Scalable hybrid auto coder for transient detection in advanced audio coding with spectral band replication

1. A method of reusing information in a low power scalable hybrid audio encoder, the method comprising:

determining, by a processor, a state of an advanced audio coding (AAC) transient flag;

performing spectral band replication (SBR) transient detection on at least two possible locations upon a determination that the AAC transient flag is equal to a first value;

performing SBR transient detection on a high frequency upon a determination that the AAC transient flag is equal to a second value; and

determining, by the processor, whether a transient exists.

2. The method of claim 1 , wherein upon a determination that a transient exists, a SBR flag is set to a third value.

3. The method of claim 1 , wherein upon a determination that a transient does not exist, a SBR flag is set to a fourth value.

4. The method of claim 1 , wherein information from at least one transient coding is reused by either a SBR coding module or a transform coding module.

5. The method of claim 4 , wherein the information from the at least one transform coding is reused in the SBR coding module.

6. The method of claim 1 , wherein a complexity of the hybrid coder is reduced by reusing transient detection information from a core transform coder in a parametric coder of a next frame.

7. The method of claim 6 , further comprising at least one of performing normal detection on an upper half of a frequency range in SBR and performing normal detection on two candidate positions as narrowed down by the AAC result.

8. The method of claim 7 , wherein SBR transient detection is performed in time domain by comparing an energy of a subblock with a sliding average of previous energies.

9. The method of claim 8 , wherein a transient is determined to exist when SBR transient detection produces a value that exceeds a predetermined constant.

10. A method of reusing information in a low power scalable hybrid audio encoder, the method comprising:

determining, by a processor, a state of an advanced audio coding (AAC) transient flag;

performing spectral band replication (SBR) transient detection on at least one location based upon an energy in a signal upon a determination that the AAC transient flag is equal to a first value;

performing SBR transient detection on a high frequency upon a determination that the AAC flag is equal to a second value; and

determining, by the processor, whether a transient exists.

11. The method of claim 10 , wherein upon a determination that a transient exists, a SBR flag is set to a third value.

12. The method of claim 10 , wherein upon a determination that a transient does not exist, a SBR flag is set to a fourth value.

13. The method of claim 10 , wherein information from at least one transient coding is reused by either a SBR coding module or a transform coding module.

14. The method of claim 13 , wherein the information from the at least one transform coding is reused in the SBR coding module.

15. The method of claim 14 , wherein a complexity of the hybrid coder is reduced by reusing transient detection information from a core transform coder in a parametric coder of a next frame.

16. The method of claim 15 , further comprising at least one of performing normal detection on an upper half of a frequency range in SBR and performing normal detection on two candidate positions as narrowed down by the AAC flag.

17. The method of claim 15 , wherein SBR transient detection is performed in time domain by comparing an energy of a subblock with a sliding average of previous energies.

18. The method of claim 17 , wherein a transient is determined to exists when SBR transient detection produces a value that exceeds a predetermined constant.

19. A system of reusing information in a low power scalable hybrid audio encoder, the system comprising:

a spectral band replication (SBR) coding module, using a processing system of a low power audio communication device, configured to determine a state of an advanced audio coding (AAC) transient flag and perform SBR transient detection on at least one location based upon an energy in a signal upon a determination that the AAC transient flag is equal to a first value;

a transform coding module using the processing system and configured to perform SBR transient detection on a high frequency upon a determination that the AAC transient flag is equal to a second value; and

a bitstream payload formatter configured to output data from the hybrid audio encoder.

20. The system of claim 19 , wherein a transient detector from the transform coding module is used in the SBR coding module.