| 摘要 |
<p>PROBLEM TO BE SOLVED: To provide an audio signal compression circuit with a more enhanced compression ratio than that of a conventional circuit and to provide an expansion circuit that restores the compressed signal to the original signal. SOLUTION: Filter banks 24L, 24R divide respectively received digital audio signals into 32 sub-band signals with an equal bandwidth. A sbutractor 26 subtracts a low frequency sub-band signal corresponding to the filter bank 24R from each low frequency sub-band signal of the filter bank 24L. Furthermore, an adder 25 sums each high frequency sub-band signal of the filter bank 24L and a high frequency sub-band signal corresponding to the filter bank 24R. A quantization circuit 31 quantizes and outputs a received signal. A bit stream generating circuit 32 generates a bit stream from the output of a quantization circuit 31 and provides the output of it. An expansion circuit 22 restores bit stream data outputted from a compression circuit 21 into original PCM audio data.</p> |
