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本文基于Z-80微处理机设计并实现了一种适于语音子频带编码(SBC)的自适应差值脉码调制(ADPCM)编码器,在发送端,编码器把并行输入的16比特二进制数字信号压缩为3比特或4比特码字;在接收端,解码器将其恢复为原来的16比特,选择了最佳参数,3比特与4比特数编码分别能获得25和33分贝的信噪比,用不超过二十片集成电路实现的硬件编码器,以 Z-80A CPU作为算逻单元(4兆赫主频),对每一样值的处理时间小于3200个时钟周期,可接受的输入采样频率高于1200赫兹,能够用于语音(8000赫兹采样)八子频带实时编码,增加外部硬件乘法器可以大大提高编码器的处理速度,使可接受的输入采样频率大于4000赫兹,因此能够用于语音两子频带实时编码,文中对这种编码器的基本算法,阶步参数、计算机仿算和硬件实现进行了详细讨论。
In this paper, an adaptive differential pulse code modulation (ADPCM) encoder suitable for speech sub-band coding (SBC) is designed and implemented based on the Z-80 microprocessor. At the sending end, the encoder converts parallel input 16-bit binary The digital signal is compressed into a 3-bit or 4-bit codeword; at the receiving end, the decoder restores it to the original 16 bits, selects the best parameters, and the 3-bit and 4-bit codes yield 25 and 33 dB respectively Noise Ratio, Hardware Encoder with Up to 20 Integrated Circuits, Z-80A CPU as Logic Unit (4 MHz Clock), Less Than 3200 Clocks Per Sample, Acceptable Input The sampling frequency is higher than 1200 Hz and can be used for real-time coding of eight sub-bands of speech (8000 Hertz sampling). Adding an external hardware multiplier can greatly increase the processing speed of the encoder so that the acceptable input sampling frequency is greater than 4000 Hz, Speech two sub-band real-time encoding, this paper discusses the basic algorithm of this encoder, step parameters, computer simulation and hardware implementation are discussed in detail.