The previous version of the FAQ (which includes information on OpenH323) can be found at http://www.voxgratia.org/docs/faq.html, but this is no longer being updated.

1.2 - My question is not answered by the FAQ, how can I ask a question?

Send any suggestions by email to the appropriate Opal mailing list. See the Wiki page for more information.

1.3 - Who maintains the FAQ?

This FAQ is maintained by Craig Southeren of Post Increment who can be reached by email at craigs@postincrement.com

1.4 - Who owns and runs the OPAL mailing lists and OpalVoip web site, and how do I contact them if I am having problems?

The Opal mailing lists is hosted by SourceForge and maintained by the OpalVoip project managers. See the developer list for contact details.

See 2.1 and 2.3 for information on subscribing to any OpalVoip list.

The OpalVoip web site is maintained by craigs@postincrement.com | Craig Southeren.

The openh323.org web site is not maintained by anybody. Please don't email us about it.

1.5 - The FAQ describes something that sounds like my problem, and it refers to a document that I don't really understand. I don't have time for all of this - can I just email someone or contact them via IM and get them to explain it all to me?

If you feel the urge to contact the core developers, then understand that you are asking them to give up their time and spend it on your problem. If you can't be bothered spending the time, then why should they?

So before doing emailing or contacting via IM, make sure you do the following:

Make sure you have read this FAQ, and any associated documentation, thoroughly,
Search the mailing list, or use Google, to find any posts or documents regarding your problem
If you don't understand the existing documentation at all, then you probably won't understand the answer. Consider spending more time trying to understand the problem
Ask specific questions, not general ones
Accept that the person you contact may be busy, or in another time zone, and cannot answer your question
Be polite

1.6 - Not used

1.7 - Not used

1.8 - What is OPAL?

See 10.1

1.9 - What are the development plans for OPAL?

The latest development plans and milestones can be found here

1.10 - How do I get write access to the OPAL Subversion repository?

Through experience, the project team has tended to limit write access to developers who have demonstrated a working knowledge of the OPAL and PTLib code by providing good quality code patches over a period of at least six months.

Write access is also occasionally granted to non-developers who have a specific need, such as documentation or release management, or who are sponsored by another senior OPAL developer.

1.11 - What is the status of the OpenMCU program?

OpenMCU was originally created in May 2000 by Craig Southeren as an experiment to investigate some ideas about how an audio MCU might work. It has grown from there.

Over the next two years the code was modified by Derek Smithies and Roger Hardiman to include video capabilities and to add extra functions such as support for multiple rooms. The final result of this effort was OpenMCU v1.7.1 which supported both video and audio, but was unstable and difficult to understand. Guilhem Tardy has also released some notes on how to add H.263 support to OpenMCU at http://www.salyens.com/ffcodec/

OpenMCU version 2 was started in March 2004 with support from Citron Networks with intent of fixing the known problems with version 1. The code was almost completely rewritten to be more modular, and the stability issues were addressed. This work ended around August 2004 with a version that only supported audio.

In March 2006, with the support of Stonevoice, a full-featured version of OpenMCU that supports video and audio was released.

An version of OpenMCU is in developement that supports OPAL through use of the Woomera protocol

1.12 - What is the license used for PTLib and OPAL, and why wasn't the GPL used?

PTLib and OPAL are available under v1.0 of the Mozilla Public License (MPL). The MPL was chosen specifically because it permits commercial software to be combined with OPAL in ways that the GPL does not, but still requires changes to the released code to be contributed back to the community. The exact text of the license used for OPAL can be viewed in the Subversion repository

A more detailed description of the reasons why the MPL was chosen can be found in my keynote speech ? that was presented at the Free Software/Open Source Telephony Summit held by the German Unix User Group in Geilenkirchen, Germany in January 2005

1.13 - What restrictions are placed on the software can I combine with PTLib and OPAL?

The MPL places no restrictions on what software you may combine with PTLib or OPAL. You can use Opal with closed source software or with Open Source software released under other licenses, provided that the other license allows this.

