I would like to discuss about calculating number of channels supported by an audio codec.
Generally I use to calculate using,
Number_Of_Channels = (CPUfrequencyInMHz * Ncores) / CodecSpeedInMHz
Let's take an example of G.723.1 encoding, rate 6.3 kbps and VAD disabled ran at about 10MHz.
CPU Frequency of My machine is 2Ghz=2000 MHz, Dual core Machine.
So on my machine, Number_Of_Channels =(2000*2)/10 =400 channel.
(I have not considered any overhead in case of transport and packaging data)