| 摘要 |
PROBLEM TO BE SOLVED: To decode the digital speech signal of plural different formats by suppressing the increase of the capacity of internal RAM and of an operation clock frequency. SOLUTION: Two digital signal processors(DSP) 8 and 3 are used and each of them shares the load of audio decoding processing. DSP 8 decode-processes an audio BS(bit stream) from an input terminal 1 by a frame unit and generates frequency coefficient data to write into an external memory 11. DSP 3 reads frequency efficient data of this frame unit and decode-processes it to be PCM (pulse encoding) sample data. This PCM sample data is supplied for a D/A converter 6 through a PCM output I/F circuit 5 and converted to an analog speech signal. In a case when DSP 8 cannot decode-process one frame of audio BS in one frame period because of overloading, a deadline control circuit 12 makes DSP 8 to process the remainder in the next period and makes DSP 3 interpolate-operate in this frame period.
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