1.14 - What license restrictions are placed on changes I make to PTLib and OPAL?

Paragraph 3.2 of the MPL license states:

"Any Modification which You
create or to which You contribute must be made available in Source Code form
under the terms of this License..."

For the purposes of the MPL, "Modification" is defined as:

"...addition to or deletion from the substance or
structure of either the Original Code or any previous Modifications. When
Covered Code is released as a series of files, a Modification is:

A. Any addition to or deletion from the contents of
a file containing Original Code or previous Modifications.

B. Any new file that contains any part of the
Original Code or previous Modifications."

In plain language, this means that any changes you make to any existing Opal source file must be released under the same MPL license. This same applies to any new file that contains part of any previously released code.

However, the MPL places no restrictions on any new files you create that contain wholly original code. You can choose to release (or not release) these files under any license you choose. Please note that files not compatible with the MPL license will not be included in the official Opal Subversion repository

1.15 - Where did PTLib and OPAL come from, and who is responsible for it now?

PTLib was originally called PWLib, and was created in 1992 by Robert Jongbloed and Craig Southeren. The copyright for the code was transferred to an Australian company called Equivalence Pty Ltd in 1996. Work commenced on OpenH323 in 1998, and PWLib and OpenH323 was released as Open Source software using the MPL license in the same year. The openh323.org domain name was acquired at this time, and the code was made available via a private server at that web address. OPAL coding started in late 1999 and was released under the same license.

In early 2000, Robert and Craig sold Equivalence Pty Ltd and the rights to the openh323.org domain name to a US company called Quicknet Technologies Inc. They were also employed by Quicknet to support OpenH323 and to develop associated software. The OpenH323 CVS and mailing list was moved to a new server managed by Quicknet.

The OpenH323 CVS was moved to SourceForge in May 2003. Robert and Craig ceased employment with Quicknet in June 2003.

In October 2007, PWLib was renamed to PTLib. The OPAL and PTLib repositories were then migrated to Subversion, and the project was moved to the opalvoip project on SourceForge. OpenH323 was renamed h323plus and was moved to the h323plus project on SourceForge

The project continues to grow and mature thanks to the work of a dedicated group of developers. The following people have accepted the responsibility of CVS write access as well as the ability to close patch submissions, and can be considered to be the people responsible for leading OpenH323, OPAL and PTLib:

Craig Southeren, Damien Sandras

The following developers have CVS write access and are active contributors to the project

Derek J Smithies, Simon Horne, Robert Jongbloed,

The following developers have CVS write access and contribute occasionally:

Shawn Hsiao, Vyacheslav Frolov, Yuri Kiryanov,
Kilian Krause, Roger Hardiman, Hannes Friederich

There are many more people (far too many to list) who have contributed time and code to the project. Please accept my thanks, and my apologies that you cannot be listed here.

2. USING THE OPAL MAILING LIST

2.1 - How do I subscribe to a mailing list?

The only way to subscribe is via the SourceForge mailing list page

2.2 - How do I unsubscribe from the mailing list?

The only way to unsubscribe is via the SourceForge mailing list page

2.3 - How do I make a posting to the mailing list?

Send an email to the appropriate email address:

opalvoip-user@lists.sourceforge.net
opalvoip-devel@lists.sourceforge.net

2.4 - What are the mailing lists used for?

This list is used for asking any questions related to the Opal project or related technologies.

2.5 - What is the mailing list not used for?

This list is not used for:

SPAM
Questions unrelated to Opal
Selling your company's services or products
Finding someone to do your homework/final year project/doctorate

2.6 - There is too much traffic on the mailing list. Is there a digest?

Yes.

When you subscribe to the list, make sure you select "Yes" on the option labelled "Would you like to receive list mail batched in a daily digest?". If you are replying to messages contained in a digest, please make sure you change the subject line to reflect your question rather than retaining the arbitrary digest title.

2.7 - Is there an searchable archive of the list available?

Yes.

See the Archives links on the SourceForge mailing list page

2.8 - Are there any rules?

No flaming. No trolls. Be nice. Be warned.

