One-way audio or not audio at all

• /etc/init.d/iptables stop

Device is SIP

• rtp debug, watch to see whether or not audio is coming/leaving
• Make sure sip.conf is correctly configured if Asterisk is behind NAT
• Make sure you are using correct codecs (same codecs in all the path of the call). Some devices does not support some codecs. Make tests using 1 same codec across the call path. Disable all others.
• Make sure NAT settings are correct (nat=yes) (in provider/device settings)
• Make sure you are using the same RTP range as your provider
• Make canreinvite = no in device settings
• Remove T.38 Support from device settings

• In /etc/asterisk/sip.conf find lines:

t38pt_udptl = yes
t38pt_rtp=no
t38pt_tcp=no

and change to:

;t38pt_udptl = yes
;t38pt_rtp=no
;t38pt_tcp=no

Reload Asterisk.

Device is H323

• If while connecting with an H.323 client, you get no audio or garbled audio and messages like this on the Asterisk console: rtp.c:489 ast_rtp_read: Unknown RTP codec 107 received, try to disable Speex or some other codec on Asterisk and/or the client side.
• If there is no audio in H323 calls, make sure in /etc/asterisk/h323.conf that you have binaddr set to your server's real IP address.
  • 
  • After this, restart Asterisk.

See also

• One-way audio problems