherein the input of the decoder is operatively connected to electronic media for receiving the audio data.

19. The apparatus of claim 17, wherein the audio data is transmitted through a communication channel, and wherein the input of the decoder is operatively connected to the communication channel for receiving the audio data.

20. An electronic device comprising:

a decoder for reconstructing an audio signal, wherein the audio signal is encoded for providing parameters indicative of the audio signal, the parameters including timewise unaltered pitch contour data containing a plurality of pitch values representative of an audio segment in time, and wherein the timewise unaltered pitch contour data in the audio segment in time is approximated by a plurality of consecutive simplified segments in the audio segment, each simplified segment corresponding to a sub-segment in the audio segment, wherein each of the sub-segments has a start-point pitch value and an end-point pitch value and each of the simplified segments is defined by a first end point and a second end point, and wherein the first end points of at least some simplified segments are different from the start-point pitch values of the corresponding sub-segments and the second end points of at least some simplified segments are different from the end-point pitch values of the corresponding sub-segments, so as to allow the audio segment to be constructed based on the end points defining the sub-segments simplified segments; and

an input configured for receiving audio data indicative of the end points and for providing the audio data to the decoder.

21. The electronic device of claim 20, wherein the audio data is recorded in an electronic medium, and wherein said input is operatively connected to the electronic medium for receiving the audio data.

22. The electronic device of claim 20, wherein the audio data is transmitted through a communication channel, and wherein the input is operatively connected to the communication channel for receiving the audio data.

23. The electronic device of claim 20, comprising a mobile terminal.

24. A communication network, comprising:

a plurality of base stations; and

a plurality of mobile stations communicating with the base stations, wherein at least one of the mobile stations comprises;

a decoder configured for reconstructing an audio signal, wherein the audio signal is encoded for providing parameters indicative of the audio signal, the parameters comprising timewise unaltered pitch contour data containing a plurality of pitch values representative of an audio segment in time, and wherein the timewise unaltered pitch contour data in the audio segment in time is approximated by a plurality of consecutive simplified segments, each simplified segment corresponding to a sub-segment in the audio segment, wherein each of the sub-segments has a start-point pitch value and an end-point pitch value and each of the simplified segments is defined by a first end point and a second end point, and wherein the first end points of at least some simplified segments are different from the start-point pitch values of the corresponding sub-segments and the second end points of at least some simplified segments are different from the end-point pitch values of the corresponding sub-segments; and

an input configured for receiving audio data indicative of the end points from at least one of the base stations for providing the audio data to the decoder.

25. An apparatus comprising:

means for receiving timewise unaltered pitch contour data, the timewise unaltered pitch contour data comprising a plurality of pitch values representative of an audio segment of an audio signal in time; and

means, responsive to the timewise unaltered pitch contour data, for creating a plurality of simplified pitch contour segment candidates, each candidate corresponding to a sub-segment of the audio signal, wherein each sub-segment has a start-point pitch value and an end-point pitch value and each candidate has a start segment point and an end segment point, and

for measuring deviation between each of the simplified pitch contour segment candidates and said pitch values in the corresponding sub-segment, and

for selecting, among said candidates, a plurality of consecutive segment candidates to represent the audio segment based on the measured deviations and pre-selected criteria, wherein the start segment points of at least some selected segment candidates are different from the start-point pitch values of the corresponding sub-segments and the end segment points of at least some selected segment candidates are different from the end-point pitch values of the corresponding sub-segments.

26. The apparatus of claim 25, further comprising

means, responsive to the selected segment candidate, for coding the sub-segment of the audio signal corresponding to the selected segment candidate with characteristics of the selected segment candidate.