Method and system for operating audio encoders utilizing data from overlapping audio segments

• US 7,418,394 B2
• Filed: 04/28/2005
• Issued: 08/26/2008
• Est. Priority Date: 04/28/2005
• Status: Active Grant

• Current Assignee: Dolby Laboratories Licensing Corporation (Dolby Laboratories Incorporated)
• Original Assignee: Dolby Laboratories Licensing Corporation (Dolby Laboratories Incorporated)
• Inventors: Cowdery, James Stuart Jeremy
• Primary Examiner(s): Hudspeth; David R.
• Assistant Examiner(s): KOVACEK, DAVID M
• Application Number:
  US11/119,341
• Publication Number:
  US 20060247928A1
• Time in Patent Office: 1,216 Days
• Field of Search: 704200-201, 704211-219, 704222-224, 704229-230, 704500-501, 704E19001-E19005, 381104-109
• US Class Current: 704/500
• CPC Class Codes: G10L 19/022 Blocking, i.e. grouping of samples in time; Choice of analysis windows; Overlap factoring

Abstract

The time needed to encode an input audio stream is reduced by dividing the stream into two or more overlapping segments of audio information blocks, applying an encoding process to each segment to generate encoded segments in parallel, and appending the encoded segments to form an encoded output signal. The encoding process is responsive to one or more control parameters. Some of the control parameters, which apply to a given block, are calculated from audio information in one or more previous blocks. The length of the overlap between adjacent segments is chosen such that the differences between control parameter values and corresponding reference values at the end of the overlap interval are small enough to avoid producing audible artifacts in a signal that is obtained by decoding the encoded output signal.

Claims

1. A method for encoding a stream of audio information comprising audio samples arranged in a sequence of blocks, each block having a respective start and end, wherein a first block precedes a second block, a third block follows the second block, a fourth block immediately follows the third block, and a fifth block follows the fourth block, and wherein the method comprises:

(a) identifying first and second segments of the stream of audio information that overlap one another by an overlap interval, wherein

(1) the first segment comprises a plurality of blocks that starts with the first block and ends with the third block,

(2) the second segment comprises a plurality of blocks that starts with the second block, includes the fourth block, and ends with the fifth block, and

(3) the overlap interval extends from the start of the second block to the start of the fourth block;

(b) applying a first encoding process to the first segment of the stream of audio information to generate blocks of first encoded audio information and a first control parameter corresponding to blocks of audio samples up to and including the third block, wherein

(1) the first encoded audio information in a block is generated in response to a corresponding block of audio samples in the first segment of the stream of audio information up to and including the third block;

(2) the first control parameter in the block is generated in response to the corresponding block of audio samples and preceding blocks of audio samples in the first segment of the stream of audio information from the first block up to and including the third block, and

(c) applying a second encoding process to the second segment of the stream of audio information to generate blocks of second encoded audio information and a second control parameter corresponding to blocks of audio samples from the fourth block up to and including the fifth block, and to generate a second control parameter corresponding to audio samples in the third block, wherein

(1) the second encoded audio information in a block is generated in response to a corresponding block of audio samples in the second segment of the stream of audio information from the fourth block up to and including the fifth block,

(2) the second control parameter in the block is generated in response to the corresponding block of audio samples and preceding blocks of audio samples in the second segment of the stream of audio information from the second block up to and including the fifth block, and

(3) the overlap interval is such that a difference between values of the first and second control parameters for the third block is less than a threshold amount; and

(d) assembling the blocks of first and second encoded audio information into an output signal, wherein

(1) the first and second control parameters are assembled into the output signal, or

(2) the first encoding process generates the first encoded audio information in response to the first control parameter and the second encoding process generates the second encoded audio information in response to the second control parameter.

2. The method according to claim 1, wherein the stream of audio information is arranged in frames, each frame having a plurality of blocks, the first, second and fourth blocks are beginning blocks in respective frames, and the third and fifth blocks are ending blocks in respective frames.

