G.726 & G.727 ITU-T compatible vocoders

Both G.726 & G.727 coders use an Adaptive Differential Pulse Code Modulation (ADPCM) system for coding and decoding samples. They quantize the difference between the speech (current) signal and a predicted speech signal. Prediction parameters are obtained by backward estimation from already quantized data. G.726 has individual optimized quantizers, where as G.727 has embedded quantizers that are specifically developed for packet network applications. The algorithm operates at 16, 24, 32, 40 and 64 Kbps. The overall compression ratio is 1.75:1, 2.8:1, 3.5:1, 4.67:1, or 7:1 for 14-bit linear data sampled at 8 kHz and 1:1, 1.6:1, 2:1, 2.67:1, or 4:1 for 8-bit companded data sampled at 8 kHz. The principal application of 24 and 16 kbps channels is for overload channels carrying voice in Digital Circuit Multiplication Equipment (DCME). The principal application of 40 kbps channels is to carry data modem signals in DCME, especially for modems operating at greater than 4800 kbps.


SoftRISC supports several processor platforms and maintains optimization efforts to improve performance specifications.