2.9 - Who enforces the rules?

There are several enforcers who ensure that the rules are applied fairly and consistently. If you are emailed by one of them for being off-topic, for flaming, or if they indicate that an email thread is closed, it is suggested that you listen carefully unless you have kneecaps you no longer care about.

2.10 - How can I ensure someone will answer my question?

There is absolutely no guarantee that someone will answer your question. If you want to maximise the chances of an answer, do the following:

be polite
provide enough information to allow the problem to be duplicated by someone else
describe what you have already done to fix the problem
don't bother saying you need a reply urgently

An excellent essay on how to ask questions be found at http://www.catb.org/~esr/faqs/smart-questions.html. Another excellent essay on how to report bugs can be found at http://www.chiark.greenend.org.uk/~sgtatham/bugs.html

2.11 - But I really need an URGENT answer to my question?

Then offer money. Lots of money. But don't bother posting your request multiple times unless you don't mind annoying lots of people as well as looking like a complete loser.

There is one class of posters who appear regularly asking for urgent help, and these are students asking for help in completing their final year project. Writing a VoIP application seems to be a popular topic for final year university students, and I'm sure that most of them actually do the work themselves. The excellent Ekiga (http://www.ekiga.org - formerly GnomeMeeting) application started in exactly this way.

As always, though, there are students who seem to think that they can leave everything to last minute and then just grab some Open Source project and fill in the missing bits. When this does not work, they post plaintive cries on the list asking if someone has created what they need. Strangely, they seem to think this is a perfectly reasonable request so when they don't get an answer, they keep asking. Amazing....

What they should do (apart from starting their project earlier so they have plenty of time to finish) is start working on the code themselves, using one of the sample programs as basis. When they encounter a problem, they should ask specific questions that can be answered by someone who has the time to do so. Asking someone else to provide the entire project working exactly to their specifications is just unreasonable - so please don't waste everyone's time by asking.

2.12 - Who answers questions on the list?

Anyone may answer questions, but the most interesting ones will normally be answered by one of the principal developers who include Robert Jongbloed, Derek Smithies, Roger Hardiman, Damien Sandras or Craig Southeren. If you receive a reply from any of these people, then listen carefully because they are very likely correct.

2.13 - I want to help by answering questions? How do I do this?

If you see a question for which you know the answer, or you see a reply that you know to be incorrect, then please join in the discussion. And be gracious if you make a mistake - being wrong is not a crime but being impolite certainly is.

2.14 - Not used

2.15 - Not used

2.16 - Can I ask questions about how to use/debug/understand another H.323/SIP/IAX stack?

The Opal mailing lists are intended for questions and issues related to the Opal stack. If you have questions about a commercial stack, then you should contact the stack vendor for support. Commercial stacks are usually covered by non-disclosure agreements, so it's unlikely that anyone on the list could help you without breaking that agreement.

If you have questions regarding protocols that are not related to Opal or any other specific stack, then the Packetizer site (see http://www.packetizer.com has many excellent resources.

3. DOWNLOADING CODE

3.1 - Where can I download source code from?

The official source code archives (tarballs and ZIP files) are available from the downloads page of the OpalVoip SourceForge project, which can be found at http://sourceforge.net/project/showfiles.php?group_id=204472.

The Ekiga (http://www.ekiga.org - formerly GnomeMeeting) project also maintains source code tarballs (Linux only) at http://snapshots.seconix.com and http://snapshots.voxgratia.org. These are also created from the official CVS repository but use different scripts.

3.2 - Where can I download binaries from?

The Ekiga (http://www.ekiga.org - formerly GnomeMeeting) team maintain up to date binary packages of Opal and PTLib for Linux at http://www.gnomemeeting.org/index.php?rub=5&pos=0

The XMeeting Project team maintains up to date binary packages for MacOS X at http://sourceforge.net/projects/xmeeting/

3.3 - Where can I get the very latest source code from?

The latest source code is always in the Subversion repository (see 3.4 below), but the Ekiga team maintains very recent source code tarballs for Linux at http://snapshots.seconix.com and http://snapshots.voxgratia.org

Please read the Wiki for more information on downloading from the Subversion repository.

