Method for adaptive codebook pitch-lag computation in audio transcoders

• US 20040002855A1
• Filed: 03/12/2003
• Published: 01/01/2004
• Est. Priority Date: 03/12/2002
• Status: Active Grant

• Current Assignee: Onmobile Global Limited
• Original Assignee: Dilithium Networks
• Inventors: Ibrahim, Michael, Georgy, Sameh, Jabri, Marwan A., Wang, Jian Wei
• Granted Patent: US 7,260,524 B2
• Time in Patent Office: Days
• US Class Current: 704/219
• CPC Class Codes: G10L 19/09 Long term prediction, i.e. removing periodical redundancies, e.g. by using adaptive codebook or pitch predictor
• CPC Class Codes: G10L 19/173 Transcoding, i.e. converting between two coded representations avoiding cascaded coding-decoding

Abstract

An apparatus for processing adaptive codebook pitch lag from one CELP based standard to another CELP based standard. The apparatus has various modules that perform at least the functionality described herein. The apparatus includes a time-base subframe checker inspection module, which is adapted to associate one or more incoming subframes with an outgoing subframes of a destination codec. The apparatus also has a decision module coupled to the time-base subframe inspection module. The decision module is adapted to determine a desired pitch lag parameter from a plurality of pitch lag parameters among respective two or more incoming subframes. The apparatus has a pitch lag selection module coupled to the decision module. The pitch lag selection module is adapted to select the desired pitch lag parameter.

Claims

1. An apparatus for processing adaptive codebook pitch lag from one CELP based standard to another CELP based standard, comprising:

a time-base subframe interpolator, the time-based subframe inspection module being adapted to associate one or more incoming subframes with an outgoing subframes of a destination codec;

a decision module coupled to the time-base inspection module, the decision module being adapted to determine a desired pitch lag parameter from a plurality of pitch lag parameters among respective two or more incoming subframes; and

a pitch lag selection module coupled to the decision module, the decision module being adapted to select the desired pitch lag parameter.

2. The apparatus of claim 1 wherein the time-base subframe inspection module is a single module or multiple modules.

3. The apparatus of claim 1 wherein the desired pitch lag parameter is a pitch lag of an incoming subframe that has a maximum value of a criteria of pitch lag selection function associated with the two or more incoming subframes.

4. The apparatus of claim 1 wherein the desired pitch lag parameter is a pitch lag of an incoming subframe that has a weighted average or average value of a criteria of pitch lag selection function associated with the two or more incoming subframes.

5. The apparatus of claim 1 wherein the decision module is a single module or multiple modules.

6. The apparatus of claim 1 wherein the pitch lag selection module is a single module or multiple modules.

7. The apparatus of claim 1 wherein said one and another CELP based standard have either different subframe size or same subframe size CELP codecs.

8. The apparatus of claim 1, wherein said time-base subframe inspection module comprises:

an adaptive codebook buffer, the adaptive code book buffer being adapted to store a pitch lag, a pitch gain, and one or more samples of input sub-frames that wait for mapping into one or more destination subframes.

a discriminator coupled to the adaptive codebook buffer, the discriminator being adapted to determine whether the destination subframe is covered by multiple source subframes.

15. The apparatus according to claim 1 wherein the decision module calculates an energy of the adaptive codebook parameters in each subframe by the following equation:

16. The apparatus according to claim 1 wherein the decision module searching the desired value comprising a maximum value of the criterion by the following equation:

E_max=max(E₁,E₂. . . E_n)

wherein E_max is the maximum E among all sub-frames which are overlapped with the destination sub-frame m

9. A method for processing an adaptive codebook parameter pitch-lag from a source CELP based codec to a destination CELP standard codec, said method comprising:

storing in memory more than one adaptive codebook parameters of one or more respective subframes from a source codec;

deciding whether a destination subframe is wholly covered by one source subframe while the one or more sub-frames wait for mapping;

output a pitch lag of a source subframe if the destination subframe is wholly covered by the single source subframe or

output a pitch lag of a source subframe that has a desired value of a selection function based upon a criterion by a decision module if the destination subframe is covered by two or more source subframes.

10. A method as defined in claim 9, wherein the output of the pitch lag of a source subframe that has the desired value comprises a maximum value of the criterion by the decision module comprises:

searching the maximum value of the criterion by the decision module if the destination subframe is covered by more than one source subframe;

selecting the pitch lag of a subframe which has the maximum value of the criterion of selection function among all searched subframes; and

outputting the pitch lag of the selected subframe from the source codec.

11. The method of claim 9 wherein the desired pitch lag value is a pitch lag of an incoming subframe that has a maximum value of criterion.

12. The method of claim 9 wherein the desired pitch lag value is a pitch lag of an incoming subframe that has an averaged value or a weighted average value of criteria.

13. The method of claim 9 wherein the one or more subframes from the source codec comprises a first incoming subframe, the incoming subframe comprising an incoming edge and the destination subframe for the destination codec comprises a first outgoing subframe, the outgoing subframe comprises an outgoing edge;

wherein the incoming edge is aligned with the outgoing edge at a designated time.

14. A method as defined in claim 10, wherein the searching the desired value of the criterion by the decision module, comprises:

combining the adaptive codebook parameters of each subframe which covers the destination subframe;

computing a proportion of each subframe covering the destination subframe;

computing an energy of the adaptive codebook parameters in each subframe;

indexing the source subframe which has a maximum energy of the adaptive codebook parameters.

17. A computer based system for processing adaptive codebook pitch lag from one CELP based standard to another CELP based standard, comprising:

a. one or more codes directed to a time-base subframe inspection module, the time-base subframe inspection module being adapted to associate one or more incoming subframes with an outgoing subframe of a destination codec;

b. one or more codes directed to a decision module coupled to the time-base inspection module, the decision module being adapted to determine a desired pitch lag parameter from a plurality of pitch lag parameters among respective the two or more incoming subframes; and

c. one or more codes directed to a pitch lag selection module coupled to the decision module, the decision module being adapted to select the desired pitch lag parameter.

18. The system of claim 17 wherein the time-base subframe inspection module is a single module or multiple modules.

19. The system of claim 17 wherein the desired pitch lag parameter is a maximum pitch lag associated with the two or more incoming subframes.

20. The system of claim 17 wherein the desired pitch lag parameter is a pitch lag of an incoming subframe that has an weighted average or an average value of criteria associated with the two or more incoming subframes.

21. The system of claim 17 wherein the decision module is a single module or multiple modules.

22. The system of claim 17 wherein the pitch lag selection module is a single module or multiple modules.

23. The system of claim 17 wherein said one and another CELP based standard have either different subframe size or same subframe size CELP codecs.

24. The system of claim 17 wherein said time-base subframe inspection module comprises:

a. one or more codes directed to an adaptive codebook buffer, the adaptive code book buffer being adapted to store a pitch lag, a pitch gain, and one or more number of samples of input subframes that wait for mapping into one or more destination subframes.

b. one or more codes directed to a discriminator coupled to the adaptive codebook buffer, the discriminator being adapted to determine whether the destination subframe is covered by multiple source subframes.