Classification-Based Frame Loss Concealment for Audio Signals

• US 20080033718A1
• Filed: 04/13/2007
• Published: 02/07/2008
• Est. Priority Date: 08/03/2006
• Status: Active Grant

• Current Assignee: Avago Technologies International Sales Pte Limited (Broadcom, Inc.)
• Original Assignee: Broadcom Corporation (Broadcom, Inc.)
• Inventors: Chen, Juin-Hwey, Thyssen, Jes, Zopf, Robert W.
• Granted Patent: US 8,015,000 B2
• Time in Patent Office: Days
• US Class Current: 704/229
• CPC Class Codes: G10L 19/005 Correction of errors induced by the transmission channel, if related to the coding algorithm
• CPC Class Codes: G10L 25/78 Detection of presence or absence of voice signals switching of direction of transmission by voice frequency in two-way loud-speaking telephone systems H04M9/10

Abstract

An audio decoding system performs frame loss concealment (FLC) when portions of a bit stream representing an audio signal are lost within the context of a digital communication system. The audio decoding system employs two different FLC methods: one designed to perform well for music, and the other designed to perform well for speech. When a frame is deemed lost, the audio decoding system analyzes a previously-decoded audio signal corresponding to previously-decoded frames of an audio bit-stream. Based on the results of the analysis, the lost frame is classified as either speech or music. Using this classification, other signal analysis, and knowledge of the employed FLC methods, the audio decoding system selects the appropriate FLC method which then performs FLC on the lost frame.

Claims

1. A method for performing frame loss concealment (FLC) in an audio decoder, comprising:

performing a first analysis on a previously-decoded portion of an audio signal;

classifying a lost frame as either speech or music based on the results of the first analysis;

performing a second analysis on the previously-decoded portion of the audio signal; and

selecting either a first FLC technique or a second FLC technique for replacing the lost frame based on the classification and the results of the second analysis.

2. The method of claim 1, wherein selecting a first FLC technique comprises selecting an FLC technique designed for speech.

3. The method of claim 2, wherein selecting an FLC technique designed for speech comprises selecting a periodic waveform extrapolation (PWE) based FLC technique.

4. The method of claim 1, wherein selecting a second FLC technique comprises selecting an FLC technique designed for music.

5. The method of claim 4, wherein selecting an FLC technique designed for music comprises selecting a frame repeat FLC technique.

6. The method of claim 1, wherein performing the second analysis comprises using a feature set used in performing the first analysis.

7. The method of claim 1, further comprising modifying at least one of the first or second FLC techniques based on the results of the second analysis.

8. The method of claim 7, wherein modifying at least one of the first or second FLC techniques comprises:

using a pitch multiple in a periodic waveform extrapolation (PWE) based FLC technique.

9. The method of claim 7, wherein modifying at least one of the first or second FLC techniques comprises:

mixing a shaped noise signal with the output of a frame repeat FLC technique.

10. A system for performing frame loss concealment (FLC) in an audio decoder, comprising:

a signal classifier configured to perform a first analysis on a previously-decoded portion of an audio signal and to classify a lost frame as either speech or music based on the results of the first analysis; and

decision logic coupled to the signal classifier, the decision logic configured to perform a second analysis on the previously-decoded portion of the audio signal and to select either a first FLC technique or a second FLC technique for replacing the lost frame based on the classification and the results of the second analysis.

11. The system of claim 10, wherein the first FLC technique is an FLC technique designed for speech.

12. The system of claim 11, wherein the FLC technique designed for speech is a periodic waveform extrapolation (PWE) based FLC technique.

13. The system of claim 10, wherein the second FLC technique is an FLC technique designed for music.

14. The system of claim 13, wherein the FLC technique designed for music is a frame repeat FLC technique.

15. The system of claim 10, wherein the decision logic is configured to perform the second analysis using a feature set used by the signal classifier in performing the first analysis.

16. The system of claim 10, wherein the decision logic is further configured to modify at least one of the first or second FLC techniques based on the results of the second analysis.

17. The system of claim 16, wherein the decision logic is configured to modify at least one of the first or second FLC techniques by using a pitch multiple in a periodic waveform extrapolation (PWE) based FLC technique.

18. The system of claim 16, wherein the decision logic is configured to modify at least one of the first or second FLC techniques by mixing a shaped noise signal with the output of a frame repeat FLC technique.

19. A method for performing frame loss concealment in an audio decoder, comprising:

(a) generating an extrapolated signal comprising a plurality of audio samples, wherein generating each sample of the extrapolated signal comprises;

(i) extrapolating an audio sample based on a previously-received frame of an audio signal and a pitch period; and

(ii) simultaneously with the extrapolation, overlap-adding a sample from an audio fade-out signal provided by the decoder; and

(b) using the extrapolated signal to produce a replacement frame.

20. The method of claim 19, further comprising:

determining the pitch period.

21. The method of claim 20, wherein determining the pitch period comprises:

deriving a set of candidate pitch periods based on an estimated pitch period;

generating a plurality of extrapolated signals, wherein each of the plurality of extrapolated signals is generated based on a previously-received frame of the audio signal and a corresponding one of the candidate pitch periods;

correlating each of the plurality of extrapolated signals with the audio fade-out signal;

selecting one of the plurality of the extrapolated signals based on the correlation; and

identifying the candidate pitch period associated with the selected one of the plurality of extrapolated signals as the pitch period.

22. A system for performing frame loss concealment in an audio decoder, comprising:

(a) first logic configured to generate an extrapolated signal comprising a plurality of audio samples, wherein generating each sample of the extrapolated signal comprises extrapolating an audio sample based on a previously-received frame of an audio signal and a pitch period and simultaneously with the extrapolation, overlap-adding a sample from an audio fade-out signal provided by the decoder; and

(b) second logic configured to use the extrapolated signal to produce a replacement frame.

23. The system of claim 22, further comprising:

third logic configured to determine the pitch period.

24. The system of claim 22, wherein the third logic comprises logic configured to derive a set of candidate pitch periods based on an estimated pitch period, to generate a plurality of extrapolated signals, wherein each of the plurality of extrapolated signals is generated based on a previously-received frame of the audio signal and a corresponding one of the candidate pitch periods, to correlate each of the plurality of extrapolated signals with the audio fade-out signal, to select one of the plurality of the extrapolated signals based on the correlation, and to identify the candidate pitch period associated with the selected one of the plurality of extrapolated signals as the pitch period.