Linphone 3.4

Linphone is an internet phone or Voice Over IP phone (VoIP).
With Linphone you can communicate freely with people over the internet, with voice, video, and text instant messaging.
Linphone makes use of the SIP protocol , an open standard for internet telephony. You can use Linphone with any SIP VoIP operator, including the free SIP audio/video service.

Main Features :

- SIP user agent compliant with RFC3261
- Supports multiple calls simultaneously with call management features: hold on with music, resume, transfer...
- Audio with the following codecs: speex (narrow band and wideband), G711 (ulaw,alaw), GSM. Through additionals plugins, it also supports AMR and iLBC.
- Video with codecs: H263, H263-1998, MPEG4, theora and H264 (thanks to a plugin based on x264), with resolutions from QCIF(176x144) to SVGA(800x600) provided that network bandwidth and cpu power are sufficient.
- Supports IPv6
- Supports any webcam with a V4L or V4L2 driver under linux and Directshow driver on windows
- Text instant messaging and presence (using the SIMPLE standard)
- Addressbook
- DTMF (telephone tones) support using SIP INFO or RFC2833
- Understands SIP ENUMS (sip phone numbers using the naptr DNS service, without proxy)
- Acoustic echo cancelation using the great echo canceller available in libspeexdsp (works not only with speex codec of course)
- Multiple SIP proxy support: registrar, proxies, outbound proxies
- Digest authentication
- Nat friendly: guesses NAT address for SIP messages, uses STUN for RTP streams
- Efficient bandwidth management: the bandwidth limitations are signaled using SDP (b=AS...), resulting in audio and video session established with bitrates that fits the user's network capabilities.
- Can use plugins: to add new codecs, or new core functionalities, such as remote directory search of sip addresses for example.