Speech coding method, device, coding module, system and software program product for pre-processing the phase structure of a to be encoded speech signal to match the phase structure of the decoded signal

• US 7,523,032 B2
• Filed: 12/19/2003
• Issued: 04/21/2009
• Est. Priority Date: 12/19/2003
• Status: Expired due to Fees

• Current Assignee: Nokia Corporation
• Original Assignee: Nokia Corporation
• Inventors: Heikkinen, Ari, Ramo, Anssi, Himanen, Sakari
• Primary Examiner(s): Smits; Talivaldis Ivars
• Application Number:
  US10/742,645
• Publication Number:
  US 20050137858A1
• Time in Patent Office: 1,950 Days
• Field of Search: 704/207, 704/219, 704/220
• US Class Current: 704/207
• CPC Class Codes: G10L 19/08 Determination or coding of the excitation function; Determination or coding of the long-term prediction parameters
• CPC Class Codes: G10L 19/16 Vocoder architecture
• CPC Class Codes: G10L 19/265 Pre-filtering, e.g. high frequency emphasis prior to encoding

Abstract

The invention relates to a method for use in parametric speech coding. In order to enable an improved parametric coding of speech signals, the method comprises a first step of pre-processing a to be encoded speech based signal such that a phase structure of the to be encoded speech based signal is approached to a phase structure which is obtained when the to be encoded speech based signal is parametrically encoded and decoded again. Only in a second step, a parametric encoding is applied to this pre-processed to be encoded speech based signal. The invention relates equally to a corresponding device, to a corresponding coding module, to a corresponding system and to a corresponding software program product.

Claims

1. A method for use in speech coding, said method comprising:

pre-processing a to be encoded speech based signal on a frame-by-frame basis such that a phase structure of said to be encoded speech based signal is approached to a phase structure which would be obtained if said to be encoded speech based signal was encoded and decoded; and

applying an encoding to said pre-processed to be encoded speech based signal;

wherein pre-processing said to be encoded speech based signal comprises for a respective frame of said to be encoded speech signal;

estimating a pitch for said frame;

determining a synthetic phase contour over said frame based on said pitch estimate and a pitch estimate for a preceding frame;

locating at least one pitch pulse position in said determined synthetic phase contour;

locating at least one pitch pulse position in said frame of said to be encoded speech based signal; and

modifying said to be encoded speech based signal in said frame such that the at least one pitch pulse position is shifted to the at least one pitch pulse position of said synthetic phase contour.

2. The method according to claim 1, wherein said speech coding is a parametric speech coding employing at least one parameter indicative of the phase of said to be encoded speech based signal.

3. The method according to claim 1, wherein said pre-processing comprises modifying a respective frame of said to be encoded speech based signal such that a phase contour of said pre-processed to be encoded speech based signal over said frame corresponds basically to a synthetic phase contour determined from pitch estimates for said to be encoded speech based signal.

4. The method according to claim 1, wherein said at least one pitch pulse in said to be encoded signal is located by means of a signal energy contour.

5. The method according to claim 1, wherein said to be encoded speech signal is modified by means of time warping.

6. The method according to claim 1, wherein for those frames of said to be encoded speech signal in which no reliable pitch pulse position is found, a coding without pre-processing of said to be encoded signal is employed.

7. The method according to claim 1, wherein said to be encoded speech based signal is one of an original speech signal and a linear prediction residual of an original speech signal.

8. The method according to claim 1, wherein said pre-processed to be encoded speech based signal is encoded by one of an open-loop parametric coding and a closed-loop parametric coding.

9. A device for performing a speech coding, said device comprising:

a pre-processing portion adapted to pre-process a to be encoded speech based signal on a frame-by-frame basis such that a phase structure of said to be encoded speech based signal is approached to a phase structure which would be obtained if said to be encoded speech based signal was encoded and decoded; and

a coding portion which is adapted to apply an encoding to a to be encoded speech based signal;

wherein said pre-processing by said pre-processing portion comprises for a respective frame of a to be encoded speech signal;

estimating a pitch for said frame;

determining a synthetic phase contour over said frame based on said pitch estimate and a pitch estimate for a preceding frame;

locating at least one pitch pulse position in said determined synthetic phase contour;

locating at least one pitch pulse position in said frame of said to be encoded speech based signal; and

modifying said to be encoded speech based signal in said frame such that the at least one pitch pulse position is shifted to the at least one pitch pulse position of said synthetic phase contour.

10. The device according to claim 9, wherein said coding portion applies a parametric speech coding to a to be encoded speech based signal employing at least one parameter indicative of the phase of said to be encoded speech based signal.

