| 摘要 |
PURPOSE:To decode a source sound faithfully by preventing an analog output from having large amplitude variation even when the value obtained by accumulating difference values exceeds the output range of a DA converter 8 when ADPCM codes are decoded. CONSTITUTION:The ADPCM code data in an L register 1 and the difference values of a difference value data table ROM 5 selected with the quantization width pointer of an A register 4 are accumulated by an (n+1)-bit adder subtracter 6. When the output of the adder subtracter 6 exceeds a range of (n) bits, the most significant digit bit signal Sn+1 of an (n+1)-bit S register 9 which latches the accumulated value of the difference values becomes 1 and the output of an AND gate is fixed to 0 regardless of the value of an X-register latch signal Sx; and the low-order (n)-bit data of the S register 9 are not transferred to an X register 7, and the last value is held and outputted by the (n)-bit DA converter 8. |
