Packet loss concealment for sub-band codecs
View Patent ↗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.
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;
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 a full-band output audio signal based on the PLC output signal, wherein generating the full-band 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 full-band output audio signal, wherein at least one of the receiving, combining, applying and generating steps is performed by a processor or an integrated circuit.
2. The method of claim 1 , wherein the sub-band codec is one of a Low-Complexity Sub-band Coding (LC-SBC) codec that is implemented in accordance with a Bluetooth protocol, 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 a PLC algorithm to the full-band audio signal includes applying periodic waveform extrapolation to the full-band audio signal.
4. The method of claim 1 , 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.
5. 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 between a corresponding decoded sub-band signal and a corresponding re-encoded sub-band signal for provision to the synthesis filter bank.
6. The system of claim 5 , wherein each sub-band signal generator is configured to select between a corresponding decoded sub-band signal and a corresponding re-encoded sub-band signal for provision to the synthesis filter bank based on a state of a bad frame indicator.
7. The system of claim 5 , wherein the PLC module is configured to apply the PLC algorithm to the full-band output audio signal by applying periodic waveform extrapolation to the full-band output audio signal.
8. The method of claim 1 , wherein the re-encoded sub-band signals are un-quantized sub-band signals.
9. The method of claim 1 , further comprising:
responsive to determining that the frame of the encoded audio signal is not lost:
generating a full-band output audio signal based on the full-band audio signal.
10. The method of claim 4 , wherein combining the segment of the PLC output signal and the segment of the full-band audio signal generated by decoding the first good frame comprises overlap-adding the segment of the PLC output signal and the segment of the full-band audio signal generated by decoding the first good frame.
11. The system of claim 5 , wherein the plurality of re-encoded sub-band signals are a plurality of un-quantized sub-band signals.
12. The system of claim 5 , wherein each of the plurality of sub-band signal generators are configured to select the corresponding decoded sub-band signal for provision to the synthesis filter bank in response to a determination that a good frame of an encoded audio signal from which the plurality of sub-band signals are decoded is received.
13. The system of claim 12 , wherein each of the plurality of sub-band signal generators are configured to select the corresponding re-encoded sub-band signal for provision to the synthesis filter bank in response to a determination that a frame of the encoded audio signal is lost.
14. A computer readable storage device having computer program instructions embodied in said computer readable storage medium for enabling a processor to perform packet loss concealment (PLC) in a sub-band codec, the computer program instructions including instructions executable to perform operations 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 a full-band output audio signal based on the PLC output signal, wherein generating the full-band 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 full-band output audio signal.
15. The computer readable storage device of claim 14 , wherein the sub-band codec is one of a Low-Complexity Sub-band Coding (LC-SBC) codec that is implemented in accordance with a Bluetooth protocol, an MPEG-1 Audio Layer 3 (MP3) codec, an Advanced Audio Coding (AAC) codec or a Dolby AC-3 codec.
16. The computer readable storage device of claim 14 , wherein applying a PLC algorithm to the full-band audio signal includes applying periodic waveform extrapolation to the full-band audio signal.
17. The computer readable storage device of claim 14 , wherein the operations further comprise:
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.
18. The computer readable storage device of claim 14 , wherein the re-encoded sub-band signals are un-quantized sub-band signals.
19. The computer readable storage device of claim 14 , wherein the operations further comprise:
responsive to determining that the frame of the encoded audio signal is not lost:
generating a full-band output audio signal based on the full-band audio signal.
20. The computer readable storage device of claim 17 , wherein combining the segment of the PLC output signal and the segment of the full-band audio signal generated by decoding the first good frame comprises overlap-adding the segment of the PLC output signal and the segment of the full-band audio signal generated by decoding the first good frame.