A codec control method and its mounting technique for low bit-rate voice communication systems

A codec control method for low bit-rate multi-channel communication systems has been developed. By controlling multiple-channel codecs to output encoded voice packets with constant intervals, we reduced the packet-assembly delay and the delay variation. Based on this method, we also developed a channel assignment scheme when the number of channels in use is less than the number available. Moreover, in order to reduce the board size, we developed a high-density mounting technique, which can integrate 32 codecs and 32 echo-cancelers in half the area of a PCI expansion board. We applied these techniques to a prototype low bit-rate voice-over-ATM communication system, and confirmed that the cell-loss rate was reduced to 1/10, so 8% more channels are available than without using the control method (at 256-kbps transfer bandwidth)