Audio encoding device and audio encoding method
There is provided an audio encoding device capable of effectively encoding stereo audio in audio encoding having monaural-stereo scalable configuration. In this device, a correlation degree comparison unit ( 304 ) calculates correlation in a first channel (correlation degree between the past signal and the current signal in the first channel) from the first channel audio signal and calculates correlation in a second channel (correlation degree between the past signal and the current signal in the second channel) from the second channel audio signal. The correlation in the first channel is compared to the correlation in the second channel. A channel having the greater correlation is selected. According to the selection result of a correlation comparison unit ( 304 ), a selection unit ( 305 ) selects the first channel prediction signal outputted from a first channel prediction unit ( 307 ) or the first channel prediction signal outputted from a first channel signal generation unit ( 311 ) and outputs the selected signal to a subtractor ( 303 ) and a first channel prediction residual signal encoding unit ( 308 ).
1. A speech coding apparatus, comprising:
a first coder, comprising a processor, that carries out core layer coding for a monaural signal;
a second coder that carries out enhancement layer coding for a stereo signal;
a correlation comparator that calculates a first intra-channel correlation corresponding to a first single channel signal and a second intra-channel correlation corresponding to a second single channel signal, compares the first intra-channel correlation and the second intra-channel correlation, the first single channel signal and the second single channel signal constituting the stereo signal, and
the correlation comparator selects a first channel of the first single channel signal if the first intra-channel correlation is greater than the second intra-channel correlation, and selects a second channel of the second single channel signal if the second intra-channel correlation is greater than the first intra-channel correlation, and
an outputter that outputs encoded data so that the encoded data is transmitted to a speech decoding apparatus,
wherein:
the first coder generates a monaural signal from the first channel signal and the second channel signal;
the second coder carries out coding of the first channel using a prediction signal generated by an intra-channel prediction of the channel selected by the correlation comparator; and
the encoded data includes selection information representing the channel selected by the correlation comparator, data coded by the second coder and data coded by the first coder.
2. The speech coding apparatus of claim 1 , wherein, when the second channel has greater channel correlation, the second coder predicts the first single channel signal from a prediction signal generated by an intra-channel prediction of the second channel and the monaural signal.
3. A wireless communication mobile station apparatus comprising the speech coding apparatus of claim 1 .
4. A wireless communication base station apparatus comprising the speech coding apparatus of claim 1 .
5. A speech encoding method for carrying out core layer coding for a monaural signal and enhancement layer coding for a stereo signal, the method comprising:
in the core layer, generating a monaural signal from a first single channel signal and a second single channel signal constituting a stereo signal;
in the enhancement layer, calculating a first intra-channel correlation corresponding to the first single channel signal and a second intra-channel correlation corresponding to the second single channel signal, comparing the first intra-channel correlation and the second intra-channel correlation, selecting a first channel of the first single channel signal if the first intra-channel correlation is greater than the second intra-channel correlation, and selecting a second channel of the second single channel signal if the second intra-channel correlation is greater than the first intra-channel correlation, and carrying out coding of the first channel using a prediction signal generated by an intra-channel prediction of the selected channel having greater intra-channel correlation; and
outputting encoded data so that the encoded data is transmitted to a speech decoding apparatus,
wherein:
the encoded data includes selection information representing the selected channel, data coded in the core layer and data coded in the enhancement layer.