Features

• audio with the following codecs: speex (narrow band and wideband), G711 (ulaw,alaw), GSM, and iLBC (through an optional plugin)
• video with H263-1998, MPEG4 and theora codecs.
• Supports any webcam with V4L or V4L2 driver under linux
• Any webcam on windows
• text instant messaging and presence (using the SIMPLE standart)
• Addressbook
• DTMF (telephone tones) support using SIP INFO or RFC2833
• understands SIP ENUMS (sip phone numbers using the naptr DNS service, without proxy)
• echo cancelation using the great speex echo canceler
• SIP proxy support: registrar, proxies, with digest authentication
• STUN support for traversal of UDP NATs (=firewall)
• sound backend using either ALSA (the most efficient), OSS, or arts (kde sound daemon)
• supports IPv6
• 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.

On linux, linphone can be used as a small GNOME/GTK+ application or as a console mode application (the executable is called 'linphonec'). The existence of this console mode application gives the possibility to run VoIP calls from scripts, or to run linphonec as a small auto-answering phone.

On windows, it is available as graphical application.

Linphone is known to work under Linux, Windows, FreeBSD, OpenBSD.
The console version (linphonec) run on arm-linux. Instructions for arm cross-compilation are given in the README.arm file within linphone's source.
Additionaly it has been reported to work on several embedded chips: search google or the mailing lists for more details.

Here is the non-exhaustive list of standarts linphone is using;

• SIP (Session Initiation Protocol, rfc3261), the signaling protocol
• RTP (Realtime Transport Protocol, rfc3550), the real time streaming protocol
• RTP Payload for DTMF Digits, Telephony Tones and Telephony Signals
• STUN (Simple Traversal of UDP NATs)
• RFC4629 (Usage of video H263 over RTP)
• RTP payload format for theora encoded video
• RFC 3016 - RTP Payload Format for MPEG-4 Audio/Visual Streams