See 3.7 below on how to find a particular version of the source code in the CVS

3.4 - How do I access the Subversion repository?

The Subversion repository is hosted by SourceForge. See the Wiki for more detailed instructions. A web interface to the repository can be found here

See 3.7 below on how to find a particular version of the source code.

3.5 - Where can I get ZIP versions of the source archives

ZIP files are now created for all releases. We recommend WinZIP.

See section 4.2, 4.7 and 4.8 for related problems

3.6 - How do I know what version to download?

Normally, the recommended stable version is the most recent version available from the SourceForge download page.

3.7 - Where can I download a particular version of the code?

If the version you require is not available on any of the download sites (see 3.1 above) then you will have to extract it from the Subversion repository (see 3.4 above).

Every release of Opal or PTLIB is available as a Subversion tag or branch. For example, version 1.6.0 of PTLib is assigned the tag v1_6_0. This is useful for doing compares between versions.

3.8 - Why isn't the latest code and information on openh323.org, and why don't you do something about it?

Quicknet Technologies, Inc own the openh323.org domain name. I'm not associated with Quicknet, and I have no way of contacting them, or of making changes to the openh323.org web site

3.9 - What Phobos, Deimos and Centauri?

These names are all code names for various releases of OPAL.

For those who are interested, the first two OPAL releases are named after the two moons of Mars, which appropriately translate to Fear (Phobos) and Panic (Deimos). Future code names for OPAL will come from star names - the first one will be Centauri.

3.10 - Where can I download the old PWLib GUI code?

This code is no longer supported and is not available for download as a tar.gz file or ZIP file. It can be extracted from the OpenH323 CVS using the "pwlib_win32" module

3.11 - Why is the configure.in file is missing when I extract source code from the CVS?

The configure.in files in PTLib and Opal are named configure.ac .

4. COMPILING THE CODE

4.1 - The code does not compile - what is the problem?

Yes, the code does compile but something on your system is causing a problem. You need to find what that problem is.

Here are some quick tips:

Make sure that the ptlib directory is renamed to "ptlib" and the Opal directory is "opal" as the original tarball may have different names or your CVS client may have used the module name instead
You need Bison and Flex installed as well as a compiler and associated tools. We recommend gcc and Make for Unix platforms, and Microsoft VS.net 2005 for Windows although other environments are supported. Note that the bison and flex package provided as part of the Windows build instructions (see 4.5) must be installed in C:\TOOLS unless you seriously know what you are doing.
Check the ReadMe.txt files for more information

NOTE: Since there is no ReadMe.txt file in opal-v3_0_0-src.tar.gz available from sourceforge I dare to leave some comments here:

1) If you are trying to build opal lib under linux you should have /root/ptlib and /root/opal directories.

2) If you try to build ptlib-v2_0_0 with opal-v3_0_0 you may possibly use the following lines to succeed:

cd /root/ptlib

./configure --enable-v4l=no --enable-v4l2=no

make

cd /root/opal

./configure --disable-versioncheck

make opt

4.2 - Microsoft Visual Studio will not load the DSP and DSW files provided with Opal

You have downloaded the tar.gz source archive, and then used an archive program that does not correctly handle tar.gz files under Windows which has resulted in project files with incorrect end of file characters. MSVC cannot handle project files of this type, although it does handle source files in this mode.

To fix the problem, use a program like WinZIP that will do the correct conversion automatically, or use .ZIP version of the archives. You can also load the DSP and DSW files into a text editor and fix the end of line characters manually.

If you have this problem, you most likely will have the problems described in 4.7 and 4.8 as well.

4.3 - I know the OpenLDAP/OpenSSL/Foobah library on my system is broken, but OPAL uses it anyway. How do I prevent this?

Run "./configure" for PTLib or OPAL with the appropriate flag to disable the module you want to avoid. Use "./configure --help" for a list of these flags.

4.4 - How do I cross compile OPAL for another platform?

