# OPAL - Open Phone Abstraction Library

### Version 3.12.3

## Open Phone Abstraction Library

This is a Open Source class library for the development of applications that wish to use the SIP and H.323 protocols for multi-media communications over packet based networks.

Copyright (C) 1999-2003 Equivalence Pty Ltd, All right reserved.
Portions Copyright (C) 2004 Post Increment, All rights reserved.
Portions Copyright (C) 2009 Vox Lucida Pty. Ltd., All rights reserved.

The documentation has been separated out into smaller pages, which can be accessed through the "Related Pages" link at the top of every web page, or here. The currently available pages are:

- Opal Classes lists the classes available to the application.

- A simplified API is available via the opal.h file.

- Connection handling in the OPAL library describes the working of the OpalConnection class, and the different stages used in call setup/teardown.

- IAX2 section of the OPAL library provides information on the working of the IAX2 component of this library.

- Terms used in the inline documentation attempts to give a non circular description of the terms used in this documentation.

- Opal architecture, from a H.323 perspective contains a somewhat dated description of the Opal architecture (from a H.323 perspective). It has been included to give a slightly different perspective, that may aid the reader.

- Media streams in the OPAL library attempts to give a description of the OpalMediaStream class.

### History

- 28 February 2005 - Converted from Doc++ to Doxygen format by Derek Smithies
- 10 May 2005 - Added some comments to explain data flow in a RTP classes
- 12 May 2005 - Changed main page to list only the Opal classes.
- 11 March 2006 - Add link to description of the IAX2 code.
- 20 March 2008 - Add documentation on the different phases of a call, which are driven by the OpalConnection class.
- 12 August 2010 - Add a description of the OpalMediaStream class.