Methods and Apparatus For Mixing Compressed Digital Bit Streams

• US 20080253440A1
• Filed: 06/29/2005
• Published: 10/16/2008
• Est. Priority Date: 07/02/2004
• Status: Active Grant

• Current Assignee: The Nielsen Company LLC (MOOD Media Corporation)
• Original Assignee: The Nielsen Company LLC (MOOD Media Corporation)
• Inventors: Peiffer, John C., Srinivasan, Venugopal
• Granted Patent: US 8,412,363 B2
• Time in Patent Office: Days
• US Class Current: 375/240
• CPC Class Codes: G10L 19/008 Multichannel audio signal coding or decoding using interchannel correlation to reduce redundancy, e.g. joint-stereo, intensity-coding or matrixing
• CPC Class Codes: G10L 19/032 Quantisation or dequantisation of spectral components
• CPC Class Codes: G10L 19/173 Transcoding, i.e. converting between two coded representations avoiding cascaded coding-decoding
• CPC Class Codes: G11B 20/00007 Time or data compression or expansion audio compression based on psychoacoustics G10L19/00; data processing for reproducing audio data at different playback speeds G10L21/04; video compression H04N19/00; data compression per se H03M7/30
• CPC Class Codes: G11B 20/10527 Audio or video recording; Data buffering arrangements G11B20/12 - G11B20/18 take precedence
• CPC Class Codes: G11B 2020/00028 Advanced audio coding [AAC]
• CPC Class Codes: G11B 2020/00036 AC-3, i.e. ATSC digital audio compression standard
• CPC Class Codes: G11B 2020/10546 specifically adapted for audio data
• CPC Class Codes: G11B 27/034 on discs G11B27/036, G11B27/038 take precedence
• CPC Class Codes: H04N 5/265 Mixing

Abstract

Methods, apparatus and articles of manufacture for mixing compressed digital bit streams are disclosed. An example method disclosed herein comprises acquiring a frame associated with a first compressed digital bit stream, unpacking the frame to obtain a plurality of original transform coefficient sets, and modifying the plurality of original transform coefficient sets to mix a second digital bit stream with the first compressed digital bit stream.

Claims

1. A method of mixing a first compressed digital bit stream with a second digital bit stream, the method comprising:

acquiring a frame associated with the first compressed digital bit stream;

unpacking the frame to obtain a plurality of original transform coefficient sets; and

modifying the plurality of original transform coefficient sets to mix the second digital bit stream with the first compressed digital bit stream.

2. A method as defined in claim 1 wherein modifying the plurality of original transform coefficient sets comprises:

determining a first mantissa code associated with a mixed transform coefficient of one of a plurality of mixed transform coefficient sets; and

substituting the first mantissa code associated with the mixed transform coefficient for a second mantissa code associated with a corresponding original transform coefficient of one of the plurality of original transform coefficient sets.

3. A method as defined in claim 2 wherein determining the first mantissa code associated with the mixed transform coefficient of the one of the plurality of mixed transform coefficient sets comprises:

determining a quantization step size associated with the corresponding original transform coefficient of one of the plurality of original transform coefficient sets;

generating the mixed transform coefficient based on combining an element associated with the first compressed digital bit stream and an element associated with the second digital bit stream;

quantizing the mixed transform coefficient based on the quantization step size to generate a quantized mantissa; and

determining the first mantissa code associated with the mixed transform coefficient based on the quantized mantissa.

4. A method as defined in claim 3 wherein the quantization step size is based on an exponent associated with the corresponding original transform coefficient.

5. A method as defined in claim 3 wherein combining the element associated with the first compressed digital bit stream and the element associated with the second digital bit stream comprises adding the element associated with the first compressed digital bit stream and the element associated with the second digital bit stream.

6. A method as defined in claim 5 further comprising attenuating at least one of the element of the first compressed digital bit stream or the element of the second digital bit stream prior to adding the element of the first compressed digital bit stream and the element of the second digital bit stream.

