| 摘要 |
PROBLEM TO BE SOLVED: To shorten the processing time needed for calculating the mask value by producing previously an exponent conversion table in a significant digit unit of a significant digit of decibel calculation about the decimal value and extracting a decimal part from the decibel value to be converted to retrieve the exponent conversion table. SOLUTION: An exponent conversion table production means is prepared together with an exponent conversion table retrieval means. The exponent conversion table production means produces previously an exponent conversion table in a significant digit unit of a significant digit of decibel calculation about the decimal value of at least 1 or less. The exponent conversion table retrieval means extracts a decimal part from the decibel value to be converted and retrieves the exponent conversion table. For instance, this signal compression device consists of a digital audio input terminal 1, a sub-band encoding part 2, an FFT calculation part 3, a mask value calculation part 4, a bit allocation calculation part 5, a data quantization part 6, a transmission format forming part 7 and a compressed data output terminal 8.
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