Coding with improved time resolution for selected segments via adaptive block transformation of a group of samples from a subband decomposition

• US 20070016405A1
• Filed: 07/15/2005
• Published: 01/18/2007
• Est. Priority Date: 07/15/2005
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Chen, Wei-Ge, Mehrotra, Sanjeev, Malvar, Henrique
• Granted Patent: US 7,546,240 B2
• Time in Patent Office: Days
• US Class Current: 704/203
• CPC Class Codes: G10L 19/0212 using orthogonal transformation
• CPC Class Codes: G10L 19/025 Detection of transients or attacks for time/frequency resolution switching

Abstract

A transform coder is described that performs a time-split transform in addition to a discrete cosine type transform. A time-split transform is selectively performed based on characteristics of media data. Transient detection identifies a changing signal characteristic, such as a transient in media data. After encoding an input signal from a time domain to a transform domain, a time-splitting transformer selectively perform an orthogonal sum-difference transform on adjacent coefficients indicated by a changing signal characteristic location. The orthogonal sum-difference transform on adjacent coefficients results in transforming a vector of coefficients in the transform domain as if they were multiplied by an identity matrix including at least one 2×2 time-split block along a diagonal of the matrix. A decoder performs an inverse of the described transforms.

Claims

1. A transform coder comprising:

a changing signal characteristic detection component operating to identify a changing signal characteristic location;

an encoding component transforms an input signal from a time domain to a transform domain; and

a time-splitting transformer component operating in response to the identified changing signal characteristic location to selectively perform an orthogonal sum-difference transform on adjacent coefficients indicated by the identified changing signal characteristic location.

2. The transform coder of claim 1 wherein the orthogonal sum-difference transform on adjacent coefficients results in transforming a vector of coefficients in the transform domain as if they were multiplied by an identity matrix with at least one 2×

2 block along a diagonal of the matrix, where the at least one 2×

2 block comprises orthogonally transformational properties substantially similar to one of the following 2×

2 blocks;

$c*\left(\begin{array}{cc}1& 1\\ 1& -1\end{array}\right)$ $c*\left(\begin{array}{cc}1& 1\\ -1& 1\end{array}\right)$

where c is a scale factor.

3. The transform of claim 1 wherein the time-splitting transformer component encodes side information indicating that there are no time-splits in at least one sub-frame.

4. The transform coder of claim 1 further comprising:

a window configuration component operating in response to the identified changing signal characteristic location to configure a first configuration of window sizes selected from at least a small window size and a large window size, so as to place one or more windows of the small window size to encompass a region of the input signal having at least one identified changing signal characteristic location and place windows of the large window size in areas of the input signal having no identified changing signal characteristic locations;

the encoding component further inverse-transforming to produce a reconstructed version of the input signal;

a quality measurement component operating to measure achieved quality of the reconstructed signal; and

the window configuration component operating in response to the achieved quality measurement to adjust sizes of the first configuration of window sizes according to the achieved quality measurement to produce a second configuration window sizes.

5. The transform coder of claim 4 wherein:

the quality measurement component further operates to measure achieved perceptual quantization noise of the reconstructed signal for at least some of the windows in the first configuration; and

the window configuration component further operates to increase a window size where the measure of achieved perceptual quantization noise exceeds an acceptable threshold.

6. The transform coder of claim 4 wherein:

the quality measurement component further operates to detect pre-echo in the reconstructed signal; and

the window configuration component further operates to decrease at least one window where pre-echo is detected.

7. The transform coder of claim 2 wherein the transform coder outputs side information identifying where the orthogonal sum-difference transform was performed.

8. A transform decoder that performs the corresponding inverse steps to recover data coded by the transform coder of claim 7.

9. A transform decoder comprising:

an inverse time-splitting transformer component receives side information and coefficient data in a transform domain and selectively performs an inverse orthogonal sum-difference transformation on adjacent coefficients indicated in received side information; and

after the inverse time-splitting transformer component performs an inverse orthogonal sum-difference transformation, an inverse transformer transforms coefficient data from the transform domain to a time domain.

10. The transform decoder of claim 9 wherein the transform decoder outputs reconstructed audio samples.

11. The transform decoder of claim 9 further comprising:

an inverse window configuration component receives side information about window and sub-frame sizes; and

the inverse transformer transforms coefficient data according to the window and sub-band sizes.

12. The transform decoder of claim 9 wherein the inverse orthogonal sum-difference transformation on adjacent coefficients results in transforming a vector of coefficients in the transform domain as if it were multiplied by an inverse of a time-splitting transform used to code the vector of coefficients.

13. The transform decoder of claim 9 wherein the inverse time-splitting transformer component receives side information indicating that an inverse selectively applied sum-difference of adjacent coefficients orthogonal transform should be applied to at least one pair of adjacent coefficients in a vector X in the transform domain, where there are M coefficients in vector X that are uniquely identified as X[k] with k an integer ranging from 0 to M−

1, so that the pair of adjacent coefficients is of the form {X[2r], X[2r+1]}, where r is an integer.

14. The transform decoder of claim 9 wherein the inverse time-splitting transformer component receives side information indicating that there are no time-splits in at least one sub-frame.

15. The transform decoder of claim 9 wherein the inverse time-splitting transformer component receives side information indicating whether or not there is a time-split in an extended band.

16. A method of decoding comprising:

receiving side information and coefficient data in a transform domain;

selectively performing an inverse time-split transform on adjacent coefficients as indicated in received side information; and

performing an inverse transform on received coefficient data comprising transforming the coefficient data from the transform domain to a time domain.

17. The method of claim 16 further comprising:

identifying sub-frame sizes in received side information; and

wherein the inverse transform is performed according to the identified sub-frame sizes.

18. The method of claim 16 wherein selectively performing the inverse time-split transform comprises determining from the side information whether there is a time-split in a sub-band.

19. The method of claim 16 wherein selectively performing the inverse time-split transform comprises determining from side information whether or not there is a time-split in each sub-band in an extended band.

20. The method of claim 16 wherein selectively performing the inverse time-split transform comprises determining from side information a pair of adjacent coefficients in a transform domain on which to perform an inverse sum-difference transform.