An I-phone system design and implementation with a portable speech coding coprocessor
This paper presents a high quality, low bit rate, and portable Internet-phone system. The system consists of a mixed implementation of software and hardware. The hardware includes a portable box that can be plugged into the conventional parallel port. Three major parts are considered in this box: the speech compression unit, the host interface, and the speakerphone module. A low-cost non-delicate speech coprocessor is embedded to process the heavy job of speech coding, a CPLD device is employed to control the host access timing, a 16-bit PCM codec and an audio amplifier with acoustic echo cancellation features are introduced to optimize the speakerphone module. The experimental coding rate is 8.5 kbps. At such a rate, the popular modems can conform to offer full-duplex speech in real time. Modern applications of this system include digital simultaneous voice data (DSVD) transmission, such as net-game's talking and video-conferencing.