Opal is a full-featured library that supports a variety of protocols and multi-media fornats. Features include:

* Low latency RTP stack designed specifically for real-time multimedia
* Full featured H.323, SIP and IAX2 protocol stacks
* Audio codecs including G.711, GSM06.10, Speex and iLBC.
* Video codecs including H.261 and H.263
* Run-time loadable codec interface for proprietary or codecs such as G.729, H.263, H.264 and MPEG4
* Completely Open Source using the commercially friendly MPL 1.1 license

Through the use of a platform isolation library called PTLIB, Opal can run on tiny embedded systems or multi-processor servers.