Method and system for reduction of quantization-induced block-discontinuities and general purpose audio codec

• US 6,370,502 B1
• Filed: 05/27/1999
• Issued: 04/09/2002
• Est. Priority Date: 05/27/1999
• Status: Expired due to Term

• Current Assignee: Meta Platforms, Inc. (f/k/a Facebook, Inc.)
• Original Assignee: America Online Inc. (Warner Bros. Discovery, Inc.)
• Inventors: Perlmutter, Keren, Mantegna, John, Wu, Shuwu
• Primary Examiner(s): Dorvil, Richemond
• Assistant Examiner(s): MCFADDEN, SUSAN IRIS
• Application Number:
  US09/321,488
• Time in Patent Office: 1,048 Days
• Field of Search: 704/230, 704/222, 704/229, 704/205, 704/203, 704/224, 704/225, 704/508, 704/501
• US Class Current: 704/230
• CPC Class Codes: G10L 19/00 Speech or audio signals analysis-synthesis techniques for redundancy reduction, e.g. in vocoders; Coding or decoding of speech or audio signals, using source filter models or psychoacoustic analysis in musical instruments G10H
• CPC Class Codes: G10L 19/0212 using orthogonal transformation
• CPC Class Codes: G10L 19/022 Blocking, i.e. grouping of samples in time; Choice of analysis windows; Overlap factoring
• CPC Class Codes: G10L 19/028 Noise substitution, i.e. substituting non-tonal spectral components by noisy source comfort noise for discontinuous speech transmission G10L19/012
• CPC Class Codes: G10L 19/038 Vector quantisation, e.g. TwinVQ audio
• CPC Class Codes: G10L 2019/0012 Smoothing of parameters of the decoder interpolation

Abstract

A method and system for reduction of quantization-induced block-discontinuities arising from lossy compression and decompression of continuous signals, especially audio signals. One embodiment encompasses a general purpose, ultra-low latency, efficient audio codec algorithm. More particularly, the invention includes a method and apparatus for compression and decompression of audio signals using a novel boundary analysis and synthesis framework to substantially reduce quantization-induced frame or block-discontinuity; a novel adaptive cosine packet transform (ACPT) as the transform of choice to effectively capture the input audio characteristics; a signal-residue classifier to separate the strong signal clusters from the noise and weak signal components (collectively called residue); an adaptive sparse vector quantization (ASVQ) algorithm for signal components; a stochastic noise model for the residue; and an associated rate control algorithm. The invention further includes corresponding computer program implementations of these and other algorithms.

Claims

1. A zero-latency method for reducing quantization-induced block-discontinuities of continuous data formatted into a plurality of time-domain blocks having boundaries, including:

performing a first quantization of each block and generating first quantization indices indicative of such first quantization;

determining a quantization error for each block;

selecting any quantization error arising near the boundaries of each block from such first quantization;

performing a second quantization of any selected quantization error and generating second quantization indices indicative of such second quantization; and

generating an output bit-stream based on the first and second quantization indices.

2. The method of claim 1, wherein the continuous data is audio data.

3. The method of claim 2, further including:

transforming each time-domain block of audio data to a transform domain block comprising a plurality of coefficients;

partitioning the coefficients of each time-domain block into signal coefficients

quantizing the signal coefficients for each block and generating signal quantization indices indicative of such quantization; and

modeling the residue coefficients for each block as stochastic noise and generating residue quantization indices indicative of such quantization.

4. The method of claim 1, wherein generating the output bit-stream includes encoding the first and second quantization indices and formatting such encoded indices as the output bit-stream.

5. The method of claim 1, wherein the continuous data includes continuous time-domain data, wherein the method further comprises formatting the continuous time-domain data into a plurality of time-domain blocks having boundaries.

6. A zero-latency method for reducing quantization-induced block-discontinuities of continuous data formatted into a plurality of contiguous original time-domain blocks, including:

performing a reversible transform on each original time-domain block into a corresponding transformed block that yields energy concentration in the transformed domain;

performing a first quantization of each transformed block and generating first quantization indices indicative of such first quantization;

performing the inverse transform on quantized transform components of the first quantization indices for each transformed block, yielding a corresponding quantized time-domain block;

computing a quantization error by taking the difference between the original time-domain block and its corresponding quantized time-domain block;

selecting the quantization error arising near the boundaries of each original time-domain block from such first quantization;

performing a second quantization on the selected quantization error and generating second quantization indices indicative of such second quantization; and

generating an output bit-stream based on the first and second quantization indices.

7. The method of claim 6, wherein the continuous data is audio data.

8. The method of claim 6, further including applying a windowing function to each original time-domain block to enhance residue energy concentration near the boundaries of each such original time-domain block.

9. The method of claim 8, wherein the windowing function is substantially characterized by the identity function but with bell-shaped decays near the boundaries of a block.

10. The method of claim 6 generating the output bit-stream includes encoding the first and second quantization indices and formatting such encoded indices as the output bit-stream.

11. The method of claim 6, wherein the continuous data includes continuous time-domain data, wherein the method further comprises formatting the continuous time-domain data into a plurality of contiguous original time-domain blocks.

12. A computer program, residing on a computer-readable medium, for zero-latency reduction of quantization-induced block-discontinuities of continuous data formatted into a plurality of time-domain blocks having boundaries, the computer program comprising instructions for causing a computer to:

perform a first quantization of each block and generate first quantization indices indicative of such first quantization;

determine a quantization error for each block;

select any quantization error arising near the boundaries of each block from such first quantization;

perform a second quantization of any selected quantization error and generate second quantization indices indicative of such second quantization; and

generate an output bit-stream based on the first and second quantization indices.