3. The method according to claim 1, wherein the first and second encoding processes generate encoded audio information by applying filterbanks to the blocks of audio samples that cause time-domain aliasing artifacts to be generated by complementary decoding processes applied to the encoded audio information, and the blocks of audio samples in the sequence of blocks overlap one another by an amount that allows the complementary decoding processes to mitigate effects of the time-domain aliasing artifacts.

4. The method of claim 1, wherein the first and second control parameters are assembled into the output signal and the overlap interval is greater than thirty-five seconds.

5. The method of claim 1, wherein the first and second encoding processes are responsive to the first and second control parameters, respectively, and the overlap interval is greater than 4,500 milliseconds.

6. The method of claim 1, wherein the threshold amount is such that differences in audio signals decoded from encoded audio information for the third block according to the first and second control parameters are imperceptible.

7. The method of claim 1, wherein the first and second control parameters represent values of a factor used in a decoding process that is complementary to the first and second encoding processes, and wherein the threshold amount represents a change in the factor equal to 1 dB.

8. The method of claim 1, wherein the first and second control parameters are represented by values that are quantized according to a quantization step size and the threshold amount is an integer number of quantization step sizes greater than or equal to zero.

9. An apparatus for encoding a stream of audio information comprising audio samples arranged in a sequence of blocks, each block having a respective start and end, wherein a first block precedes a second block, a third block follows the second block, a fourth block immediately follows the third block, and a fifth block follows the fourth block, wherein the apparatus comprises:

(a) means for identifying first and second segments of the stream of audio information that overlap one another by an overlap interval, wherein

(1) the first segment comprises a plurality of blocks that starts with the first block and ends with the third block,

(2) the second segment comprises a plurality of blocks that starts with the second block, includes the fourth block, and ends with the fifth block, and

(3) the overlap interval extends from the start of the second block to the start of the fourth block;

(b) means for applying a first encoding process to the first segment of the stream of audio information to generate blocks of first encoded audio information and a first control parameter corresponding to blocks of audio samples up to and including the third block, wherein

(1) the first encoded audio information in a block is generated in response to a corresponding block of audio samples in the first segment of the stream of audio information up to and including the third block;

(2) the first control parameter in the block is generated in response to the corresponding block of audio samples and preceding blocks of audio samples in the first segment of the stream of audio information from the first block up to and including the third block, and

(c) means for applying a second encoding process to the second segment of the stream of audio information to generate blocks of second encoded audio information and a second control parameter corresponding to blocks of audio samples from the fourth block up to and including the fifth block, and to generate a second control parameter corresponding to audio samples in the third block, wherein

(1) the second encoded audio information in a block is generated in response to a corresponding block of audio samples in the second segment of the stream of audio information from the fourth block up to and including the fifth block,

(2) the second control parameter in the block is generated in response to the corresponding block of audio samples and preceding blocks of audio samples in the second segment of the stream of audio information from the second block up to and including the fifth block, and

(3) the overlap interval is such that a difference between values of the first and second control parameters for the third block is less than a threshold amount; and

(d) means for assembling the blocks of first and second encoded audio information into an output signal, wherein

(1) the first and second control parameters are assembled into the output signal, or

(2) the first encoding process generates the first encoded audio information in response to the first control parameter and the second encoding process generates the second encoded audio information in response to the second control parameter.

10. The apparatus according to claim 9, wherein the stream of audio information is arranged in frames, each frame having a plurality of blocks, the first, second and fourth blocks are beginning blocks in respective frames, and the third and fifth blocks are ending blocks in respective frames.

11. The apparatus according to claim 9, wherein the first and second encoding processes generate encoded audio information by applying filterbanks to the blocks of audio samples that cause time-domain aliasing artifacts to be generated by complementary decoding processes applied to the encoded audio information, and the blocks of audio samples in the sequence of blocks overlap one another by an amount that allows the complementary decoding processes to mitigate effects of the time-domain aliasing artifacts.

12. The apparatus of claim 9, wherein the first and second control parameters are assembled into the output signal and the overlap interval is greater than thirty-five seconds.

13. The apparatus of claim 9, wherein the first and second encoding processes are responsive to the first and second control parameters, respectively, and the overlap interval is greater than 4,500 milliseconds.

