12.6. Troubleshooting

I try to call someone, but fail to establish a connection.

There are several reasons why a call could fail:

Your connection to the Internet is broken.

Because Liphone uses the Internet to relay your calls, make sure that your computer is properly connected to and configured for the Internet. This can easily be tested by trying to view a Web page using your browser. If the Internet connection works, the other party might not be reachable.

The person you are calling is not reachable.

If the other party refused your call, you would not be connected. If Linphone is not running on the other party's machine while you are calling, you will not be connected. If the other party's Internet connection is broken, you cannot make the connection.

My call seems to connect, but I cannot hear anything.

First, make sure that your sound device is properly configured. Do this by launching any other application using sound output, such as a media player. Make sure that Linphone has sufficient permissions to open this device. Close all other programs using the sound device to avoid resource conflicts.

If the above checks were successful, but you still fail to hear anything, raise the recording and playback levels under the Sound tab.

The voice output on both ends sounds strangely clipped.

Try to adjust the jitter buffer using RTP properties in Preferences+Network to compensate for delayed voice packages. When doing this, be aware that it increases the latency.

DTMF does not work.

You tried to check your voice mail using the DTMF pad, but the connection could not be established. There are three different protocols used for the transmission of DTMF data, but only two of these are supported by Linphone (SIP INFO and RTP rfc2833). Check with your provider whether it supports one of these. The default protocol used by Linphone is rfc2833, but if that fails you can set the protocol to SIP INFO in Preferences+Network+Other. If it does not work with either of them, DTMF transmission cannot be done using Linphone.