13. The computer program of claim 12, wherein the continuous data is audio data.

14. The computer program of claim 13, further including instructions for causing the computer to:

transform each time-domain block of audio data to a transform domain block comprising a plurality of coefficients;

partition the coefficients of each time-domain block into signal coefficients and residue coefficients;

quantize the signal coefficients for each block and generate signal quantization indices indicative of such quantization; and

model the residue coefficients for each block as stochastic noise and generate residue quantization indices indicative of such quantization.

15. The computer program of claim 12, wherein the instructions for causing the computer to generate the output bit-stream include instructions for causing the computer to encode the first and second quantization indices and format such encoded indices as the output bit-stream.

16. The computer program of claim 12, wherein the continuous data includes continuous time-domain data, wherein the computer program further comprises instructions for causing the computer to format the continuous time-domain data into a plurality of time-domain blocks having boundaries.

17. A computer program, residing on a computer-readable medium, for zero-latency reduction of quantization-induced block-discontinuities of continuous data formatted into a plurality of contiguous original time-domain blocks, the computer program comprising instructions for causing a computer to:

perform a reversible transform on each original time-domain block into a corresponding transformed block that yields energy concentration in the transformed domain;

perform a first quantization of each transformed block and generate first quantization indices indicative of such first quantization;

perform the inverse transform on quantized transform components of the first quantization indices for each transformed block, yielding a corresponding quantized time-domain block;

compute a quantization error by taking the difference between the original time-domain block and its corresponding quantized time-domain block;

select the quantization error arising near the boundaries of each original time-domain block from such first quantization;

perform a second quantization on the selected quantization error and generate second quantization indices indicative of such second quantization; and

generate an output bit-stream based on the first and second quantization indices.

18. The computer program of claim 17, wherein the continuous data is audio data.

19. The computer program of claim 17, further including instructions for causing the computer to apply a windowing function to each original time-domain block to enhance residue energy concentration near the boundaries of each such original time-domain block.

20. The computer program of claim 19, wherein the windowing function is substantially characterized by the identity function but with bell-shaped decays near the boundaries of a block.

21. The computer program of claim 17, wherein the instructions for causing the computer to generate the output bit-stream include instructions for causing the computer to encode the first and second quantization indices and format such encoded indices as the output bit-stream.

22. The computer program of claim 17, wherein the continuous data includes continuous time-domain data, wherein the computer program further comprises instructions for causing the computer to format the continuous time-domain data into a plurality of contiguous original time-domain blocks.

23. A system for zero-latency reduction of quantization-induced block-discontinuities of continuous data formatted into a pluarlity of time-domain blocks having boundaries, including:

means for performing a first quantization of each block and generating first quantization indices indicative of such first quantization;

means for determining a quantization error for each block;

means for selecting any quantization error arising near the boundaries of each block from such first quantization;

means for performing a second quantization of any selected quantization error and generating second quantization indices indicative of such second quantization; and

means for generating an output bit-stream based on the first and second quantization indices.

24. The system of claim 23, wherein the continuous data is audio data.

25. The system of claim 24, further including:

means for transforming each time-domain block of audio data to a transform domain block comprising a plurality of coefficients;

means for partitioning the coefficients of each time-domain block into signal coefficients and residue coefficients;

means for quantizing the signal coefficients for each block and generating signal quantization indices indicative of such quantization; and

means for modeling the residue coefficients for each block as stochastic noise and generating residue quantization indices indicative of such quantization.

26. The system of claim 23, wherein the means for generating the output bit-stream includes means for encoding the first and second quantization indices and formatting such encoded indices as the output bit-stream.

27. The system of claim 23, wherein the continuous data includes continuous time-domain data, wherein the system further comprises means for formatting the continuous time-domain data into a plurality of time-domain blocks having boundaries.

28. A system for zero-latency reduction of quantization-induced block-discontinuities of continuous data formatted into a plurality of contiguous original time-domain blocks, including:

means for performing a reversible transform on each original time-domain block into a corresponding transformed block that yields energy concentration in the transformed domain;

means for performing a first quantization of each transformed block and generating first quantization indices indicative of such first quantization;

means for performing the inverse transform on quantized transform components of the first quantization indices for each transformed block, yielding a corresponding quantized time-domain block;

means for computing a quantization error by taking the difference between the original time-domain block and its corresponding quantized time-domain block;

means for selecting the quantization error arising near the boundaries of each original time-domain block from such first quantization;

means for performing a second quantization on the selected quantization error and generating second quantization indices indicative of such second quantization; and

means for generating an ouput bit-stream based on the first and second quantization indices.

29. The system of claim 28, wherein the continuous data is audio data.

30. The system of claim 28, further including means for applying a windowing function to each original time-domain block to enhance residue energy concentration near the boundaries of each such original time-domain block.

31. The system of claim 30, wherein the windowing function is substantially characterized by the identity function but with bell-shaped decays near the boundaries of a block.

32. The system of claim 28, wherein the means for generating the output bit-stream includes means for encoding the first and second quantization indices and formatting such encoded indices as the output bit-stream.

33. The system of claim 28, wherein the continuous data includes continuous time-domain data, wherein the system further comprises means for formatting the continuous time-domain data into a plurality of contiguous original time-domain blocks.