Abdoul-

Is there a study comparing the performance (quality and cpu/ram consumption) of codecs transcoding between rtpengine and asterisk/freeswith? Is rtpengine more efficient?

Can you specify which codec and number of concurrent channels (capacity) ? For older non-complex codecs (G726, GSM, etc) capacity won't make a difference, for not-as-old codecs (G729, iLBC, AMR-NB) it will make some difference, and for more recent complex codecs (AMR-WB, Opus, EVS) it will be significant issue. Also, rtpengine is using ffmpeg for codecs; freeswitch and asterisk run codecs included in their core source (also they have ways for other resources on the network to run codecs).

-Jeff