Postfilter For Layered Codecs

• US 20100063801A1
• Filed: 12/14/2007
• Published: 03/11/2010
• Est. Priority Date: 03/02/2007
• Status: Active Grant

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Bruhn, Stefan
• Granted Patent: US 8,571,852 B2
• Time in Patent Office: Days
• US Class Current: 704/201
• CPC Class Codes: G10L 19/26 Pre-filtering or post-filtering

Abstract

A scalable decoder device (50) for signals representing audio comprises a primary decoder (21) connected to an input (40). The primary decoder (21) is arranged to provide a primary decoded signal (23) based on received parameters (4). A primary postfilter (31) is connected to the primary decoder (23) to provide a primary postfiltered signal (32). A secondary enhancement decoder (45) is connected to the input (40) and arranged to provide a secondary decoded enhancement signal (44). The device further comprises a combiner arrangement (55), arranged for combining the primary postfiltered signal (32) and a signal (53) based on the secondary decoded enhancement signal (44) into an output signal (6) to be provided at an output (6). The combining is made with an adaptable strength relation between contributions from the two signals. A method for decoding coded signals representing audio operates in analogy with the scalable decoder device (50).

Claims

1. Decoder device for signals representing audio or speech, comprising:

an input for parameters of coded signals;

a primary decoder connected to said input, arranged to provide a primary decoded signal based on said parameters;

a primary postfilter connected to an output of said primary decoder and arranged to provide a primary posffiltered signal;

secondary decoder connected to said input in addition to said primary decoder, said secondary decoder being arranged to provide a secondary decoded signal based on said parameters, said secondary decoded signal being different from said primary decoded signal;

a combiner arrangement, arranged for combining said primary posffiltered signal and a signal based on said secondary decoded signal into an output signal;

said output signal being a weighted combination of said primary postfiltered signal and said signal based on said secondary decoded signal; and

an output for said output signal, connected to said combiner arrangement.

2. The decoder device according to claim 1, wherein said combiner arrangement is arranged for adapting said weighted combination.

3. The decoder device according to claim 2, wherein said combiner arrangement comprises means for detecting signal properties and wherein said adapting is performed in response to said signal properties.

4. The decoder device according to claim 3, wherein said means for detecting signal properties is arranged to detect similarities between said primary decoded signal and said secondary decoded signal in a considered low-band.

5. The decoder device according to claim 3, wherein said means for detecting signal properties is arranged to detect any availability of a partial received bit stream rendering the secondary decoded signal different from the primary decoded signal.

6. The decoder device according to claim 1, wherein said primary postfilter is a long-delay postfilter utilizing a delay difference between said primary decoded signal and said secondary decoded signal.

7. The decoder device according to claim 1, wherein said secondary decoder is a secondary reconstruction decoder, in turn comprising a secondary enhancement decoder, and being further connected to an output of said primary decoder;

said secondary enhancement decoder being arranged to provide a secondary decoded enhancement signal based on said parameters; and

said secondary reconstruction decoder being arranged to provide a secondary decoded reconstruction signal based on said secondary decoded enhancement signal and said primary decoded signal.

8. The decoder device according to claim 7, wherein said signal based on said secondary decoded signal is said secondary decoded reconstruction signal.

9. The decoder device according to claim 7, further comprising a secondary postfilter connected to an output of said secondary reconstruction decoder and arranged to provide a secondary postfiltered signal, whereby said signal based on said secondary decoded signal is said secondary postfiltered signal.

10. The decoder device according to claim 1, wherein said combiner arrangement further comprises means for extracting a primary postfilter enhancement signal,

whereby said combiner arrangement is arranged for combining said primary postfilter enhancement signal and an enhancement signal based on said secondary decoded signal into a combined enhancement signal;

said combined enhancement signal being a weighted combination of said primary postfilter enhancement signal and said enhancement signal based on said secondary decoded signal, and

said combiner arrangement further comprises means for adding a signal based on said combined enhancement signal to a signal based on said primary decoded signal, to provide said output signal.

11. The decoder device according to claim 10, wherein said combiner arrangement further comprises one of a low-pass filter and a band-pass filter, filtering said combined enhancement signal into a filtered signal, being used as said signal based on said combined enhancement signal.

12. The decoder device according to claim 10, wherein

said secondary decoder is a secondary enhancement decoder;

said secondary enhancement decoder being arranged to provide a secondary decoded enhancement signal based on said parameters.

13. The decoder device according to claim 12, wherein

said enhancement signal based on said secondary decoded signal is said secondary decoded enhancement signal, and

said signal based on said primary decoded signal is a delayed version of said primary decoded signal.

14. The decoder device according to claim 12, further comprising a secondary postfilter connected to an output of said secondary enhancement decoder,

whereby said enhancement signal based on said secondary decoded signal is an output signal from said secondary postfilter, and wherein

said signal based on said primary decoded signal is a delayed version of said primary decoded signal.

15. The decoder device according to claim 10, wherein said secondary decoder is a secondary reconstruction decoder, in turn comprising a secondary enhancement decoder, and being further connected to an output of said primary decoder;

said secondary enhancement decoder being arranged to provide a secondary decoded enhancement signal based on said parameters;

said secondary reconstruction decoder being arranged to provide a secondary decoded reconstruction signal based on said secondary decoded enhancement signal and said primary decoded signal; and

a secondary postfilter connected to an output of said secondary decoder and arranged to provide a secondary postfiltered signal.

