PACKET LOSS CONCEALMENT FOR SUB-BAND CODECS

• US 20100125454A1
• Filed: 11/06/2009
• Published: 05/20/2010
• Est. Priority Date: 11/14/2008
• Status: Active Grant

• Current Assignee: Avago Technologies International Sales Pte Limited (Broadcom, Inc.)
• Original Assignee: Broadcom Corporation (Broadcom, Inc.)
• Inventors: Pilati, Laurent, Zopf, Robert W.
• Granted Patent: US 8,706,479 B2
• Time in Patent Office: Days
• US Class Current: 704/219
• 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

Abstract

Packet loss concealment systems and methods are described that may be used in conjunction with a Bluetooth® Low-Complexity Sub-band Coding (LC-SBC) codec or other sub-band codecs, including but not limited to an MPEG-1 Audio Layer 3 (MP3) codec, an Advanced Audio Coding (AAC) codec, and a Dolby AC-3 codec.

Claims

1. A method for performing packet loss concealment (PLC) in a sub-band codec, comprising:

receiving a plurality of sub-band signals generated by decoding an encoded audio signal; and

responsive to determining that at least one frame of the encoded audio signal is lost;

applying a PLC algorithm to each sub-band signal to generate a plurality of PLC output signals;

combining the PLC output signals to generate a full-band output audio signal; and

storing at least a portion of each PLC output signal in a corresponding buffer for use in performing subsequent synthesis filtering operations.

2. The method of claim 1, wherein the sub-band codec is one of a Bluetooth®

Low-Complexity Sub-band Coding (LC-SBC) codec, an MPEG-1 Audio Layer 3 (MP3) codec, an Advanced Audio Coding (AAC) codec or a Dolby AC-3 codec.

3. The method of claim 1, wherein applying the PLC algorithm to each sub-band signal to generate the plurality of PLC output signals comprises:

calculating and maximizing a correlation between previously-received segments of each sub-band signal to identify a lag associated with each sub-band signal; and

extrapolating each sub-band signal based on the lag associated therewith.

4. A system, comprising:

decoding logic configured to generate a plurality of sub-band signals by decoding an encoded audio signal;

a plurality of packet loss concealment (PLC) modules, each of which is configured to apply a PLC algorithm to a corresponding sub-band signal to generate a PLC output signal;

a plurality ofsub-band signal generators, each of which is configured to select a corresponding sub-band signal or a corresponding PLC output signal; and

a synthesis filter bank configured to combine the signals selected by the plurality of sub-band signal generators to generate a full-band output audio signal.

5. The system of claim 4, wherein each of the sub-band signal generators is configured to select a corresponding sub-band signal or a corresponding PLC output signal based on a state of a bad frame indicator.

6. A method for performing packet loss concealment (PLC) in a sub-band codec, comprising:

receiving a plurality of sub-band signals generated by decoding an encoded audio signal;

combining the sub-band signals to generate a full-band audio signal; and

responsive to determining that a frame of the encoded audio signal is lost;

applying a PLC algorithm to the full-band audio signal to generate a PLC output signal; and

generating an output audio signal based on the PLC output signal, wherein generating the output audio signal based on the PLC output signal comprises processing the PLC output signal in an analysis filter bank to produce a plurality of re-encoded sub-band signals and combining the re-encoded sub-band signals to generate the output audio signal.

7. The method of claim 6, wherein the sub-band codec is one of a Bluetooth®

Low-Complexity Sub-band Coding (LC-SBC) codec, an MPEG-1 Audio Layer 3 (MP3) codec, an Advanced Audio Coding (AAC) codec or a Dolby AC-3 codec.

8. The method of claim 6, wherein applying a PLC algorithm to the full-band audio signal includes applying periodic waveform extrapolation to the full-band audio signal.

9. The method of claim 6, further comprising:

responsive to determining that a frame of the encoded audio signal represents a first good frame after a period of packet loss;

generating the output audio signal by combining a segment of the PLC output signal and a segment of a full-band audio signal generated by decoding the first good frame.