Set the following environment variables before running "./configure":

 export CXX=<toolchain directory>/g++ 
 export CC=<toolchain directory>/gcc

It may also be necessary to tweak LDFLAGS and CFLAGS using environment variables as well, or to disable certain features (see 4.3 above)

4.5 - Are there detailed instructions for building OPAL and PTLib on Windows?

Instructions for compiling OPAL and PTLib on Windows can be found at in the Wiki:

4.6 - Can I compile OPAL/PTLib using VS.NET 2003, VS.net 2005 and Visual C++ 2005 Express Edition?

Yes.

Use the ptlib.sln and opal.sln files for VS.NET 2003.

Use the ptlib_2005.sln and opal_2005.sln files for VS.net 2005.

4.7 - How do I fix the Windows build error "Cannot open include file: 'ptbuildopts.h': No such file or directory"?

The file ptbuildopts.h is created from ptbuildopts.h.in by the ptlib/configure.exe program. If this step does not occur, then ptbuildopts.h is not created and the build process will fail. You need to determine why this is happening. See section 4.2 above or section 4.25 for a possible explanations

4.8 - How do I fix the Windows build error "Configuring Build Options \ This program cannot run in DOS mode \ Error executing c:\windows\system32\cmd.exe"?

This indicates that the file ptlib/configure.exe program cannot be executed, probably because it is missing or corrupted. Download a new version and make sure it is a working Windows executable. See section 4.2 above for a possible explanation

4.9 - Not used

4.10 - How do I report a bug in the code?

The best way to report a bug is to use the Bug tracker at the OpalVoip Source Forge site.

If you have a patch that adds a new feature, then please use the patch tracker as described in 4.16

4.11 - Not used

4.12 - How do I fix errors about missing include files like "gsmcodec.h" or "lpc10codec.h"?

These files were removed when support for audio codec plugins was introduced. See the document http://www.voxgratia.org/docs/codec_plugins.html#converting for more information

4.13 - How do I fix errors like "Cannot open source file: getdate_tab.c': No such file or directory"?

You need to install the GNU bison and flex programs program. See http://www.voxgratia.org/docs/pwlib_windows.html#flexbison for information on how to do this.

4.14 - How do I compile OPAL on Solaris?

Instructions can be found at http://www.voxgratia.org/docs/solaris.html

4.15 - How do I make the code smaller?

First of all, make sure you are using the Release build ("make opt" for Unix) and the "No Trace" build for Windows.

If you do not need to create trace files, you can half the size of the Unix binaries by ensuring that OPAL is compiled with the PASN_NOPRINTON and PASN_LEANANDMEAN symbols defined, and that everything is compiled without the PTRACING symbol

Also make sure to turn off features that you do not need, such as video. This can be done changing defines in the include/opalbuildopts.h file.

It is possible to get a Windows executable that includes video and audio with PTLib and OPAL linked statically, and dynamic links to everything else, in an .EXE that is under 1Mbyte (provided tracing is disabled)

Linux executable is always larger that the comparable Windows program, but it possible to get the same code in under 3Mbytes.

4.16 - How do I submit patches to the code?

If you have a code patch that adds a new feature or capability, or fixes a bug, then please submit it using the SourceForge patch tracker at https://sourceforge.net/tracker/?group_id=204472&atid=989750.

You must make sure the patches are against a reasonably late version of the source. It is best to use SVN and do an "svn update" immediately before creating the patches, as if it is too old it will not apply properly. it also helps to tell us which branch you are on. Also do not send whole source files, they are even harder to deal with and SVN can produce diffs quite easily. The command "svn diff > my.patch" is all you need to do. Finally, please make sure they follow the coding standards!

Our time is at least as valuable as yours, more so really :-), and if it gets too hard for us to apply your patch, it won't happen, and that does OPAL and the Open Source movement no good at all. It will make your life harder as you have to reapply your changes every time you get bug fixes from the SVN. So do the right thing!

