CONSTRAINED AND CONTROLLED DECODING AFTER PACKET LOSS

• US 20090232228A1
• Filed: 05/29/2009
• Published: 09/17/2009
• Est. Priority Date: 08/15/2006
• Status: Active Grant

• Current Assignee: Avago Technologies International Sales Pte Limited (Broadcom, Inc.)
• Original Assignee: Broadcom Corporation (Broadcom, Inc.)
• Inventors: Thyssen, Jes
• Granted Patent: US 8,041,562 B2
• Time in Patent Office: Days
• US Class Current: 375/242
• CPC Class Codes: G10L 19/005 Correction of errors induced by the transmission channel, if related to the coding algorithm
• CPC Class Codes: G10L 19/0204 using subband decomposition
• CPC Class Codes: G10L 19/04 using predictive techniques

Abstract

A technique is described herein for reducing audible artifacts in an audio output signal generated by decoding a received frame in a series of frames representing an encoded audio signal in a predictive coding system. In accordance with the technique, it is determined if the received frame is one of a predefined number of received frames that follow a lost frame in the series of the frames. Responsive to determining that the received frame is one of the predefined number of received frames, at least one parameter or signal associated with the decoding of the received frame is altered from a state associated with normal decoding. The received frame is then decoded in accordance with the at least one parameter or signal to generate a decoded audio signal. The audio output signal is then generated based on the decoded audio signal.

Claims

1. A method for reducing high-frequency distortion in an output audio signal produced by a decoder in conjunction with frame erasure concealment functionality, comprising:

decoding a bit stream corresponding to a frame of an encoded audio signal in a first sub-band decoder to produce a first sub-band decoder output signal;

high-pass filtering the first sub-band decoder output signal to produce a first sub-band reconstructed output signal responsive to at least determining that the frame of the encoded audio signal is one of a predefined number of good frames following an erased frame in the encoded audio signal;

combining the first sub-band reconstructed output signal with a second sub-band reconstructed output signal to produce the output audio signal.

2. The method of claim 1, wherein the decoder comprises a G.722 decoder;

wherein decoding the bit stream corresponding to the frame of the encoded audio signal in the first sub-band decoder to produce a first sub-band decoder output signal comprises decoding the bit stream in a high-band Adaptive Differential Pulse Code Modulation (ADPCM) decoder to produce a high-band ADPCM decoder output signal;

wherein high-pass filtering the first sub-band decoder output signal to produce a first sub-band reconstructed output signal comprises high-pass filtering the high-band ADPCM decoder output signal to produce a high-band reconstructed output signal; and

wherein combining the first sub-band reconstructed output signal with the second sub-band reconstructed output signal comprises combining the high-band reconstructed output signal and a low-band reconstructed output signal.

3. The method of claim 2, wherein high-pass filtering the high-band ADPCM decoder output signal to produce the high-band reconstructed output signal comprises passing the high-band ADPCM decoder output signal through a first-order pole/zero filter.

4. The method of claim 3, wherein passing the high-band ADPCM decoder output signal through the first-order pole/zero filter comprises:

passing the high-band ADPCM decoder output signal through a filter having the form

r_H,HP(n)=0.97└

r_H(n)−

r_H(n−

1)+r_H,HP(n−

1)┘

wherein r_H(n) represents the high-band ADPCM decoder output signal and r_H,HP(n) represents the high-band reconstructed output signal.

5. The method of claim 2, wherein high-pass filtering the high-band ADPCM decoder output signal comprises removing a DC offset from the high-band ADPCM decoder output signal.

6. The method of claim 1, wherein the predefined number of good frames following the erased frame is associated with a predetermined time period following the erased frame.

7. The method of claim 6, wherein the predetermined time period following the erased frame is 40 milliseconds.

8. The method of claim 2, further comprising:

providing the reconstructed high-band output signal as an input to the high-band ADPCM decoder for use in decoding a bit stream corresponding to a subsequent frame of the encoded audio signal.

9. A decoder having integrated frame erasure concealment functionality, comprising:

a first sub-band decoder that decodes a bit stream corresponding to a frame of an encoded audio signal to produce a first sub-band decoder output signal;

control logic that high-pass filters the first sub-band decoder output signal to produce a reconstructed first sub-band output signal responsive to at least determining that the frame of the encoded audio signal is one of a predefined number of good frames following an erased frame in the encoded audio signal; and

a quadrature mirror filter (QMF) synthesis filter bank that combines the reconstructed first sub-band output signal with a reconstructed second sub-band output signal to produce an output audio signal.

