METHOD AND APPARATUS FOR ENCODING AUDIO SIGNAL AND METHOD AND APPARATUS FOR DECODING AUDIO SIGNAL

• US 20080235034A1
• Filed: 01/30/2008
• Published: 09/25/2008
• Est. Priority Date: 03/23/2007
• Status: Active Grant

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: LEE, Nam-suk, LEE, Chul-woo, JEONG, Jong-hoon, OH, Jae-one, LEE, Geon-hyoung
• Granted Patent: US 8,024,180 B2
• Time in Patent Office: Days
• US Class Current: 704/500
• CPC Class Codes: G10L 19/093 using sinusoidal excitation models

Abstract

Provided are a method and apparatus for encoding an audio signal to efficiently encode a harmonic envelope and a method and apparatus for decoding an audio signal to decode the harmonic envelope. The method of encoding an audio signal includes performing harmonic analysis with respect to an input signal to determine harmonic parameters with respect to harmonic signals; regarding amplitudes of the harmonic signals included in the harmonic parameters as signals in the time domain so as to perform time-frequency transformation; and encoding the time-frequency transformed values. When expressing a harmonic envelope, the amplitudes of the harmonic signals are regarded as signals in the time domain so as to perform a time-frequency transformation and only a part from among the transformed values is selected to be encoded. Therefore, sound quality is not affected and coding efficiency greatly improves.

Claims

1. A method of encoding an audio signal, the method comprising:

performing harmonic analysis with respect to an input signal to determine harmonic parameters with respect to harmonic signals;

performing a time-frequency transformation by regarding amplitudes of harmonic signals included in the harmonic parameters as signals in a time domain, to generate time-frequency transformed values; and

encoding the time-frequency transformed values.

2. The method of claim 1, wherein the performing the time-frequency transformation comprises:

numbering the harmonic signals sequentially starting from a lowest frequency; and

performing a time-frequency transformation with respect to the amplitudes of the harmonic signals by regarding the numbering of the harmonic signals as frame numbers of the signal in the time domain.

3. The method of claim 1, wherein the encoding the time-frequency transformed values comprises:

selecting a predetermined number of values from among the time-frequency transformed values from a low frequency region; and

encoding the selected predetermined number of values.

4. The method of claim 1, wherein the time-frequency transformation is one of Discrete Cosine Transformation (DCT), Modified Discrete Cosine Transformation (MDCT), and Fast Fourier Transformation (FFT).

5. The method of claim 1, wherein the harmonic parameters comprise frequency, amplitude, and phase of the harmonic signals.

6. The method of claim 1, wherein the harmonic parameters comprise amplitude of a sinusoidal signal having a frequency with a predetermined correction value for a multiple frequency of a fundamental frequency signal.

7. An apparatus for encoding an audio signal, the apparatus comprising:

a harmonic analyzing unit, which performs a harmonic analysis with respect to an input signal and determines harmonic parameters with respect to harmonic signals;

a time-frequency transforming unit, which performs a time-frequency transformation by regarding amplitudes of harmonic signals included in the harmonic parameters as signals in a time domain, to generate time-frequency transformed values; and

a transformed value encoding unit which encodes the time-frequency transformed values.

8. The apparatus of claim 7, wherein the time-frequency transforming unit numbers the harmonic signals sequentially starting from a lowest frequency and performs a time-frequency transformation by regarding the numbers of the harmonic signals as frame numbers of the signal in the time domain.

9. The apparatus of claim 7, wherein the transformed value encoding unit selects a predetermined number of values from among the time-frequency transformed values from a low frequency region and encodes the selected predetermined number of values.

10. The apparatus of claim 7, wherein the time-frequency transformation is one of Discrete Cosine Transformation (DCT), Modified Discrete Cosine Transformation (MDCT), and Fast Fourier Transformation (FFT).

11. The apparatus of claim 7, wherein the harmonic parameters comprise frequency, amplitude, and phase of the harmonic signals.

12. The apparatus of claim 7, wherein the harmonic parameters comprise amplitude of a sinusoidal signal having a frequency with a predetermined correction value for a multiple frequency of a fundamental frequency signal.

13. A method of decoding an audio signal, the method comprising:

decoding encoded data to determine time-frequency transformed values;

applying an inverse time-frequency transformation to the time-frequency transformed values so as to determine amplitudes of harmonic signals in a time domain; and

determining the amplitudes of the harmonic signals in a frequency region by regarding the harmonic signals in the time domain as signals in the frequency region.

14. The method of claim 13, wherein the determining the amplitudes of the harmonic signals comprises:

sequentially numbering the harmonic signals in the time domain; and

determining a value, obtained by multiplying a fundamental frequency by a number of the numbered harmonic signals, as a frequency of the harmonic signal that corresponds to the amplitudes.

15. The method of claim 13, wherein the time-frequency transformation is one of Discrete Cosine Transformation (DCT), Modified Discrete Cosine Transformation (MDCT), and Fast Fourier Transformation (FFT).

16. An apparatus for decoding an audio signal, the apparatus comprising:

a decoding unit, which decodes encoded data and determines time-frequency transformed values;

a time-frequency inverse-transforming unit, which applies an inverse time-frequency transformation to the time-frequency transformed values so as to determine amplitudes of harmonic signals in a time domain; and

a frequency region signal regarding unit, which determines the amplitudes of the harmonic signals in a frequency region by regarding the harmonic signals in the time domain as signals in the frequency region.

17. The apparatus of claim 16, wherein the frequency region signal regarding unit sequentially numbers the harmonic signals in the time domain and determines a value, obtained by multiplying a fundamental frequency by a number of the numbered harmonic signals, as a frequency of the harmonic signal that corresponds to the amplitudes.

18. The apparatus of claim 16, wherein the time-frequency transformation is one of Discrete Cosine Transformation (DCT), Modified Discrete Cosine Transformation (MDCT), and Fast Fourier Transformation (FFT).

19. A computer readable recording medium having embodied thereon a computer program for executing a method comprising:

performing harmonic analysis with respect to an input signal to determine harmonic parameters with respect to harmonic signals;

performing a time-frequency transformation by regarding amplitudes of harmonic signals included in the harmonic parameters as signals in a time domain, to generate time-frequency transformed values; and

encoding the time-frequency transformed values.

20. A computer readable recording medium having embodied thereon a computer program for executing a method comprising:

decoding encoded data to determine time-frequency transformed values;

applying an inverse time-frequency transformation to the time-frequency transformed values so as to determine amplitudes of harmonic signals in a time domain; and

determining the amplitudes of the harmonic signals in a frequency region by regarding the harmonic signals in the time domain as signal in a frequency region.