To encode the multichannel signals with high efficiency.

A mixer 102 produces the mixture processing data based on the audio data supplied through the input terminals 101a to 101e, and these processing data are supplied to the processing data extractors 103a to 103e and the encoders 105f and 105g respectively. The extractors 103a to 103e supply the data which are not reproduced by the mixture processing data to the encoders 105a to 105e, and the reproduction parameters of other data which are reproduced by the mixture processing data are supplied to a multiplexer 106. The reproduction parameters and the data which are encoded by the encoders 105a to 105g are turned into a bit stream by the multiplexer 106 and then outputted.