16. The decoder device according to claim 15, wherein

said combiner arrangement further comprises means for extracting a secondary postfilter enhancement signal to be used as said enhancement signal based on said secondary decoded signal, and

said signal based on said primary decoded signal is said secondary decoded reconstruction signal.

17. The decoder device according to claim 15, wherein

said combiner arrangement further comprises means for extracting said enhancement signal based on said secondary decoded signal as a difference between said secondary postfiltered signal and a delayed version of said primary decoded signal, and

said signal based on said primary decoded signal is a delayed version of said primary decoded signal.

18. The decoder device according to claim 1, wherein decoder device is a scalable decoder device.

19. Method of decoding coded signals representing audio or speech, comprising:

receiving parameters of a coded signal;

primary decoding of said parameters into a primary decoded signal;

primary postfiltering of said primary decoded signal into a primary postfiltered signal;

secondary decoding of said parameters into a secondary decoded signal, said secondary decoding being performed in addition to said primary decoding, said secondary decoded signal being different from said primary decoded signal;

combining said primary postmtered signal and a signal based on said secondary decoded signal into an output signal;

said output signal being a weighted combination of said primary postfiltered signal and said signal based on said secondary decoded signal; and

outputting said output signal.

20. The method according to claim 19, wherein said step of combining comprises adapting said weighted combination.

21. The method according to claim 20, wherein said step of combining comprises detecting of signal properties and wherein said adapting is performed in response to said detected signal properties.

22. The method according to claim 21, wherein said detecting comprises detecting of similarities between said primary decoded signal and said secondary decoded signal in a considered low-band.

23. The method according to claim 21, wherein said detecting comprises detecting of any availability of a partial received bit stream rendering the secondary decoded signal different from the primary decoded signal.

24. The method according to claim 19, wherein said step of primary postfiltering utilizes a delay difference between said primary decoded signal and said secondary decoded signal.

25. The method according to claim 19, wherein said step of secondary decoding comprises the step of secondary enhancement decoding of said parameters into a secondary decoded enhancement signal and the step of reconstructing a secondary decoded reconstruction signal to be used as said secondary decoded signal, based on said secondary decoded enhancement signal and said primary decoded signal.

26. The method according to claim 25, wherein said signal based on said secondary decoded signal is said secondary decoded reconstruction signal.

27. The method according to claim 25, comprising the further step of secondary postfiltering said secondary decoded reconstruction signal into a secondary posffiltered signal, whereby said secondary posffiltered signal is used as said signal based on said secondary decoded signal.

28. The method according to claim 19, wherein said step of combining comprises:

extracting a primary postfilter enhancement signal;

combining said primary postfilter enhancement signal and an enhancement signal based on said secondary decoded signal into a combined enhancement signal;

said combined enhancement signal being a weighted combination of said primary postfilter enhancement signal and said enhancement signal based on said secondary decoded signal; and

adding a signal based on said combined enhancement signal to a signal based on said primary decoded signal, to provide said output signal.

29. The method according to claim 28, wherein said step of combining further comprises at least one of low-pass filtering and a band-pass filtering of said combined enhancement signal into a filtered signal to be used as said signal based on said combined enhancement signal.

30. The method according to claim 28, wherein said step of secondary decoding comprises the step of secondary enhancement decoding of said parameters into a secondary decoded enhancement signal to be used as said secondary decoded signal.

31. The method according to claim 30, comprising the further step of delaying said primary decoded signal;

whereby said secondary decoded enhancement signal is used as said enhancement signal based on said secondary decoded signal, and

said delayed version of said primary decoded signal is used as said signal based on said primary decoded signal.

32. The method according to claim 30, comprising the further steps of:

delaying said primary decoded signal; and

secondary postfiltering said secondary decoded enhancement signal into a secondary postfiltered enhancement signal;

whereby said secondary postfiltered enhancement signal is used as said enhancement signal based on said secondary decoded enhancement signal, and

said delayed version of said primary decoded signal is used as said signal based on said primary decoded signal.

33. The method according to claim 28, wherein said step of secondary decoding comprises the step of secondary enhancement decoding of said parameters into a secondary decoded enhancement signal and the step of reconstructing a secondary decoded reconstruction signal to be used as said secondary decoded signal, based on said secondary decoded enhancement signal and said primary decoded signal;

said method comprising the further steps of;

secondary postfiltering said secondary decoded signal into a secondary postfiltered signal.

34. The method according to claim 33, wherein said step of combining comprises:

extracting of a secondary postfilter enhancement signal to be used as said enhancement signal based on said secondary decoded signal; and

said secondary decoded reconstruction signal is used as said signal based on said primary decoded signal.

35. The method according to claim 33, comprising the further step of:

delaying said primary decoded signal; and

wherein said step of combining comprises;

extracting said enhancement signal based on said secondary decoded signal as a difference between said secondary postfiltered signal and said delayed version of said primary decoded signal, and

whereby said delayed version of said primary decoded signal is used as said signal based on said primary decoded signal.

36. The method according to claim 19, wherein said parameters are scalable encoder parameters.