OPAL
Call control, signalling, RTP media, and codec plugins. Applications link this library and build it against PTLib.
https://github.com/OpalVoip/opalOpalVoIP
Open Phone Abstraction Library
Open source C++ for voice, video, and real-time communication. OPAL presents SIP, H.323, and the media that travels with them as one call model. PTLib is the portable library it is built on.
Repositories
Both libraries are in the OpalVoip organisation on GitHub. Clone PTLib first, then OPAL.
PTLib
Portable Tools Library. Threading, networking, and I/O for Unix, macOS, and Windows. OPAL requires a PTLib build.
https://github.com/OpalVoip/ptlibWhat the libraries cover
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Signalling
SIP and H.323, including the supplementary services and NAT extensions that sit with H.323, plus SDP for session description.
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Media
RTP and RTCP, audio and video codec plugins, mixing, and secure media when the build has SRTP.
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Platforms
Windows through the Visual Studio projects. Linux, macOS, and other Unix systems through the makefiles in each tree.
Get the source
Build PTLib, then build OPAL against that PTLib. Each repository carries the build instructions for its tree.
git clone https://github.com/OpalVoip/ptlib.git
git clone https://github.com/OpalVoip/opal.gitThe library license is the Mozilla Public License 1.0: OPAL and PTLib. Changes to the libraries are shared under that license. An application that links them keeps its own license.