If you are reporting a bug without a code patch, then please use the bug tracker as described in 4.10

4.17 - How do I fix the following error on when compiling using MSVC 6 "WARNING: the following file requires upgrading: \ C:\Program Files\Microsoft Visual Studio\VC98\INCLUDE\XTREE \ Please run 'msvc6chk upgrade' to upgrade this file"?

There are several major defects in the STL header files shipped with MSVC 6. These defects are sufficient to crash programs (like PTLib) that rely on the correct behaviour of global static variables. Fortunately, the original authors of the STL libraries for MSVC have published new versions of the files necessary to correct the worst of these problems.

PTLib checks for the correct header file versions when a new compile is started, and will prevent the compile from continuing until the correct header files are installed. There is a "one-click" solution to this problem that will upgrade your files painlessly and quickly - see the following URL for more information: http://www.voxgratia.org/docs/pwlib_windows.html#msvc_headers or download the upgrade program from http://www.voxgratia.org/releases/msvc6chk.zip

4.18 - How do I stop my program from immediately crashing with a dialog saying "The application failed to initialise properly. Click on OK to terminate the application" when I use the DLL versions of PTLib and OPAL, even though the statically linked versions work OK?

This is probably because you have not upgraded your MSVC 6 header files - see 4.17 above

4.19 - How do I fix the following error on Windows when building PTLIB.DLL/OPAL.DLL "dllmain.obj : fatal error LNK1202: "c:\ptlib.msvc\lib\ptlib.pdb" is missing debugging information for referencing module"?

This error seems to be a result of the linker getting confused about the debugging information in the pdb file. The only solution is to delete the entire ptlib/lib or opal/lib directory and recompile everything again. You will have to exit MSVC before you can do this, as the environment keeps open files in that directory.

Note that doing a "clean" is not sufficient, and simply removing the .pdb file is not enough either - the entire directory must be removed.

4.20 - Not used

4.21 - Not used

4.22 - Not used

4.23 - How do I fix warnings about PVXMLSession and OpalVXMLSession not found compiling the opennivr/vxmltest/woomera programs?

The VXML code requires the header files for the expat XML parser to be installed on your system. If you are using Unix, then make sure you have the "expat-devel" package installed. If you are using Windows, then a recompiled version of expat and the required header files can be downloaded from http://www.voxgratia.org/bin/expat_lib.zip.

For more information on Jim Clark's excellent XML toolkit, see http://www.jclark.com/xml/expat.html or http://expat.sourceforge.net

4.24 - The Windows configure process for PTLib or OPAL is finding the wrong version of a library - how do I stop this?

The configure program for Windows will search all directories looking for installed versions of libraries such as expat.lib and openldap.lib. If other programs have versions of these libraries installed, then it is likely that configure will pick the wrong file. This is particularly likely if you have two development environments installed, such as VS.net and MSVC.

To fix this, it is necessary to tell configure not to search in certain directories for files. This can be done by changing the configure command line in the project file, but there are also several predefined environment variables which, if set, will be used by configure to determine which directories to ignore. These variables are set to a list of directories separated by semicolons (";") :

PWLIB_CONFIGURE_EXCLUDE_DIRS	ignore these directories always
MSVC_PWLIB_CONFIGURE_EXCLUDE_DIRS	ignore these directories when compiling using MSVC 6
VSNET_PWLIB_CONFIGURE_EXCLUDE_DIRS	ignore these directories when compiling using VS.net 2003

4.25 - I used to be able to compile PTLib without any problems, but now I get warnings like this "Please remove ptlib\include\ptlib\msos from the tool include path and from the pre-processor options for this project" - how do I fix this?

Prior to the Janus release of OPAL, it was necessary to include the "platform specific" include directory into the include paths for the environment. This requirement was removed because it was the source of many problems for users. The changes required to remove this dependency cause problems if the "platform specific" directory is retained, so the code has been altered to generate the above error if the include paths are not changed.

To remove the error, make sure that there are only three directories configured into the VS.net or MSVC 6 include path (as described at http://www.voxgratia.org/docs/pwlib_windows.html#dirs).

If you get this error while compiling a program, and you have verified that the environment includes paths are correct, then ensure that the Preprocessor options for the project do not contain the "platform specific" directory.