7. A method as defined in claim 1 wherein modifying the plurality of original transform coefficient sets comprises:

generating a plurality of time-domain audio blocks based on the plurality of original transform coefficient sets;

generating a plurality of reconstructed audio blocks based on the plurality of time-domain audio blocks; and

generating a plurality of mixed audio blocks based on the plurality of reconstructed audio blocks and the second digital bit stream.

8. A method as defined in claim 7 wherein generating the plurality of reconstructed audio blocks based on the plurality of time-domain audio blocks comprises generating a reconstructed time-domain audio block based on a first time-domain audio block and a second time-domain audio block.

9. A method as defined in claim 8 wherein generating the reconstructed time-domain audio block based on the first time-domain audio block and the second time-domain audio block comprises adding the first and second time-domain audio blocks.

10. A method as defined in claim 1 wherein modifying the plurality of transform coefficient sets comprises modifying the plurality of original transform coefficient sets based on a plurality of mixed transform coefficient sets.

11. A method as defined in claim 10 further comprising generating a plurality of mixed coefficient sets by determining mantissa codes associated with mixed transform coefficients of each of the plurality mixed transform coefficient sets based on compression information associated with the first compressed digital bit stream.

12. A method as defined in claim 1 wherein each of the plurality of original transform coefficient sets comprises one or more modified discrete cosine transform coefficients.

13. A method as defined in claim 1 wherein the first compressed digital bit stream is compressed in accordance with an audio compression standard.

14. A method as defined in claim 1 wherein acquiring the frame associated with the first compressed digital bit stream comprises acquiring audio blocks associated with at least one of a plurality of audio channels.

15. A method as defined in claim 1 wherein unpacking the frame to obtain the plurality of original transform coefficient sets comprises determining compression information associated with the first compressed digital bit stream.

16. A method as defined in claim 1 further comprising repacking the frame based on a plurality of mixed transform coefficient sets.

17. A method as defined in claim 1 wherein the first compressed digital bit stream corresponds to a main audio service and the second digital bit stream corresponds to an auxiliary audio service.

18. A method as defined in claim 1 wherein the second digital bit stream is compressed.

19. A method as defined in claim 18 wherein a pseudo-noise signal is added to the second digital bit stream prior to compression.

20. A method as defined in claim 19 wherein modifying the plurality of original transform coefficient sets comprises:

determining a first mantissa code associated with a pseudo-noise transform coefficient of one of a plurality of pseudo-noise transform coefficient sets; and

modifying a second mantissa code associated with a corresponding original transform coefficient of one of the plurality of original transform coefficient sets based on the first mantissa code.

21. A method as defined in claim 20 wherein the plurality of pseudo-noise transform coefficient sets are determined based on an average spectral characteristic of the pseudo-noise signal.

22. A data stream mixing apparatus comprising:

an acquisition unit to acquire a frame associated with a first compressed digital data stream;

an unpacking unit to unpack the frame to obtain a plurality of original transform coefficient sets; and

a modification unit to modify the plurality of original transform coefficient sets to mix a second digital data stream with the first compressed digital data stream.

23. An apparatus as defined in claim 22 wherein the modification unit is configured to:

determine a first mantissa code associated with a mixed transform coefficient of one of a plurality of mixed transform coefficient sets; and

substitute the first mantissa code associated with the mixed transform coefficient for a second mantissa code associated with a corresponding original transform coefficient of one of the plurality of transform coefficient sets.

24. An apparatus as defined in claim 23 wherein the modification unit is configured to:

determine a quantization step size associated with the corresponding original transform coefficient of one of the plurality of original transform coefficient sets;

generate the mixed transform coefficient based on a combination of an element associated with the first compressed digital data stream and an element associated with the second digital data stream;

quantize the mixed transform coefficient based on the quantization step size to generate a quantized mantissa; and

determine the first mantissa code associated with the mixed transform coefficient based on the quantized mantissa.

25. An apparatus as defined in claim 24 wherein the quantization step size is based on an exponent associated with the corresponding original transform coefficient.

