To reduce a deterioration in sound quality of audio data, which occurs when the audio data once subjected to compression processing are once expanded to apply the compression processing again.
The multiplexed audio data formed by compressing the audio data by a first compression system and by multiplexing the data together with parameters necessary for expansion processing are separated by reverse multiplexing into the quantized audio data and the parameters necessary for the expansion processing. The multiplexed data complying with the format of a second compression system are formed by respectively converting the encoded audio data and the parameter data to the data complying with the formation of the second compression system and multiplexing the data as it is.
Tomoyasu Sakaguchi
Hiroki Naito