| 摘要 |
PURPOSE:To obtain an excellent transmission characteristic by employing a polarity estimating unit having a frequency characteristic in a narrow band, which shows an excellent characteristic for a sound signal and a polarity estimating unit having an excellent characteristic which shows that characteristic for a MODEM signal of 9600 bps and identifying whether an input signal is a prescribed MODEM signal or not from the estimated values. CONSTITUTION:An estimation signal 8 is subtracted from the input signal 7 to attain a residual signal 9, which is inputted and quantized in an applicable quantizer 1. The quantized signal 10 is transmitted to a decoder. At that time a polarity estimating unit control part 6 controls the polarity estimating unit in response to the input signal 7. As for a MODEM signal of 9600 bps, the wide band fixed polarity estimating unit 5 is optimized with 'l=1 given. As for the sound signal other than the MODEM signal, the narrow band applicable polarity estimating unit 4 is operated with 'l=0 given, and estimates polarity so as to suit the input signal 7. In a decoder, an applicable reverse quantizer 2 quantizes the quantized signal 10 reservely, reproduces a residual signal 12, adds an estimation signal 13 to the signal 12 and outputs the added one as a reproduction signal 14.
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