Apparatus and method for coding audio data based on input signal distribution characteristics of each channel
View Patent ↗Provided is an audio coding apparatus and method that can selectively apply a operation mode of a coding module for stereo or multi-channel representation according to input signal characteristics of each channel, when voice or music signals are transmitted using an audio codec in portable terminals capable of stereo or multi-channel input and output. The audio coding apparatus includes a down-mixer for down-mixing multi-channel audio signals into mono signals; a coder for coding the mono signals; an input channel correlation analyzer for deciding whether to give them stereo effect based on their signal distribution characteristics, and outputting a control signal indicating whether to perform stereo representation process; and a stereo representation unit for performing stereo representation process onto the multi-channel audio signals when the control signal indicating to perform stereo representation process.
1. An apparatus for coding audio signals based on signal distribution characteristics of each channel, comprising:
a down-mixer for receiving multi-channel audio signals and down-mixing the multi-channel audio signals into mono signals;
a coder for coding the mono signals;
an input channel correlation analyzer for receiving the multi-channel audio signals, deciding whether to give stereo effect to the multi-channel audio signals based on signal distribution characteristics of the multi-channel audio signals for each channel, and outputting a control signal indicating whether to perform stereo representation process; and
a stereo representation unit for performing stereo representation process onto the multi-channel audio signals when the control signal indicating to perform stereo representation process,
wherein the input channel correlation analyzer includes:
an auto-correlation calculator for calculating and outputting auto-correlation for the multi-channel audio signals;
a cross-correlation calculator for calculating and outputting cross-correlation for the multi-channel audio signals;
a correlation ratio calculator for receiving the auto-correlation and the cross-correlation, calculating a ratio between the auto-correlation and the cross-correlation, and outputting a correlation ratio; and
a stereo coding decider for comparing the correlation ratio with a predetermined threshold and deciding whether to inactivate operation of a stereo representation unit,
wherein the stereo coding decider generates and outputs a control signal including information for inactivating operation of the stereo representation unit when the correlation ratio is smaller than the threshold, and the stereo coding decider generates and outputs a control signal including information for operating the stereo representation unit when the correlation ratio is not smaller than the threshold.
2. A method for coding audio signals based on signal distribution characteristics of each channel, comprising:
receiving multi-channel audio signals;
down-mixing the multi-channel audio signals into mono signals;
coding the mono signals; and
deciding whether to give stereo effect to the multi-channel audio signals based on signal distribution characteristics of each channel,
wherein deciding whether to give stereo effect to the multi-channel audio signals includes:
calculating auto-correlation for the multi-channel audio signals;
calculating cross-correlation for the multi-channel audio signals;
acquiring a correlation ratio by calculating a ratio between the auto-correlation and the cross-correlation;
comparing the correlation value with a predetermined threshold; and
deciding whether to perform stereo representation.
3. The method of claim 2 , wherein deciding whether to give stereo effect to the multi-channel audio signals includes:
generating and outputting a control signal including information for holding the stereo representation process when the correlation ratio is smaller than the threshold; and
generating and outputting a control signal including information for performing the stereo representation process when the correlation ratio is not smaller than the threshold.
4. The method of claim 3 , wherein the multi-channel audio signals are stereo voice signals.