10. A method for performing packet loss concealment (PLC) in a sub-band codec, comprising:

receiving a plurality of sub-band signals generated by decoding an encoded audio signal;

combining the sub-band signals in a synthesis filter bank to generate a full-band audio signal; and

responsive to determining that a frame of the encoded audio signal is lost;

applying a PLC algorithm to the full-band audio signal to generate a PLC output signal; and

generating an output audio signal based on the PLC output signal, wherein generating the output audio signal based on the PLC output signal comprises combining a segment of a signal representative of a zero-input response of the synthesis filter bank with a segment of the PLC output signal responsive to determining that the lost frame comprises a first lost frame in a frame loss period.

11. The method of claim 10, wherein combining a segment of the signal representative of the zero-input response of the synthesis filter bank with a segment of the PLC output signal comprises:

providing the segment of the signal representative of the zero-input response of the synthesis filter bank as a segment of the output audio signal.

12. The method of claim 10, wherein generating the output audio signal based on the PLC output signal further comprises:

overlap-adding a segment of a signal representative of the ringing of a short-term prediction filter and a long-term prediction filter with the segment of the PLC output signal.

13. The method of claim 10, further comprising:

responsive to determining that a frame of the encoded audio signal is a first good frame after a period of frame loss;

generating the output audio signal by combining a segment of the PLC output signal with a segment of a signal representative of a zero-state response of the synthesis filter bank.

14. The method of claim 13, wherein combining the segment of the PLC output signal with a segment of the signal representative of the zero-state response of the synthesis filter bank comprises:

combining the segment of the PLC output signal with the segment of the signal representative of the zero-state response of the synthesis filter bank at a time at which a desired level of convergence has been achieved between the signal representative of the zero-state response of the synthesis filter bank and a full-band audio signal that would have been generated in the absence of frame loss.

15. A system, comprising:

decoding logic configured to generate a plurality of sub-band signals by decoding an encoded audio signal;

a synthesis filter bank configured to combine the sub-band signals to generate a full-band audio signal;

a packet loss concealment (PLC) module configured to apply a PLC algorithm to the full-band audio signal to generate a PLC output signal responsive to determining that a frame of the encoded audio signal is lost and to generate a frame of an output audio signal by combining a segment of a signal representative of a zero-input response of the synthesis filter bank with a segment of the PLC output signal responsive to determining that the lost frame comprises a first lost frame in a frame loss period.

16. The system of claim 15, wherein the PLC module is configured to generate the frame of the output audio signal by providing the segment of the signal representative of the zero-input response of the synthesis filter bank as a segment of the frame of the output audio signal.

17. The system of claim 15, wherein the PLC module is further configured to generate the frame of the output audio signal by overlap-adding a segment of a signal representative of the ringing of a short-term prediction filter and a long-term prediction filter with the segment of the PLC output signal.

18. The system of claim 15, wherein the PLC module is further configured to generate a frame of the output audio signal by combining a segment of the PLC output signal with a segment of a signal representative of a zero-state response of the synthesis filter bank responsive to determining that a frame of the encoded audio signal is a first good frame after a period of frame loss.

19. A system, comprising:

a synthesis filter bank configured to combine a plurality of sub-band signals to generate a full-band output audio signal;

a packet loss concealment (PLC) module configured to apply a PLC algorithm to the full-band output audio signal to generate a PLC output signal;

an analysis filter bank configured to decompose the PLC output signal into a plurality of re-encoded sub-band signals;

logic configured to generate a plurality of decoded sub-band signals by decoding an encoded audio signal; and

a plurality of sub-band signal generators, each of which is configured to select a corresponding decoded sub-band signal or a corresponding re-encoded sub-band signal for provision to the synthesis filter bank.

20. The system of claim 19, wherein each sub-band signal generator is configured to select a corresponding decoded sub-band signal or a corresponding re-encoded sub-band signal for provision to the synthesis filter bank based on a state of a bad frame indicator.