Digital audio decoder

Abstract

A digital audio decoder decodes or expands compressed data such as bit stream data, which are compressed based on the MPEG/Audio standard. Inverse quantization circuits perform inverse quantization on plural bit stream data, which are supplied thereto in connection with multiple channels respectively, thus producing inversely quantized data with respect to a prescribed number (e.g., thirty two) of sub-band samples respectively. The inversely quantized data are combined together among the multiple channels with respect to the prescribed number of the sub-band samples respectively. Then, a filter bank synthesizes together combined data corresponding to all of the sub-band samples, thus reproducing original digital audio signals. Multipliers are provided for use in gain control on the inversely quantized data with respect to the sub-band samples respectively. In addition, it is possible to additionally provide multipliers for amplifying the inversely quantized data of selected sub-band samples corresponding to low-frequency components of sound. This enables bass boost operations to be performed within the decoder. Surround effect processing circuits can be incorporated subsequently to the inverse quantization circuits, so desired surround effects are imparted to the inversely quantized data with respect to the sub-band samples respectively. The surround effect processing circuits simply contain multipliers whose coefficients are adequately controlled to achieve selective application of the surround effects among multiple channels.