In other words, when a multi-channel audio signal coded by the sub-band coding method or multimedia data including a multi-channel audio signal coded by the sub-band coding method, such as a video file including a 5.1-channel audio bitstream, is input into the apparatus of FIG. 1, the dequantizing unit 10 restores sub-band PCM samples for each channel by dequantizing a quantized multi-channel audi