11. The device according to claim 9, wherein said pre-processing by said pre-processing portion comprises modifying a respective frame of a to be encoded speech based signal such that a phase contour of said pre-processed to be encoded speech based signal over said frame corresponds basically to a synthetic phase contour determined from pitch estimates for said to be encoded speech based signal.

12. The device according to claim 9, wherein said device is one of a mobile terminal and a network element.

13. A coding module for performing a speech coding, said coding module comprising:

a pre-processing portion adapted to pre-process a to be encoded speech based signal on a frame-by-frame basis such that a phase structure of said to be encoded speech based signal is approached to a phase structure which would be obtained if said to be encoded speech based signal was encoded and decoded; and

a coding portion which is adapted to apply an encoding to a to be encoded speech based signal;

wherein said pre-processing by said pre-processing portion comprises for a respective frame of a to be encoded speech signal;

estimating a pitch for said frame;

determining a synthetic phase contour over said frame based on said pitch estimate and a pitch estimate for a preceding frame;

locating at least one pitch pulse position in said determined synthetic phase contour;

locating at least one pitch pulse position in said frame of said to be encoded speech based signal; and

modifying said to be encoded speech based signal in said frame such that the at least one pitch pulse position is shifted to the at least one pitch pulse position of said synthetic phase contour.

14. The coding module according to claim 13, wherein said coding portion applies a parametric speech coding to a to be encoded speech based signal employing at least one parameter indicative of the phase of said to be encoded speech based signal.

15. The coding module according to claim 13, wherein said pre-processing by said pre-processing portion comprises modifying a respective frame of a to be encoded speech based signal such that a phase contour of said pre-processed to be encoded speech based signal over said frame corresponds basically to a synthetic phase contour determined from pitch estimates for said to be encoded speech based signal.

16. A system comprising at least one device for performing a speech coding, said at least one device comprising:

a pre-processing portion adapted to pre-process a to be encoded speech based signal on a frame-by-frame basis such that a phase structure of said to be encoded speech based signal is approached to a phase structure which would be obtained if said to be encoded speech based signal was encoded and decoded; and

a coding portion which is adapted to apply an encoding to a to be encoded speech based signal;

wherein said pre-processing by said pre-processing portion of said at least one device comprises for a respective frame of a to be encoded speech signal;

estimating a pitch for said frame;

determining a synthetic phase contour over said frame based on said pitch estimate and a pitch estimate for a preceding frame;

locating at least one pitch pulse position in said determined synthetic phase contour;

locating at least one pitch pulse position in said frame of said to be encoded speech based signal; and

modifying said to be encoded speech based signal in said frame such that the at least one pitch pulse position is shifted to the at least one pitch pulse position of said synthetic phase contour.

17. The system according to claim 16, wherein said coding portion of said at least one device applies a parametric speech coding to a to be encoded speech based signal employing at least one parameter indicative of the phase of said to be encoded speech based signal.

18. The system according to claim 16, wherein said pre-processing by said pre-processing portion of said at least one device comprises modifying a respective frame of a to be encoded speech based signal such that a phase contour of said pre-processed to be encoded speech based signal over said frame corresponds basically to a synthetic phase contour determined from pitch estimates for said to be encoded speech based signal.

19. The system according to claim 16, wherein said at least one device is at least one of a mobile terminal and a network element.

20. A coding module in which a software code for use in speech coding is stored, said software code realizing the following steps when running in a processing unit:

pre-processing a to be encoded speech based signal on a frame-by-frame basis such that a phase structure of said to be encoded speech based signal is approached to a phase structure which would be obtained if said to be encoded speech based signal was encoded and decoded; and

applying an encoding to said pre-processed to be encoded speech based signal;

wherein pre-processing said to be encoded speech based signal comprises for a respective frame of said to be encoded speech signal;

estimating a pitch for said frame;

determining a synthetic phase contour over said frame based on said pitch estimate and a pitch estimate for a preceding frame;

locating at least one pitch pulse position in said determined synthetic phase contour;

locating at least one pitch pulse position in said frame of said to be encoded speech based signal; and

modifying said to be encoded speech based signal in said frame such that the at least one pitch pulse position is shifted to the at least one pitch pulse position of said synthetic phase contour.

21. The coding module according to claim 20, wherein said speech coding is a parametric speech coding employing at least one parameter indicative of the phase of a to be encoded speech based signal.

22. The coding module according to claim 20, wherein said pre-processing comprises modifying a respective frame of said to be encoded speech based signal such that a phase contour of said pre-processed to be encoded speech based signal over said frame corresponds basically to a synthetic phase contour determined from pitch estimates for said to be encoded speech based signal.