Method and apparatus for adaptive audio compression and decompression

• US 5,832,443 A
• Filed: 02/25/1997
• Issued: 11/03/1998
• Est. Priority Date: 02/25/1997
• Status: Expired due to Term

• Current Assignee: Joint Venture, XVD Technology Holdings Ltd.
• Original Assignee: Alaris, Inc., GT Technologies
• Inventors: Trofimov, Andrei, Kudryashov, Boris, Kolesnik, Victor D., Bocharova, Irina, Troyanovsky, Boris, Ovsyannikov, Eugene
• Primary Examiner(s): Hudspeth, David R.
• Assistant Examiner(s): Wieland, Susan
• Application Number:
  US08/806,075
• Time in Patent Office: 616 Days
• Field of Search: 704/500-504, 704/200, 704/201, 704/205, 704/206, 704/212, 704/222, 704/229, 704/268, 704/269
• US Class Current: 704/500
• CPC Class Codes: G10L 19/0212 using orthogonal transformation

Abstract

A method and apparatus for compression and decompression of an audio signal. In encoding an input audio signal, at least a portion of the audio signal is transformed into a set of coefficients. A set of binary vectors associated with the set of coefficients are generated for digitizing the transformed audio signal using a fixed rate adaptive quantization. Information based on the set of binary vectors is combinatorially encoded and output as a bit stream of encoded audio data. The encoded audio data may be stored, transmitted, and/or decoded.

Claims

1. A machine implemented method to compress audio data, said audio data representing an audio signal, said method comprising:

receiving said audio data;

decomposing said audio signal into a set of frames;

transforming values representing a first frame of said set of frames into a set of transform coefficients;

generating a set of binary vectors representing magnitudes of said set of transform coefficients;

combinatorially encoding said set of binary vectors; and

storing said combinatorially encoded set of binary vectors.

2. The method of claim 1, further comprising filtering said audio signal.

3. The method of claim 1, wherein said audio signal comprises speech.

4. The method of claim 1, further comprising:

transforming said values using a Fast Fourier Transform (FFT).

5. The method of claim 1, further comprising:

separating the signs from said set of transform coefficients prior to generating said set of binary vectors; and

storing indications identifying said signs of said set of transform coefficients.

6. The method of claim 1, further comprising:

selecting a subset of transform coefficients from said set of transform coefficients;

generating said set of binary vectors based on said subset of transform coefficients; and

generating a second binary vector representing locations in said first frame of said subset of transform coefficient.

7. The method of claim 6 further comprising:

combinatorially encoding said second binary vector; and

storing said combinatorially encoded second binary vector.

8. The method of claim 1, wherein generating said set of binary vectors further comprises grouping the magnitudes to be represented by said set of binary vectors into a set of groups according to a composition, said composition determining said set of groups based on a predetermined quantity and relative value of said magnitudes in each group in said set of groups.

9. The method of claim 8, wherein generating said set of binary vectors further includes:

creating a set of binary rank vectors that each identify a different one of said set of groups, said set of binary rank vectors being in said set of binary vectors.

10. The method of claim 8, further comprising selecting said composition from a set of predetermined compositions based on determining relative error associated with each of said set of predetermined compositions.

11. The method of claim 8, further comprising:

averaging the magnitudes in each group of said set of groups to generate a set of averaged magnitudes;

locating entries in a quantization scale that approximate said set of averaged magnitudes; and

generating a binary indicator vector identifying located entries, said binary indicator vector being in said set of binary vectors.

12. The method of claim 11, further comprising selecting said quantization scale from a set of predetermined scales based on determining relative error associated with each of said set of predetermined scales.

13. A machine implemented method to compress data associated with coefficients representing a frame of audio data, said audio data representing an audio signal, said coefficients having an order, said method comprising:

separating the signs from said coefficients to create a first vector identifying said signs of said coefficients and a second vector identifying the magnitudes of said coefficients;

generating a set of binary vectors representing said second vector, each binary vector in said set of binary vectors having a predetermined length and containing a predetermined number of a particular type of bit;

encoding said set of binary vectors to generate encoded data; and

storing said encoded data.

