| 摘要 |
In an encoder comprising a pulse producing unit for producing an excitation pulse sequence in response to a speech signal having electric power level, a detecting unit detects the electric power level in response to the speech signal and produces a detection signal. Responsive to the excitation pulse sequence and the detection signal, a processing unit processes the excitation pulse sequence in accordance with the detection signal and produces a processed signal. Preferably, the processing unit should comprise a classifying unit for classifying the detection signal into a plurality of classes in accordance with the electric power level, an extractor for extracting a plurality of excitation pulses in accordance with the classes to produce extracted excitation pulses, and a quantizing unit for quantizing amplitudes and locations of the extracted excitation pulses into quantized amplitudes and quantized locations. The quantized amplitudes and locations are represented by bits of a first and a second bit number, respectively, which numbers should be determined with a product of the number of the extracted excitation pulses and a sum of the first and the second bit numbers kept at a predetermined number. Alternatively, the detecting unit may detect the electric power level in response to the excitation pulse sequence.
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