And if you're willing to accept poorer video quality, these DVCs can be throttled back to 128 Kbps.
Audio quality is a separate issue.
Gargly, broken up or delayed sound can become a real problem if there are too many bridges or routers introducing variable latency between the end points. The interaction between connected H.323 and H.320 videoconferencing systems is complicated. Video performance is strongly affected by the nature and speed of the processors at each end, but also by the choices of audio compression algorithms in use. Video performance, measured by delivered frame rates, depends most strongly on the power and efficiency of the encoding processor. Add the MMX instruction set, and the output should increase to about 10 fps.