14. The method of claim 13, wherein generating said set of binary vectors further comprises:

grouping said magnitudes into a set of groups according to a composition, said composition dictating the number and relative value of said magnitudes in each group of said set of groups;

creating a set of binary rank vectors indicating the locations relative to said order of said coefficients according to said set of groups, said set of binary rank vectors being in said set of binary vectors;

averaging said magnitudes in each of said set of groups of magnitudes to create a plurality of averages; and

quantizing said plurality of averages to create an indicator vector, said indicator vector being in said set of binary vectors.

15. The method of claim 13, wherein encoding said set of binary vectors further comprises combinatorially encoding said set of binary vectors to create said encoded data.

16. The method of claim 13, further comprising:

transmitting said first vector and said combinatorially encoded data.

17. The method of claim 13, further comprising:

transforming values in said frame using a Fast Fourier Transform to generate said coefficients.

18. An audio encoder comprising:

a transform unit to transform data representing a frame of an audio signal into transform coefficients;

a quantizer, coupled to said transform unit, to group magnitudes of a set of said transform coefficients into a set of groups according to a composition, said composition determining the number and relative value of said magnitudes in each group of said set of groups, said quantizer to provide a set of binary vectors that represent a quantization of said magnitudes according to said composition; and

a combinatorial encoder, coupled to said quantizer, to combinatorially encode said set of binary vectors.

19. The apparatus of claim 18, wherein said transform unit performs Fast Fourier Transform (FFT).

20. The apparatus of claim 18, wherein said frame partially overlaps another frame of said audio signal.

21. The apparatus of claim 18 further comprising:

a selector, coupled to said transform unit and said quantizer, to separate signs from said set of said transform coefficients to generate said magnitudes.

23. The apparatus of claim 18, wherein said composition is an optimum composition that is selected from a plurality of compositions based on determining relative error associated with each of said plurality of compositions.

24. The apparatus of claim 18, wherein said quantizer averages said magnitudes in each of said set of groups to generate a set of averaged magnitudes and determines quantization values in a quantization scale for said set of averaged magnitudes.

25. The apparatus of claim 24, wherein said quantization scale is an optimum quantization scale that is selected from a plurality of quantization scales based on determining relative error associated with each of said plurality of quantization scales.

26. The apparatus of claim 18, wherein said quantizer includes:

a rank vector former coupled to receive said magnitudes and said composition, said rank vector former also coupled to said encoder to deliver a subset of said set of binary vectors, said subset of said set of binary vectors to indicate which of said set of said transform coefficients are in each group of said set of groups.

27. The apparatus of claim 26, wherein said quantizer further includes:

an average vector former coupled to said rank vector encoder to receive said subset and coupled to receive said magnitudes;

a quantized average vector former coupled to said average vector former to receive an average vector representing the averages of the magnitudes in each group of said set of groups; and

an indicator vector former coupled to said quantized average vector former and said encoder to provide one of said set of binary vectors.

22. The apparatus of claim 22, wherein said selector generates a binary location vector that identifies the relative locations in said frame of said set of said transform coefficients and provides said binary location vector to said encoder.

28. A machine implemented method for decompression of compressed data representing a frame of an audio signal, said compressed data comprising a set of binary vectors, said method comprising:

decoding said set of binary vectors using combinatorial decoding;

determining a set of values representing said audio signal from said combinatorially decoded set of binary vectors by;

determining a set of magnitudes using a subset of said set of binary vectors;

determining a sign for each magnitude in said set of magnitudes using a sign vector extracted from said compressed data;

combining said set of magnitudes with the signs to generate a set of coefficients;

identifying locations of said set of coefficients in said frame using a location vector in said set of binary vectors;

inverse transforming said set of coefficients to generate said set of values; and

synthesizing said frame of said audio signal from said set of values.

29. The method of claim 28, wherein determining said set of values includes performing an inverse Fast Fourier Transform (IFFT) operation to determine said set of values.

