US Patent 7305346 Audio processing method and audio processing apparatus

A volume adjustment unit reduces the volume of audio data. By coding the audio data where the volume is reduced in advance, the possibility of being decoded in a manner of exceeding the maximum bit number at a reproduction-side apparatus is reduced. Thus, the volume adjustment unit needs to reduce the volume of the audio data during a processing at a data input unit up to a quantization coding unit, that is, before the end of quantizing, based on a compression ratio.