26. An apparatus as defined in claim 24 wherein the combination of the element associated with the first compressed digital data stream and the element associated with the second digital data stream comprises the addition of the element associated with the first compressed digital data stream and the element associated with the second digital data stream.

27. An apparatus as defined in claim 26 wherein the combination of the element associated with the first compressed digital data stream and the element associated with the second digital data stream further comprises the attenuation of at least one of the element associated with the first compressed digital data stream or the element associated with the second digital data stream prior to the addition of the element associated with the first compressed digital data stream and the element associated with the second digital data stream.

28. An apparatus as defined in claim 22 wherein the modification unit is configured to:

generate a plurality of time-domain audio blocks based on the original transform coefficient sets;

generate a plurality of reconstructed audio blocks based on the plurality of time-domain audio blocks; and

generate a plurality of mixed audio blocks based on the plurality of reconstructed audio blocks and the second digital data stream.

29. An apparatus as defined in claim 28 wherein the modification unit is configured to generate a reconstructed time-domain audio block in the plurality of reconstructed audio blocks based on a first time-domain audio block and a second time-domain audio block in the plurality of time-domain audio blocks.

30. An apparatus as defined in claim 29 wherein the modification unit is configured to add the first and second time-domain audio blocks to generate the reconstructed time-domain audio block.

31. An apparatus as defined in claim 22 wherein the modification unit is configured to modify the plurality of original transform coefficient sets based on a plurality of mixed transform coefficient sets.

32. An apparatus as defined in claim 31 wherein the modification unit is further configured to generate the plurality of mixed transform coefficient sets based on the second digital data stream and compression information associated with the first compressed digital data stream.

33. An apparatus as defined in claim 22 wherein each of the plurality of original transform coefficient sets comprises one or more modified discrete cosine transform coefficients.

34. An apparatus as defined in claim 22 wherein the first compressed digital data stream is compressed in accordance with an audio compression standard.

35. An apparatus as defined in claim 22 wherein the acquisition unit is configured to acquire audio blocks associated with a plurality of audio channels.

36. An apparatus as defined in claim 22 wherein the unpacking unit is configured to obtain compression information associated with the first compressed digital data stream.

37. An apparatus as defined in claim 22 wherein the first compressed digital data stream is associated with a main audio service and the second digital data stream is associated with an auxiliary audio service.

38. An apparatus as defined in claim 22 further comprising a repacking unit to repack the frame based on a plurality of mixed transform coefficient sets.

39. An article of manufacture storing machine readable instructions which, when executed, cause a machine to:

acquire a frame associated with a first compressed digital bit stream;

unpack the frame to obtain a plurality of original transform coefficient sets; and

modify the plurality of original transform coefficient sets to mix a second digital bit stream with the first compressed digital bit stream.

40. An article of manufacture as defined in claim 39 wherein the instructions, when executed, cause the machine to modify the plurality of original transform coefficient sets by:

determining a first mantissa code associated with a mixed transform coefficient of one of a plurality of mixed transform coefficient sets; and

substituting the first mantissa code associated with the mixed transform coefficient for a second mantissa code associated with a corresponding original transform coefficient of one of the plurality of original transform coefficient sets.

41. An article of manufacture as defined in claim 40 wherein the instructions, when executed, cause the machine to determine the first mantissa code associated with the mixed transform coefficient of the one of the plurality of mixed transform coefficient sets by:

determining a quantization step size associated with the corresponding original transform coefficient of one of the plurality of original transformed coefficient sets;

generating the mixed transform coefficient based on combining an element associated with the first compressed digital bit stream and an element associated with the second digital bit stream;

quantizing the mixed transform coefficient based on the quantization step size to generate a quantized mantissa; and

determining the first mantissa code associated with the mixed transform coefficient based on the quantized mantissa.

42. An article of manufacture as defined in claim 39 wherein the instructions, when executed, cause the machine to modify the plurality of original transform coefficient sets by:

generating a plurality of time-domain audio blocks based on the plurality of original transform coefficient sets;

generating a plurality of reconstructed audio blocks based on the plurality of time-domain audio blocks; and

generating a plurality of mixed audio blocks based on the plurality of reconstructed audio blocks and the second digital bit stream.

