AUDIO ENCODING DEVICE AND AUDIO ENCODING METHOD

• US 20090083041A1
• Filed: 04/27/2006
• Published: 03/26/2009
• Est. Priority Date: 04/28/2005
• Status: Active Grant

• Current Assignee: III Holdings 12, LLC (Intellectual Ventures LLC)
• Original Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Inventors: Yoshida, Koji
• Granted Patent: US 8,428,956 B2
• Time in Patent Office: Days
• US Class Current: 704/500
• 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

Abstract

There is provided an audio encoding device capable of effectively encoding a stereo audio even when a correlation between channels of the stereo audio is small. In the device, a monaural signal generation unit (110) generates a monaural signal by using a first channel signal and a second channel signal contained in the stereo signal. An encoding channel selection unit (120) selects one of the first channel signal and the second channel signal. An encoding unit including a monaural signal encoding unit (112), a first channel encoding unit (122), a second channel encoding unit (124), and a switching unit (126) encodes the generated monaural signal to obtain core-layer encoded data and encodes the selected channel signal to obtain extended layer encoded data corresponding to the core-layer encoded data.

Claims

1. A speech coding apparatus for encoding a stereo signal comprising a first channel signal and a second channel signal, the apparatus comprising:

a monaural signal generating section that generates a monaural signal using the first channel signal and the second channel signal;

a selecting section that selects one of the first channel signal and the second channel signal; and

a coding section that encodes the generated monaural signal to obtain core layer encoded data, and encodes the selected channel signal to obtain enhancement layer encoded data corresponding to the core layer encoded data.

2. The speech coding apparatus of claim 1, wherein:

the selecting section selects one of the first channel signal and the second channel signal every frame; and

the coding section encodes the monaural signal and the channel signal selected every frame, every frame.

3. The speech coding apparatus of claim 1, further comprising a calculating section that calculates a first coding distortion occurring when the first channel signal is selected and a second coding distortion occurring when the second channel signal is selected,

wherein the selecting section selects the first channel signal when the calculated first coding distortion is smaller than the calculated second coding distortion, and selects the second channel signal when the calculated second coding distortion is smaller than the calculated first coding distortion.

4. The speech coding apparatus of claim 3, wherein the coding section encodes the first channel signal and the second channel signal to obtain first coded data and second coded data, respectively, and outputs one of the first coded data and the second coded data corresponding to the selected channel signal as the enhancement layer encoded data, and comprises:

an estimation signal generating section that generates a second channel estimation signal corresponding to the second channel using a monaural decoded signal obtained when the coding section encodes the monaural signal and a first channel decoded signal obtained when the coding section encodes the first channel signal, and generates a first channel estimation signal corresponding to the first channel signal using the monaural decoded signal and a second channel decoded signal obtained when the coding section encodes the second channel signal; and

a distortion calculating section that calculates the first coding distortion based on error of the first channel decoded signal with respect to the first channel signal and error of the second channel estimation signal with respect to the second channel signal, and calculates second coding distortion based on error of the first channel estimation signal with respect to the first channel signal and error of the second channel decoding signal with respect to the second channel signal.

5. The speech coding apparatus of claim 1, wherein the selecting section comprises a calculating section that calculates a first intra-channel correlation corresponding to the first channel signal and a second intra-channel correlation corresponding to the second channel signal, and selects the first channel signal when the calculated first intra-channel correlation is greater than the calculated second intra-channel correlation, and selects the second channel signal when the calculated second intra-channel correlation is greater than the calculated first intra-channel correlation.

6. The speech coding apparatus of claim 1, wherein the coding section carries out code excited linear prediction coding of the first channel signal using a first adaptive codebook when the first channel signal is selected by the selecting section, obtains the enhancement layer encoded data using code excited linear prediction coding results and updates the first adaptive codebook using the code excited linear prediction coding results.

7. The speech coding apparatus of claim 6, wherein the coding section generates a second channel estimation signal corresponding to the second channel signal using the enhancement layer encoded data and a monaural decoded signal obtained when the monaural signal is encoded, and updates the second adaptive codebook used in code excited linear prediction coding of the second channel signal using an linear prediction coding prediction residual signal for the second channel estimation signal.

8. The speech coding apparatus of claim 7, wherein:

the selecting section correlates the first channel signal to a frame having a subframe and selects the first channel signal; and

the coding section obtains the enhancement layer encoded data for the frame while carrying out excitation search every subframe for the monaural signal and the first channel signal correlated with the frame and selected.

9. The speech coding apparatus of claim 8, wherein the coding section updates the first adaptive codebook per subframe and updates the second adaptive codebook per frame.

10. A mobile station apparatus comprising the speech coding apparatus of claim 1.

11. A base station apparatus comprising the speech coding apparatus of claim 1.

12. A speech coding method for encoding a stereo signal comprising a first channel signal and a second channel signal, comprising the steps of:

generating a monaural signal using the first channel signal and the second channel signal;

selecting one of the first channel signal and the second channel signal; and

encoding a generated monaural signal to obtain core layer encoded data and encoding a selected channel signal to obtain enhancement layer encoded data corresponding to the core layer encoded data.