System and method for concealment of data loss in digital audio transmission

• US 7,069,208 B2
• Filed: 01/24/2001
• Issued: 06/27/2006
• Est. Priority Date: 01/24/2001
• Status: Active Grant

• Current Assignee: Nokia Solutions and Networks US LLC (Nokia Corporation)
• Original Assignee: Nokia Corporation
• Inventors: Wang, Ye
• Primary Examiner(s): Ometz, David L.
• Assistant Examiner(s): Jackson, Jakieda R
• Application Number:
  US09/770,113
• Publication Number:
  US 20020133764A1
• Time in Patent Office: 1,980 Days
• Field of Search: 704/211, 704/503, 704/228, 725/36
• US Class Current: 704/211
• CPC Class Codes: G10H 1/0058 Transmission between separate instruments or between individual components of a musical system G10H1/0083 takes precedence
• CPC Class Codes: G10H 2240/061 MP3, i.e. MPEG-1 or MPEG-2 Audio Layer III, lossy audio compression
• CPC Class Codes: G10H 2240/185 Error prevention, detection or correction in files or streams for electrophonic musical instruments
• CPC Class Codes: G10H 2240/245 ISDN [Integrated Services Digital Network]
• CPC Class Codes: G10H 2240/251 Mobile telephone transmission, i.e. transmitting, accessing or controlling music data wirelessly via a wireless or mobile telephone receiver, analog or digital, e.g. DECT GSM, UMTS smartphone, PDA or palmtop used for musical purposes G10H2230/015; mobile ringtone G10H2230/021
• CPC Class Codes: G10H 2240/295 Packet switched network, e.g. token ring circuit-switched networks, e.g. traditional analog telephone transmission G10H2240/241
• CPC Class Codes: G10H 2240/305 Internet or TCP/IP protocol use for any electrophonic musical instrument data or musical parameter transmission purposes
• CPC Class Codes: G10L 19/005 Correction of errors induced by the transmission channel, if related to the coding algorithm
• CPC Class Codes: G10L 19/0212 using orthogonal transformation

Abstract

A system and method for the concealment of errors resulting from missing or corrupted data in the transmission of audio signals in compressed digital packet formats is disclosed. The system utilizes a circular FIFO buffer to store audio frames from the transmitted audio signal, and a beat detector, to identify the presence of beats in the audio signal. The error concealment method replaces erroneous audio frames with error-free audio frames by a process which takes into account the presence and location of the detected beats.

Claims

1. A method for concealing errors detected in an input digital audio bit stream, the audio bit stream configured as a series of frames, said method comprising the steps of:

detecting a first beat and a subsequent plurality of beats in the audio bit stream;

defining a first inter-beat interval extending between said first beat and a (k+1)^th subsequent beat;

storing at least a portion of the audio bit stream occurring within said first inter-beat interval;

detecting an erroneous audio segment occurring in a second inter-beat interval extending between said (k+1)^th beat and a (2k+1)^th subsequent beat; and

replacing at least a first part of said erroneous audio segment with a corresponding part of said stored audio bit stream portion, wherein the corresponding part is selected based on a time relationship between the first part and one of the (k+1)^th and (2k+1)^th beats.

2. A method as in claim 1 wherein ‘

k’

is an integer greater than or equal to 2.

3. A method as in claim 1 wherein said stored audio bit stream portion includes at least one frame positioned on at least one of said beats.

4. A method as in claim 1 wherein said step of detecting a first beat comprises a step of computing the variance of the audio bit stream using decoded IMDCT coefficients.

5. A method as in claim 1 wherein said step of detecting a first beat comprises a step of utilizing a window-switching pattern.

6. A method as in claim 1 wherein said step of detecting a first beat comprises a step of computing the envelope of the audio bit stream using decoded IMDCT coefficients.

7. A method as in claim 1 wherein said step of detecting a first beat comprises steps of computing the variance of the audio bit stream using decoded IMDCT coefficients and utilizing a window-switching pattern.

8. A method as in claim 1 wherein said step of storing at least a portion of the audio bit stream includes a step of storing said portion in a circular first-in first-out (FIFO) buffer.

9. A method as in claim 1 wherein the audio bit stream includes a music signal.

10. A method as in claim 1 wherein the erroneous audio segment is the result of at least one of a packet loss from an IP network and a burst error from a wireless channel.

11. A method as in claim 1 further comprising the step of replacing one beat with another beat from a preceding bar.

12. A method as in claim 1, wherein the first part has a time displacement τ

from one of the (k+1)^th and (2k+1)^th beats, and wherein the corresponding part is selected so as to have the same time displacement τ

from one of the first and (k+1)^th beats.

13. A method as in claim 1, further comprising:

determining a confidence score, the confidence score being a percentage of correct beat detection within an observation window; and

discontinuing said replacing step when the confidence score is below a threshold value.

14. A method as in claim 1, further comprising estimating an inter-beat interval according to the formula

IBI_i=IBI_i-1* (1−

α

)+IBI_new*α

,

wherein IBI_i is a current estimation of the inter-beat interval, IBI_i-1 is a previous estimation of the inter-beat interval, IBI_new is a most recently-detected inter-beat interval, and α

is a weighting parameter.

15. A method as in claim 1, wherein said storing comprises minimizing storage requirements by only storing frames adjacent to a strong beat or to an offbeat.

16. A method as in claim 1, further comprising replacing a corrupted audio frame by interpolating preceding and succeeding audio frames.