14. The apparatus of claim 9, wherein the threshold amount is such that differences in audio signals decoded from encoded audio information for the third block according to the first and second control parameters are imperceptible.

15. The apparatus of claim 9, wherein the first and second control parameters represent values of a factor used in a decoding process that is complementary to the first and second encoding processes, and wherein the threshold amount represents a change in the factor equal to 1 dB.

16. The apparatus of claim 9, wherein the first and second control parameters are represented by values that are quantized according to a quantization step size and the threshold amount is an integer number of quantization step sizes greater than or equal to zero.

17. A medium conveying a program of instructions that is executable by a device to perform a method for encoding a stream of audio information comprising audio samples arranged in a sequence of blocks, each block having a respective start and end, wherein a first block precedes a second block, a third block follows the second block, a fourth block immediately follows the third block, and a fifth block follows the fourth block, and wherein the method comprises:

(a) identifying first and second segments of the stream of audio information that overlap one another by an overlap interval, wherein

(1) the first segment comprises a plurality of blocks that starts with the first block and ends with the third block,

(2) the second segment comprises a plurality of blocks that starts with the second block, includes the fourth block, and ends with the fifth block, and

(3) the overlap interval extends from the start of the second block to the start of the fourth block;

(b) applying a first encoding process to the first segment of the stream of audio information to generate blocks of first encoded audio information and a first control parameter corresponding to blocks of audio samples up to and including the third block, wherein

(1) the first encoded audio information in a block is generated in response to a corresponding block of audio samples in the first segment of the stream of audio information up to and including the third block;

(2) the first control parameter in the block is generated in response to the corresponding block of audio samples and preceding blocks of audio samples in the first segment of the stream of audio information from the first block up to and including the third block, and

(c) applying a second encoding process to the second segment of the stream of audio information to generate blocks of second encoded audio information and a second control parameter corresponding to blocks of audio samples from the fourth block up to and including the fifth block, and to generate a second control parameter corresponding to audio samples in the third block, wherein

(1) the second encoded audio information in a block is generated in response to a corresponding block of audio samples in the second segment of the stream of audio information from the fourth block up to and including the fifth block,

(2) the second control parameter in the block is generated in response to the corresponding block of audio samples and preceding blocks of audio samples in the second segment of the stream of audio information from the second block up to and including the fifth block, and

(3) the overlap interval is such that a difference between values of the first and second control parameters for the third block is less than a threshold amount; and

(d) assembling the blocks of first and second encoded audio information into an output signal, wherein

(1) the first and second control parameters are assembled into the output signal, or

(2) the first encoding process generates the first encoded audio information in response to the first control parameter and the second encoding process generates the second encoded audio information in response to the second control parameter.

18. The medium according to claim 17, wherein the stream of audio information is arranged in frames, each frame having a plurality of blocks, the first, second and fourth blocks are beginning blocks in respective frames, and the third and fifth blocks are ending blocks in respective frames.

19. The medium according to claim 17, wherein the first and second encoding processes generate encoded audio information by applying filterbanks to the blocks of audio samples that cause time-domain aliasing artifacts to be generated by complementary decoding processes applied to the encoded audio information, and the blocks of audio samples in the sequence of blocks overlap one another by an amount that allows the complementary decoding processes to mitigate effects of the time-domain aliasing artifacts.

20. The medium of claim 17, wherein the first and second control parameters are assembled into the output signal and the overlap interval is greater than thirty-five seconds.

21. The medium of claim 17, wherein the first and second encoding processes are responsive to the first and second control parameters, respectively, and the overlap interval is greater than 4,500 milliseconds.

22. The medium of claim 17, wherein the threshold amount is such that differences in audio signals decoded from encoded audio information for the third block according to the first and second control parameters are imperceptible.

23. The medium of claim 17, wherein the first and second control parameters represent values of a factor used in a decoding process that is complementary to the first and second encoding processes, and wherein the threshold amount represents a change in the factor equal to 1 dB.

24. The medium of claim 17, wherein the first and second control parameters are represented by values that are quantized according to a quantization step size and the threshold amount is an integer number of quantization step sizes greater than or equal to zero.