Stereo acoustic signal encoding apparatus, stereo acoustic signal decoding apparatus, and methods for the same
Disclosed is a stereo acoustic signal encoding apparatus in which the signal quality does not deteriorate if there are a plurality of sound sources. A peak tracing unit ( 401 ) splits frames of a right channel signal and a left channel signal into a plurality of sub frames; detects the peaks of wave shapes of the split sub frames; and estimates a frame delay time D for each frame of the right channel signal and the left channel signal by comparing the positions of the detected peaks. A time adjusting unit ( 402 ) adjusts the time of the right channel signal on the basis of the frame time delay D. A down-mix operation is carried out using the right channel signal which has been subjected to the time adjustment and the left channel signal to generate a mono signal and a sub signal. A mono signal encoding unit ( 403 ) encodes the mono signal. A sub signal encoding unit ( 404 ) encodes the sub signal. The time delay encoding unit ( 405 ) encodes the frame time delay D.
1. A stereo acoustic sound signal encoding apparatus comprising:
a peak tracking section that detects peaks in waveforms of a plurality of sub frames obtained by dividing a frame of a right channel signal and a left channel signal, checks on a validity of a first frame time delay of the frame of the right channel signal and the left channel signal by comparing the first frame time delay with subframe time delays of the plurality of sub frames calculated using the detected peaks, and obtains a second frame time delay on the basis of the checked result;
a time alignment section that performs time alignment on one of the right channel signal and the left channel signal on the basis of the second frame time delay; and
an encoding section that encodes (i) the other of the right channel signal and the left channel signal besides the time-aligned one of the right channel signal and the left channel signal, (ii) the time-aligned one of the right channel signal and the left channel signal, and (iii) the second frame time delay.
2. The stereo acoustic sound signal encoding apparatus according to claim 1 , wherein the peak tracking section regards the first frame time delay as invalid in a case where the number of sub frames, in each of which a difference between the first frame time delay and the sub-frame time delay is equal to or more than a predetermined value, is equal to or more than a threshold value.
3. The stereo acoustic sound signal encoding apparatus according to claim 2 , wherein the peak tracking section outputs, as the second frame time delay, one of zero, a third frame time delay of a previous frame, or a fourth frame time delay that is an average of frame time delays of previous frames.
4. The stereo acoustic sound signal encoding apparatus according to claim 1 , wherein the peak tracking section estimates the first frame time delay using peaks other than peaks of the sub frames in which the values of the peaks are smaller than a threshold value.
5. The stereo acoustic sound signal encoding apparatus according to claim 1 , wherein the peak tracking section outputs the first frame time delay as the second frame time delay in a case where the number of sub frames, in each of which a difference between the first frame time delay and the sub-frame time delay is equal to or more than a predetermined value, is less than a threshold value.
6. The stereo acoustic sound signal encoding apparatus according to claim 1 , wherein:
the time alignment section performs time alignment on both of the right channel signal and the left channel signal on the basis of the second frame time delay; and
the encoding section encodes the time-aligned right channel signal, the time-aligned left channel signal, and the frame time delay.
7. The stereo acoustic sound signal encoding apparatus according to claim 1 , wherein the peak tracking section estimates the first frame time delay using the detected peaks.
8. The stereo acoustic sound signal encoding apparatus according to claim 1 , further comprising a time delay estimation section that estimates the first frame time delay by a method different from a method estimating the first frame time delay using the detected peaks.
9. A stereo acoustic sound signal decoding apparatus comprising:
a separation section that separates a bit stream into a right channel signal, a left channel signal, and a frame time delay, the bit stream generated by detecting peaks in waveforms of a plurality of sub frames obtained by dividing a frame of the right channel signal and the right channel signal, checking on a validity of a first frame time delay of each frame of the right channel signal and the left channel signal by comparing the first frame time delay with sub frame time delays of the plurality of sub frames calculated using the detected peaks, obtaining a second frame time delay on the basis of the checked result, performing time alignment on one of the right channel signal and the left channel signal on the basis of the second frame time delay, and encoding and multiplexing (i) the other of the right channel signal and the left channel signal besides the time-aligned one of the right channel signal and the left channel signal,(ii) the time-aligned one of the right channel signal and the left channel signal, and (iii) the frame time delay;
a decoding section that decodes the separated right channel signal, the separated left channel signal, and the separated frame time delay; and
a time restoring section that restores the right channel signal to a time before the time alignment, on the basis of the separated frame time delay.
10. A stereo acoustic sound signal encoding method comprising:
detecting peaks in waveforms of a plurality of sub frames obtained by dividing a frame of a right channel signal and a left channel signal;
checking on the validity of a first frame time delay of the frame of the right channel signal and the left channel signal by comparing the first frame time delay with subframe time delays of the plurality of sub frames calculated using the detected peaks, and obtaining a second frame time delay on the basis of the checked result;
performing time alignment on one of the right channel signal and the left channel signal on the basis of the frame time delay; and
encoding (i) the other of the right channel signal and the left channel signal, besides the time-aligned one of the right channel signal and the left channel signal, and (ii) the time-aligned one of the right channel signal and the left channel signal, and (iii) the second frame time delay.
11. A stereo acoustic sound signal decoding method comprising:
separating a bit stream into a right channel signal, a left channel signal, and a frame time delay, the bit stream generated by detecting peaks in waveforms of a plurality of sub frames obtained by dividing a frame of the right channel signal and the right channel signal, checking on a validity of a first frame time delay of each frame of the right channel signal and the left channel signal by comparing the first frame time delay with sub frame time delays of the plurality of sub frames calculated using the detected peaks, obtaining a second frame time delay on the basis of the checked result, performing time alignment on one of the right channel signal and the left channel signal on the basis of the second frame time delay, and encoding and multiplexing (i) the other of the right channel signal and the left channel signal besides the time-aligned one of the right channel signal and the left channel signal, (ii) the time-aligned one of the right channel signal and the left channel signal, and (iii) the second frame time delay;
decoding the separated right channel signal, the separated left channel signal, and the separated frame time delay; and
restoring the right channel signal to a time before the time alignment, on the basis of the separated frame time delay.