AUDIO FRAME LOSS CONCEALMENT

• US 20150371642A1
• Filed: 01/22/2014
• Published: 12/24/2015
• Est. Priority Date: 02/05/2013
• Status: Active Grant

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: BRUHN, Stefan
• Granted Patent: US 9,847,086 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G10L 19/005 Correction of errors induced by the transmission channel, if related to the coding algorithm
• CPC Class Codes: G10L 19/02 using spectral analysis, e.g. transform vocoders or subband vocoders
• CPC Class Codes: G10L 25/69 for evaluating synthetic or decoded voice signals

Abstract

Concealing a lost audio frame of a received audio signal by performing a sinusoidal analysis of a part of a previously received or reconstructed audio signal, wherein the sinusoidal analysis involves identifying frequencies of sinusoidal components of the audio signal, applying a sinusoidal model on a segment of the previously received or reconstructed audio signal, wherein said segment is used as a prototype frame in order to create a substitution frame for a lost audio frame, and creating the substitution frame for the lost audio frame by time-evolving sinusoidal components of the prototype frame, up to the time instance of the lost audio frame, in response to the corresponding identified frequencies.

Claims

1. A method of concealing a lost audio frame of a received audio signal, the method comprising:

performing a sinusoidal analysis (81) of a part of a previously received or reconstructed audio signal, wherein the sinusoidal analysis involves identifying frequencies of sinusoidal components of the audio signal;

applying a sinusoidal model (82) on a segment of the previously received or reconstructed audio signal, wherein said segment is used as a prototype frame in order to create a substitution frame for a lost audio frame, and

creating the substitution frame (83) for the lost audio frame involving time-evolution of sinusoidal components of the prototype frame, up to the time instance of the lost audio frame, in response to the corresponding identified frequencies.

2. The method according to claim 1, wherein it is assumed that the audio signal is composed of a limited number of individual sinusoidal components.

3. The method according to any of claims 1-2, wherein the sinusoidal analysis is performed in a frequency domain.

4. The method according to claim 3, wherein the identifying of frequencies of sinusoidal components further involves identifying frequencies in the vicinity of the peaks of the spectrum related to a used frequency domain transform.

5. The method according to claim 3 or 4, wherein the identifying of frequencies of sinusoidal components is performed with higher resolution than the frequency resolution of the used frequency domain transform.

6. The method according to claim 5, wherein the identifying of frequencies of sinusoidal components further involves interpolation.

7. The method according to claim 6, wherein the interpolation is of parabolic type.

8. The method according to any of claims 1-7, further comprising extracting a prototype frame from an available previously received or reconstructed signal using a window function.

9. The method according to claim 8, further comprising transforming the extracted prototype frame into a frequency domain representation.

10. The method according to claim 9, further involving an approximation of the window function spectrum such that a substitution frame spectrum is composed of strictly non-overlapping portions of the approximated window function spectrum.

11. The method according to any of the claim 9 or 10, further comprising time-evolving sinusoidal components of a frequency spectrum of a prototype frame by advancing the phase of a sinusoidal component, in response to the frequency of this sinusoidal component and in response to the time difference between the lost audio frame and the prototype frame.

12. The method according to any of claims 9-11, further comprising changing a spectral coefficient of the prototype frame included in an interval M_k in the vicinity of a sinusoid k by a phase shift proportional to the sinusoidal frequency f_k and the time difference between the lost audio frame and the prototype frame.

13. The method according to any of claims 9-12, further comprising changing the phase of a spectral coefficient of the prototype frame not belonging to an identified sinusoid by a random phase.

14. The method according to any of claims 9-12, further comprising changing the phase of a spectral coefficient of the prototype frame not included in any of the intervals related to the vicinity of the identified sinusoids by a random value.

15. The method according to any of the claims 9-14, further involving an inverse frequency domain transform of the frequency spectrum of the prototype frame.

18. The decoder according to claim 15 or 16, wherein the identifying of frequencies of sinusoidal components of the audio signal further comprises a parabolic interpolation.

19. The decoder according to any of the claims 15-18, further configured to extract a prototype frame from an available previously received or reconstructed signal using a window function.

20. The decoder according to claim 19, further configured to transform the extracted prototype frame into a frequency domain.

21. The decoder according to claim 20, further configured to time-evolve sinusoidal components of a frequency spectrum of a prototype frame by advancing the phase of the sinusoidal components, in response to the frequency of each sinusoidal component and in response to the time difference between the lost audio frame and the prototype frame.

22. The decoder according to claim 21, further configured to create the substitution frame by performing an inverse frequency transform of the frequency spectrum.

25. Computer program (91) comprising instructions which when run by a processor causes the processor to perform a method according to any of the claims 1-15.

26. A computer program product (9) comprising a computer readable medium storing a computer program (91) according to claim 25.

16. A decoder (1) configured to conceal a lost audio frame of a received audio signal, the decoder comprising a processor (11) and memory (12), the memory containing instructions executable by the processor (11), whereby the decoder (1) is configured to:

perform a sinusoidal analysis of a part of a previously received or reconstructed audio signal, wherein the sinusoidal analysis involves identifying frequencies of sinusoidal components of the audio signal;

apply a sinusoidal model on a segment of the previously received or reconstructed audio signal, wherein said segment is used as a prototype frame in order to create a substitution frame for a lost audio frame, and

create the substitution frame for the lost audio frame by time-evolving sinusoidal components of the prototype frame, up to the time instance of the lost audio frame, in response to the corresponding identified frequencies.

17. The decoder according to claim 16, wherein the applied sinusoidal model assumes that the audio signal is composed of a limited number of individual sinusoidal components.

24. A receiver comprising a decoder according to any of the claims 16-23.

23. A decoder (1) configured to conceal a lost audio frame of a received audio signal, the decoder comprising an input unit configured to receive an encoded audio signal, and a frame loss concealment unit (13) comprising:

means (14) for performing a sinusoidal analysis of a part of a previously received or reconstructed audio signal, wherein the sinusoidal analysis involves identifying frequencies of sinusoidal components of the audio signal;

means (15) for applying a sinusoidal model on a segment of the previously received or reconstructed audio signal, wherein said segment is used as a prototype frame in order to create a substitution frame for a lost audio frame, and

means (16) for creating the substitution frame for the lost audio frame by time-evolving sinusoidal components of the prototype frame, up to the time instance of the lost audio frame, in response to the corresponding identified frequencies.