Reduced complexity transform for a low-frequency-effects channel

• US 10,410,644 B2
• Filed: 03/19/2012
• Issued: 09/10/2019
• Est. Priority Date: 03/28/2011
• Status: Active Grant

• Current Assignee: Dolby Laboratories Licensing Corporation (Dolby Laboratories Incorporated)
• Original Assignee: Dolby Laboratories Licensing Corporation (Dolby Laboratories Incorporated)
• Inventors: Fellers, Matthew C.
• Primary Examiner(s): Saint Cyr, Leonard
• Application Number:
  US14/005,924
• Publication Number:
  US 20140012588A1
• Time in Patent Office: 2,731 Days
• Field of Search: 704204, 704205
• CPC Class Codes: G06F 17/147 Discrete orthonormal transforms, e.g. discrete cosine transform, discrete sine transform, and variations therefrom, e.g. modified discrete cosine transform, integer transforms approximating the discrete cosine transform G06F17/145 takes precedence
• CPC Class Codes: G10L 19/008 Multichannel audio signal coding or decoding using interchannel correlation to reduce redundancy, e.g. joint-stereo, intensity-coding or matrixing
• CPC Class Codes: G10L 19/02 using spectral analysis, e.g. transform vocoders or subband vocoders
• CPC Class Codes: G10L 19/0212 using orthogonal transformation

Abstract

The computational resources that are needed to apply a transform-based filterbank to a limited-bandwidth audio signals are reduced by performing an integrated process of combining real-valued input data into complex-valued data and applying a short transform to the complex-valued data, applying a bank of very short transforms to the output of the integrated process, and deriving a sequence of real-valued output data from the outputs of the bank of very short transforms.

Claims

1. A method performed by an audio signal processing device, for decoding an encoded digital audio signal, wherein the method comprises:

receiving, by the audio signal processing device, the encoded digital audio signal;

decoding, by the audio signal processing device, the received encoded digital audio signal to generate a block of real-valued transform coefficients, wherein the block has a quantity K of real-valued transform coefficients of which only a number L of the real-valued transform coefficients represent spectral components of a limited-bandwidth audio signal, ½

L<

M<

K, and M is a power of two;

transforming, by the audio signal processing device, the block of real-valued transform coefficients to generate a sequence of N real-valued signal samples representing temporal components of the limited-bandwidth audio signal, wherein N=2·

K; and

outputting, by the audio signal processing device, the real-valued signal samples representing temporal components of the limited-bandwidth audio signal;

wherein the transforming comprises;

applying, by the audio signal processing device, a first-transform of length R to either the L real-valued transform coefficients representing spectral components of the limited-bandwidth audio signal, or complex-valued coefficients derived from the L real-valued transform coefficients representing spectral components of the limited-bandwidth audio signal, wherein

2. The method of claim 1, wherein:

each of the second transforms is equivalent to performing calculations expressed as

3. The method of claim 1, wherein the first transform is equivalent to performing calculations expressed as

4. The method of claim 1, wherein the first transform is equivalent to performing calculations expressed as

5. The method of claim 1, wherein the first transform is equivalent to performing calculations expressed as

6. The method of claim 1, further comprising generating the limited-bandwidth audio signal using the real-valued signal samples.

7. An audio signal processing device for decoding an encoded digital audio signal, wherein the audio signal processing device comprises one or more processors configured to:

receive the encoded digital audio signal

decode the received encoded digital audio signal to generate a block of real-valued transform coefficients, wherein the block has a quantity K of real-valued transform coefficients of which only a number L of the real-valued transform coefficients represent spectral components of a limited-bandwidth audio signal, ½

L<

M<

K, and M is a power of two;

transform the block of real-valued transform coefficients to generate a sequence of N real-valued signal samples representing temporal components of the limited-bandwidth audio signal, wherein N=2·

K, and

outputting the real-valued signal samples representing temporal components of the limited-bandwidth audio signal;

wherein the transforming comprises;

applying a first-transform of length R to either the L real-valued transform coefficients representing spectral components of the limited-bandwidth audio signal, or complex-valued coefficients derived from the L real-valued transform coefficients representing spectral components of the limited-bandwidth audio signal, wherein

8. The audio signal processing device of claim 7, wherein:

each of the second transforms is equivalent to performing calculations expressed as

9. The audio signal processing device of claim 7, wherein the first transform is equivalent to performing calculations expressed as

10. The audio signal processing device of claim 7, wherein the first transform is equivalent to performing calculations expressed as

11. The audio signal processing device of claim 7, wherein the first transform is equivalent to performing calculations expressed as

12. A non-transitory medium recording a program of instructions that is executable by an audio signal processing device, wherein the program of instructions cause the audio signal processing device to perform a method for decoding an encoded digital audio signal, wherein the method comprises:

receiving, by the audio signal processing device, the encoded digital audio signal;

decoding, by the audio signal processing device, the received encoded digital audio signal to generate a block of real-valued transform coefficients, wherein the block has a quantity K of real-valued transform coefficients of which only a number L of the real-valued transform coefficients represent spectral components of a limited-bandwidth audio signal, ½

L<

M<

K, and M is a power of two;

transforming, by the audio signal processing device, the block of real-valued transform coefficients to generate a sequence of N real-valued signal samples representing temporal components of the limited-bandwidth audio signal, wherein N=2·

K; and

outputting, by the audio signal processing device, the real-valued signal samples representing temporal components of the limited-bandwidth audio signal;

wherein the transforming comprises;

applying, by the audio signal processing device, a first-transform of length R to either the L real-valued transform coefficients representing spectral components of the limited-bandwidth audio signal, or complex-valued coefficients derived from the L real-valued transform coefficients representing spectral components of the limited-bandwidth audio signal, wherein

13. The medium of claim 12, wherein:

each of the second transforms is equivalent to performing calculations expressed as

14. The medium of claim 12, wherein the first transform is equivalent to performing calculations expressed as

15. The medium of claim 12, wherein the first transform is equivalent to performing calculations expressed as

16. The medium of claim 12, wherein the first transform is equivalent to performing calculations expressed as