Adaptive differential pulse code modulation/demodulation system and method

An adaptive differential pulse-code modulation-demodulation (ADPCM) method, comprising steps of:

• modulating an analog audio input signal into a data packet comprising a plurality of ADPCM digital data, an initial value and a scale factor;
• transmitting the data packet to a communication network;
• and
• demodulating the data packet coming from the communication network and reconstructing an analog audio output signal according to the ADPCM digital data, the initial value and the scale factor of the data packet,
• wherein the modulating the analog audio input signal into the data packet comprises:
• sampling, by a quantizer, the analog audio input signal with a fixed sampling frequency into a plurality of uncompressed digital sampled values;
• generating, by a differential calculation unit coupled to the quantizer, a plurality of digital differences by respectively subtracting the initial value from the plurality of digital sampled values;
• estimating, by a scale factor generator coupled to the differential calculation unit, the scale factor associated with the data packet according to a difference between the initial value and a greatest sampled value of the digital sampled values within a predetermined period;
• modulating, by a modulator coupled to the differential calculation unit, the plurality of digital values into the ADPCM digital data;
• and
• packing, by a packet generator coupled to the modulator and the scale factor generator, the ADPCM digital data within the predetermined period, the initial value and the scale factor into the data packet.

An adaptive differential pulse-code modulation-demodulation (ADPCM) system, comprising:

• a modulation module, coupled to a communication network, for modulating an analog audio input signal into a data packet to be transmitted to the communication network, wherein the data packet comprises a plurality of ADPCM digital data, and an initial value and a scale factor associated with the ADPCM digital data;
• and
• a demodulation module, coupled to the communication network, for receiving the data packet and demodulating the ADPCM digital data of the data packet according to the initial value and the scale factor to reconstruct an analog audio output signal, the demodulation module comprising:
• a receiver, for receiving the data packet;
• a packet parser, coupled to the receiver, for parsing the ADPCM digital data, the initial value and the scale factor of the data packet;
• a demodulator, coupled to the packet parser, for retrieving the ADPCM digital data parsed by the packet parser;
• a scale factor adjuster, coupled to the packet parser, for retrieving the initial value and the scale factor parsed by the packet parser;
• a differential calculation unit, coupled to the modulator and the scale factor adjuster, for generating a plurality of compressed digital sampled values according to the ADPCM digital data, the initial value and the scale factor;
• and
• a de-quantizer, coupled to the differential calculation unit, for de-quantizing the compressed digital sampled values to reconstruct the analog audio output signal.