43. An article of manufacture as defined in claim 39 wherein the instructions, when executed, further cause the machine to generate a plurality of mixed coefficient sets by determining mantissa codes associated with mixed transform coefficients of each of the plurality of mixed coefficient sets based on compression information associated with the first compressed digital bit stream.

44. An article of manufacture as defined in claim 39 wherein the instructions, when executed, further cause the machine to acquire the frame associated with the first compressed digital bit stream by acquiring audio blocks associated with at least one of a plurality of audio channels.

45. An article of manufacture as defined in claim 39 wherein the instructions cause the machine to unpack the frame to obtain the plurality of original transform coefficient sets by identifying compression information associated with the first compressed digital bit stream.

46. An article of manufacture as defined in claim 39 wherein the instructions, when executed, further cause the machine to repack the frame based on a plurality of mixed transform coefficient sets.

47. An article of manufacture as defined in claim 39 wherein the first compressed digital bit stream is associated with a main audio service and the second digital bit stream is associated with an auxiliary audio service.

48. A system to mix digital data streams comprising

a first source to provide a first compressed digital data stream;

a second source to provide a second digital data stream; and

a mixing device to mix the second digital data stream with the first compressed digital data stream without uncompressing the first compressed digital data stream.

49. A system as defined in claim 48 wherein the first compressed digital data stream comprises a plurality of transform coefficients.

50. A system as defined in claim 49 wherein the mixing device is configured to modify the plurality of transform coefficients based on the second digital data stream.

51. A system as defined in claim 50 wherein the plurality of transform coefficients comprises respective pluralities of original mantissas and original exponents, and the mixing device is configured to modify only the plurality of original mantissas to modify the plurality of transform coefficients.

52. A system as defined in claim 51 wherein the plurality of transform coefficients is a plurality of original transform coefficients, and the mixing device is configured to modify the plurality of original transform coefficients by determining a plurality of mixed transform coefficients based on the second digital data stream and compression information associated with the first compressed digital data stream

53. A system as defined in claim 52 wherein the compression information comprises at least one quantization step size.

54. A system as defined in claim 52 wherein determining the plurality of mixed transform coefficients comprises quantizing a plurality of mixed mantissas associated with the mixed transform coefficients.

55. A system as defined in claim 54 wherein the mixing device is configured to modify the plurality of original mantissas based on the plurality of quantized mixed mantissas and the compression information.

56. A system as defined in claim 48 wherein the first compressed digital data stream is compressed according to an audio compression standard.

57. A system as defined in claim 48 wherein the first compressed digital data stream is associated with a main audio service and the second digital data stream is associated with an auxiliary data service.

58. A system as defined in claim 48 wherein the second digital data stream is uncompressed.

59. A method of combining a first compressed digital data stream with a second digital data stream, the method comprising:

acquiring a frame associated with the first compressed digital data stream;

unpacking the frame to obtain a plurality of original transform coefficient sets; and

modifying the plurality of original transform coefficient sets to combine the second digital data stream with the first compressed digital data stream.

60. A method as defined in claim 59 wherein combining comprises mixing and wherein modifying the plurality of original transform coefficient sets to combine the second digital data stream with the first compressed digital data stream comprises modifying the plurality of original transform coefficient sets to mix the second digital data stream with the first compressed digital data stream.

61. A method as defined in claim 59 wherein modifying the plurality of original transform coefficient sets comprises:

determining a first mantissa code associated with a mixed transform coefficient of one of a plurality of mixed transform coefficient sets; and

substituting the first mantissa code associated with the mixed transform coefficient for a second mantissa code associated with a corresponding original transform coefficient of one of the plurality of original transform coefficient sets.

62. A method as defined in claim 59 wherein each of the plurality of original transform coefficient sets comprises one or more modified discrete cosine transform coefficients.