17. A method as in claim 1, further comprising replacing a second part of the erroneous audio segment preceding the first part of the erroneous audio segment with a frame preceding the second part.

18. A method as in claim 1, further comprising replacing a second part of the erroneous audio segment following the first part of the erroneous audio segment with a frame following the second part.

19. A method as in claim 1, further comprising:

replacing a second part of the erroneous audio segment preceding the first part of the erroneous audio segment with a frame preceding the second part; and

replacing a third part of the erroneous audio segment following the first part of the erroneous audio segment with a frame following the third part.

20. A method as in claim 5, wherein said detecting a first beat and a subsequent plurality of beats further comprises:

detecting strong beats and off-beats, and

determining an interval between strong beats based on a statistical probability of inter-beat intervals.

21. A method as in claim 20, wherein said detecting a first beat and a subsequent plurality of beats further comprises:

determining the interval between strong beats based on a most probable inter-beat interval of approximately 600 ms.

22. A wireless terminal comprising:

a receiver section having a beat detector and an audio decoder, wherein the receiver section is configured to perform steps comprising

detecting a first beat and a subsequent plurality of beats in an audio bit stream,

defining a first inter-beat interval extending between said first beat and a (k+1)^th subsequent beat,

storing at least a portion of the audio bit stream occurring within said first inter-beat interval,

detecting an erroneous audio segment occurring in a second inter-beat interval extending between said (k+1)^th beat and a (2k+1)^th subsequent beat, and

replacing at least a first part of said erroneous audio segment with a corresponding part of said stored audio bit stream portion, wherein the corresponding part is selected based on a time relationship between the first part and one of the (k+1)^th and (2k+1)^th beats.

23. The wireless terminal of claim 22, wherein ‘

k’

is an integer greater than or equal to 2.

24. The wireless terminal of claim 22, wherein said stored audio bit stream portion includes at least one frame positioned on at least one of said beats.

25. The wireless terminal of claim 22, wherein said step of detecting a first beat comprises a step of computing the variance of the audio bit stream using decoded IMDCT coefficients.

26. The wireless terminal of claim 22, wherein said step of detecting a first beat comprises the step of utilizing a window-switching pattern.

27. The wireless terminal of claim 22, wherein said step of detecting a first beat comprises a step of computing the envelope of the audio bit stream using decoded IMDCT coefficients.

28. The wireless terminal of claim 22, wherein said step of detecting a first beat comprises steps of computing the variance of the audio bit stream using decoded IMDCT coefficients and utilizing a window-switching pattern.

29. The wireless terminal of claim 22, wherein said step of storing at least a portion of the audio bit stream includes a step of storing said portion in a circular first-in first-out (FIFO) buffer.

30. The wireless terminal of claim 22, wherein the audio bit stream includes a music signal.

31. The wireless terminal of claim 22, wherein the erroneous audio segment is the result of at least one of a frame loss from an IP network and a burst error from a wireless channel.

32. The wireless terminal of claim 22, wherein the first part has a time displacement τ

from one of the (k+1)^th and (2k+1)^th beats, and wherein the corresponding part is selected so as to have the same time displacement τ

from one of the first and (k+1)^th beats.

33. The wireless terminal of claim 22, wherein the receiver section is configured to perform steps comprising:

determining a confidence score, the confidence score being a percentage of correct beat detection within an observation window, and

discontinuing said replacing step when the confidence score is below a threshold value.

34. The wireless terminal of claim 22, wherein the receiver section is configured to perform steps comprising:

estimating an inter-beat interval according to the formula

IBI_i=IBI_i-1*(1−

α

)+IBI_new *α

,

wherein lBI_i is a current estimation of the inter-beat interval, IBI_i-1 is a previous estimation of the inter-beat interval, IBI_new is a most recently-detected inter-beat interval, and α

is a weighting parameter.

35. The wireless terminal of claim 22, wherein said storing comprises minimizing storage requirements by only storing frames adjacent to a strong beat or to an offbeat.

36. The wireless terminal of claim 22, wherein the receiver section is configured to perform steps comprising:

replacing a corrupted audio frame by interpolating preceding and succeeding audio frames.

37. The wireless terminal of claim 22, wherein the receiver section is configured to perform steps comprising:

replacing a second part of the erroneous audio segment preceding the first part of the erroneous audio segment with a frame preceding the second part.

38. The wireless terminal of claim 22, wherein the receiver section is configured to perform steps comprising:

replacing a second part of the erroneous audio segment following the first part of the erroneous audio segment with a frame following the second part.

39. The wireless terminal of claim 22, wherein the receiver section is configured to perform steps comprising:

replacing a second part of the erroneous audio segment preceding the first part of the erroneous audio segment with a frame preceding the second part, and

replacing a third part of the erroneous audio segment following the first part of the erroneous audio segment with a frame following the third part.

40. The wireless terminal of claim 26, wherein said detecting a first beat and a subsequent plurality of beats further comprises:

detecting strong beats and off-beats, and

determining an interval between strong beats based on a statistical probability of inter-beat intervals.

41. The wireless terminal of claim 40, wherein said detecting a first beat and a subsequent plurality of beats further comprises:

determining the interval between strong beats based on a most probable inter-beat interval of approximately 600 ms.

42. The wireless terminal of claim 22, wherein the receiver section is configured to perform the step of replacing one beat with another beat from a preceding bar.