In this case, Iam assuming you have verified the firewall on either side, and the network conditions are not an issue (eg. no packet loss, no crazy jitter and normal latency).
In some phones such as Grandstream or on your PBX, make sure you do NOT use the "adaptive jitter buffer" or similar settings. If possible disable that or change it to "fixed".
If you do, you may wonder why when you first start a call the user cannot hear you or the voice s........
espeak - is horrible and sounds very old and robotic
echo "hello there"|espeak
#don't know how to use
mbrola and plugins
cicero
jovie just seems to be a graphical interface to espeak
There is also sbreader/sapi
Google's Text To Speech Works Quite Well
#!/bin/bash
say() { local IFS=+;/usr/bin/mplayer -ao alsa -really-quiet -noconsolec........