Adaptive vector Huffman coding and decoding based on a sum of values of audio data symbols

• US 7,822,601 B2
• Filed: 05/16/2008
• Issued: 10/26/2010
• Est. Priority Date: 09/04/2002
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Chen, Wei-Ge, Mehrotra, Sanjeev
• Primary Examiner(s): Lerner; Martin
• Application Number:
  US12/122,553
• Publication Number:
  US 20080262855A1
• Time in Patent Office: 893 Days
• Field of Search: 704/222, 704/230, 704/500, 341/65, 341/67, 341/51
• US Class Current: 704/222
• CPC Class Codes: G10L 19/032 Quantisation or dequantisation of spectral components
• CPC Class Codes: H03M 7/40 Conversion to or from variable length codes, e.g. Shannon-Fano code, Huffman code, Morse code
• CPC Class Codes: H03M 7/4006 Conversion to or from arithmetic code
• CPC Class Codes: H03M 7/4093 Variable length to variable length coding
• CPC Class Codes: H03M 7/46 Conversion to or from run-length codes, i.e. by representing the number of consecutive digits, or groups of digits, of the same kind by a code word and a digit indicative of that kind

Abstract

An audio encoder performs entropy encoding of audio data. For example, an audio encoder determines a Huffman code from a Huffman code table to use for encoding a vector of audio data symbols, where the determining is based on a sum of values of the audio data symbols. An audio decoder performs corresponding entropy decoding.

Claims

1. In a computer system that implements an audio encoder, a method of encoding audio data in a vector Huffman encoding scheme, the method comprising:

by the computer system that implements the audio encoder;

determining a Huffman code from a Huffman code table to use for encoding a vector of audio data symbols, wherein the determining is based on a sum of values of the audio data symbols in the vector, wherein the determining comprises comparing the sum of values with a threshold, and wherein the Huffman code table contains Huffman codes for vectors of audio data symbols whose sum is less than the threshold and an escape code for vectors of audio data symbols whose sum is greater than the threshold; and

encoding the vector of audio data symbols using the Huffman code.

2. The method of claim 1 wherein the Huffman code is the escape code, wherein the vector of audio data symbols is an n-dimension vector, wherein n is greater than 1, and wherein the escape code indicates that the n-dimension vector is to be encoded as x n/x-dimension vectors using at least one different Huffman code table.

3. The method of claim 1 wherein the threshold depends on a number of audio data symbols in the vector.

4. The method of claim 3 wherein the number of audio data symbols is 4, and wherein the threshold is 6.

5. The method of claim 3 wherein the number of audio data symbols is 2, and wherein the threshold is 16.

6. The method of claim 3 wherein the number of audio data symbols is 1, and wherein the threshold is 100.

7. In a computer system that implements an audio decoder, a method of decoding audio data in a vector Huffman decoding scheme, the method comprising:

by the computer system that implements the audio decoder;

receiving a Huffman code to use for decoding a vector of audio data symbols, the Huffman code having been determined and selected from a Huffman code table during encoding based on a sum of values of the audio data symbols in the vector, wherein the Huffman code depends at least in part on results of comparing the sum of values with a threshold during the encoding, and wherein the Huffman code table contains Huffman codes for vectors of audio data symbols whose sum is less than the threshold and an escape code for vectors of audio data symbols whose sum is greater than the threshold; and

decoding the vector of audio data symbols using the Huffman code.

8. The method of claim 7 wherein the Huffman code is the escape code, wherein the vector of audio data symbols includes plural audio data symbols, and wherein the escape code indicates that the vector of audio data symbols is to be decoded using one or more other Huffman codes from one or more other Huffman code tables.

9. The method of claim 7, wherein the threshold depends on a number of audio data symbols in the vector.

10. The method of claim 9 wherein the number of audio data symbols is 4, and wherein the threshold is 6.

11. The method of claim 9 wherein the number of audio data symbols is 2, and wherein the threshold is 16.

12. The method of claim 9 wherein the number of audio data symbols is 1, and wherein the threshold is 100.

13. A storage medium storing computer-executable instructions for causing an audio decoder to perform the method of claim 7.

14. A storage medium storing computer-executable instructions for causing a computer system programmed thereby to perform a method of encoding audio data in a vector Huffman encoding scheme, the method comprising:

determining a Huffman code from a Huffman code table to use for encoding a vector of audio data symbols, wherein the determining is based on a sum of values of the audio data symbols in the vector, wherein the determining comprises comparing the sum of values with a threshold, and wherein the Huffman code table contains Huffman codes for vectors of audio data symbols whose sum is less than the threshold and an escape code for vectors of audio data symbols whose sum is greater than the threshold; and

encoding the vector of audio data symbols using the Huffman code.

15. The storage medium of claim 14 wherein the Huffman code is the escape code, wherein the vector of audio data symbols is an n-dimension vector, wherein n is greater than 1, and wherein the escape code indicates that the n-dimension vector is to be encoded as x n/x-dimension vectors using at least one different Huffman code table.

16. The storage medium of claim 14 wherein the threshold depends on a number of audio data symbols in the vector.

17. The storage medium of claim 16 wherein the number of audio data symbols is 4, and wherein the threshold is 6.

18. The storage medium of claim 16 wherein the number of audio data symbols is 2, and wherein the threshold is 16.

19. The storage medium of claim 16 wherein the number of audio data symbols is 1, and wherein the threshold is 100.