30. The method of claim 28, further comprising:

determining a set of groups based on a composition and a set of rank vectors in said subset, said composition dictating said groupings based on a predetermined quantity and relative value of said set of magnitudes in each group in said set of groups, said set of groups dictating an overall order of said set of magnitudes;

determining a set of entries in a quantization scale based on an indicator vector in said subset, each group in said set of groups corresponding to one entry in said set of entries; and

identifying said set of magnitudes and the order of said set of magnitudes based on said set of groups and said set of entries.

31. A machine implemented method for decompression of compressed data representing a frame of an audio signal, said method comprising:

extracting from said compressed data a set of binary vectors, said set of binary vectors representing grouping of magnitudes into a set of groups according to a composition, said composition dictating said set of groups based on a predetermined quantity and relative value of said magnitudes in each group in said set of groups, said set of binary vectors also identifying an order to said magnitudes;

extracting from said compressed data an indicator vector identifying a set of entries in a quantization scale, each group in said set of groups corresponding to one entry in said set of entries;

identifying said magnitudes and the order of said magnitudes based on said set of groups and said set of entries; and

synthesizing said frame using said set of magnitudes.

32. The method of claim 31, wherein extracting from said compressed data said set of binary vectors includes combinatorially decoding said compressed data.

33. The method of claim 31, wherein synthesizing said frame using said magnitudes includes:

extracting from said compressed data a sign vector identifying a corresponding sign for each of said magnitudes; and

combining each of said magnitudes with the corresponding sign to generate a set of coefficients.

34. The method of claim 33, wherein synthesizing said frame using said set of magnitudes includes:

inverse transforming said set of coefficients to generate a set of values; and

synthesizing said frame from said set of values.

35. The method of claim 34, wherein synthesizing said frame using said set of magnitudes includes:

extracting from said compressed data a location vector identifying the locations of said set of coefficients in said frame.

36. An audio encoder comprising:

a transform unit to transform data representing a frame of an audio signal into transform coefficients;

a quantizer, coupled to said transform unit, to group magnitudes of a set of said transform coefficients into a set of groups according to a composition, said composition determining the number and relative value of said magnitudes in each group of said set of groups, said quantizer to provide a set of binary vectors that represent a quantization of said magnitudes according to said composition;

a selector, coupled to said transform unit and said quantizer, to separate signs from said set of said transform coefficients to generate said magnitudes, and wherein said selector generates a binary location vector that identifies the relative locations in said frame of said set of said transform coefficients and outputs said binary location vector; and

an encoder, coupled to said quantizer and said selector, to encode said set of binary vectors and said binary location vector.

37. The apparatus of claim 36, wherein said encoder is a combinatorial encoder to combinatorially encode said set of binary vectors.

38. An audio encoder comprising:

a transform unit to transform data representing a frame of an audio signal into transform coefficients;

a quantizer, coupled to said transform unit, to group magnitudes of a set of said transform coefficients into a set of groups according to a composition, said composition determining the number and relative value of said magnitudes in each group of said set of groups, said quantizer to provide a set of binary vectors that represent a quantization of said magnitudes according to said composition wherein said quantizer comprises;

a rank vector former coupled to receive said magnitudes and said composition, said rank vector former also to provide a subset of said set of binary vectors, said subset of said set of binary vectors indicating which of said set of said transform coefficients are in each group of said set of groups;

a selector, coupled to said transform unit and said quantizer, to separate signs from said set of said transform coefficients to generate said magnitudes, and wherein said selector generates a binary location vector that identifies the relative locations in said frame of said set of said transform coefficients and outputs said binary location vector; and

an encoder, coupled to said quantizer and said selector, to encode said set of binary vectors and said binary location vector.

39. The apparatus of claim 38, wherein said quantizer further includes:

an average vector former coupled to said rank vector encoder to receive said subset and coupled to receive said magnitudes;

a quantized average vector former coupled to said average vector former to receive an average vector representing the averages of the magnitudes in each group of said set of groups; and

an indicator vector former coupled to said quantized average vector former and said encoder to provide one of said set of binary vectors.

40. The apparatus of claim 38, wherein said encoder is a combinatorial encoder to combinatorially encode said set of binary vectors.