10. The decoder having integrated frame erasure concealment functionality of claim 9, wherein:

the first sub-band decoder comprises a high-band Adaptive Differential Pulse Code Modulation (ADPCM) decoder that decodes the bit stream corresponding to the frame of the encoded audio signal to produce a high-band ADPCM decoder output signal;

the control logic high-pass filters the high-band ADPCM decoder output signal to produce a reconstructed high-band output signal; and

the QMF synthesis filter bank combines the reconstructed high-band output signal with a reconstructed low-band output signal to produce the output audio signal.

11. The decoder having integrated frame erasure concealment functionality of claim 10, wherein the control logic high-pass filters the high-band ADPCM decoder output signal by passing the high-band ADPCM decoder output signal through a first-order pole/zero filter.

12. The decoder having integrated frame erasure concealment functionality of claim 11, wherein the control logic passes the high-band ADPCM decoder output signal through a filter having the form

r_H,HP(n)=0.97└

r_H(n)−

r_H(n−

1)+r_H,HP(n−

1)┘

wherein r_H (n) represents the high-band ADPCM decoder output signal and r_H,HP(n) represents the high-band reconstructed output signal.

13. The decoder having integrated frame erasure concealment functionality of claim 10, wherein the high-pass filtering of the high-band ADPCM decoder output signal by the control logic removes a DC offset from the high-band ADPCM decoder output signal.

14. The decoder having integrated frame erasure concealment functionality of claim 9, wherein the predefined number of good frames following the erased frame is associated with a predetermined time period following the erased frame.

15. The decoder having integrated frame erasure concealment functionality of claim 14, wherein the predetermined time period following the erased frame is 40 milliseconds.

16. The decoder having integrated frame erasure concealment functionality of claim 10, wherein the control logic provides the reconstructed high-band output signal as an input to the high-band ADPCM decoder for use in decoding a bit stream corresponding to a subsequent frame of the encoded audio signal.

17. A computer program product comprising a computer-readable medium having computer program logic recorded thereon for enabling a processor to reduce high-frequency distortion in an output audio signal produced by the execution of a decoding process in conjunction with frame erasure concealment, the computer program logic comprising:

first means for enabling the processor to perform first sub-band decoding of a bit stream corresponding to a frame of an encoded audio signal to produce a first sub-band decoder output signal;

second means for enabling the processor to high-pass filter the first sub-band decoder output signal to produce a first sub-band reconstructed output signal responsive to at least determining that the frame of the encoded audio signal is one of a predefined number of good frames following an erased frame in the encoded audio signal; and

third means for enabling the processor to combine the first sub-band reconstructed output signal with a second sub-band reconstructed output signal to produce the output audio signal.

18. The computer program product of claim 17, wherein:

the first means comprises means for enabling the processor to perform high-band Adaptive Differential Pulse Code Modulation (ADPCM) decoding of the bit stream corresponding to the frame of the encoded audio signal to produce a high-band ADPCM decoder output signal;

the second means comprises means for enabling the processor to high-pass filter the high-band ADPCM decoder output signal to produce a high-band reconstructed output signal; and

the third means comprises means for enabling the processor to combine the high-band reconstructed output signal with a low-band reconstructed output signal to produce the output audio signal.

19. The computer program product of claim 18, wherein the second means comprises means for enabling the processor to pass the high-band ADPCM decoder output signal through a first-order pole/zero filter.

21. The computer program product of claim 18, wherein the second means comprises means for enabling the processor to remove a DC offset from the high-band ADPCM decoder output signal.

22. The computer program product of claim 17, wherein the predefined number of good frames following the erased frame is associated with a predetermined time period following the erased frame.

23. The computer program product of claim 22, wherein the predetermined time period following the erased frame is 40 milliseconds.

24. The computer program product of claim 18, wherein the second means further comprises:

means for enabling the processor to provide the reconstructed high-band output signal as an input to the high-band ADPCM decoder for use in decoding a bit stream corresponding to a subsequent frame of the encoded audio signal.

20. The computer program product of clam 19, wherein the means for enabling the processor to pass the high-band ADPCM decoder output signal through the first-order pole/zero filter comprises means for enabling the processor to pass the high-band ADPCM decoder output signal through a filter having the form

r_H,HP(n)=0.97└

r_H(n)−

r_H(n−

1)+r_H,HP(n−

1)┘

wherein r_H (n) represents the high-band ADPCM decoder output signal and r_H,HP(n) represents the high-band reconstructed output signal.