4.26 - How do I fix errors compiling asn_grammar.y/asn_grammar.cxx?

On some platforms, compiling the ASNParser results in errors like this:

 In file included from /ptlib/include/ptlib/contain.h:782,
 from /ptlib/include/ptlib.h:146,
 from asn_grammar.y:77:
 /ptlib/include/ptlib/contain.inl: In constructor PAbstractList::PAbstractList()':
 /ptlib/include/ptlib/contain.inl:428: warning: right-hand operand of comma has no effect
 asn_grammar: In function `int yyparse()':
 asn_grammar:5045: error: expected primary-expression before "__attribute__"
 asn_grammar:5045: error: expected `;' before "__attribute__"
 asn_grammar:5040: warning: label `yyerrlab1' defined but not used

These errors are probably due some flag differences in the bison pre-processor, but the solution is very simple. Simply upgrade your code to at least the last Janus release version (as of 1 Nov 2004, this was Janus patch 4) because that version (and all subsequent versions) no longer require the ASN parser to be compiled. See 4.21 for more information

4.27 - When I compile PTLib I get warnings like "../common/getdate.y: conflicts: 8 shift/reduce, 18 reduce/reduce" - is this normal?

Yes, this is normal and does not indicate that there is a problem. It can be safely ignored.

4.28 - When I compile PTLib I get a warning like "In static member function `static std::ostream& PTrace::End(std::ostream&)': warning: unused variable 'rb'" - is this normal?

This warning has been left in to remind us of a potential problem that we need to fix some day. For now, it can be safely ignored.

4.29 - How do I fix link errors about missing functions when compiling DLLs on Windows?

The short answer is that this problem is often a side-effect of the method used to maintain compatibility across various versions of the DLL libraries. The simplest way to solve this problem is to delete the files with the extension ".dtf" and then completely rebuild the DLLs. This should solve the problem.

Why does this work?

The long answer is that PTLib and OPAL attempt to preserve the ordinals used for DLL entry points across different versions of the libraries. To do this, the MergeSym program compares the function signatures in the DLLs to the entry points listed in the .dtf files, and makes sure that the final file ends up with compatible ordinals. The default .dtf files are created on a system with all optional features enabled, which means that if they are used on a system with less features, there are unresolved symbols left over.

4.30 - How do I link PTLib or OPAL applications statically in Windows?

To create a statically linked application in Windows, you simply need to link with the static versions of the libraries rather than the dynamic ones. A guide to the library names under Windows is show below. Note that you must not mix static and dynamic versions of the libraries in the same executable - this will cause very strange and hard to diagnose errors.

Library	Static Debug	Static Release	Dynamic Debug	Dynamic Release
ptlib	ptlibsd.lib & ptclibd.lib	ptlibs.lib & ptclibd.lib	ptlibd.lib & ptclib.lib ptlibd.dll	ptlib.lib & ptclib.lib ptlib.dll
openh323	openh323sd.lib	openh323d.lib	openh323d.lib openh323d.dll	openh323.lib openh323.dll
opal	opensd.lib	opals.lib	opald.lib opald.dll	opal.lib opal.dll

4.31 - How do I link PTLib or OPAL applications statically on Unix?

The standard makefiles allow static executables to be created using the following commands:

"make noshared" - creates a statically linked executable with debug information

"make optnoshared" - creates a statically linked executable without debug information

4.32 - How do I stop configure from finding the wrong header files on Windows?

The configure program on Windows will search all local hard drives looking for header files and libraries that indicate which compile time options can be enabled. Sometimes, configure will find files that it should not, usually because it is searching through the wrong directories. This can occur if packages such as Cygwin or MSys are installed on the host computer.

To prevent configure from attempting to use these header files, it is necessary to indicate which directories should be ignored during the scanning process. To tell configure to ignore a directory, you must add the path to be ignored to the PWLIB_CONFIGURE_EXCLUDE_DIRS environment variable.

In addition, the following environment specific environment variables can be used to customise the directories used for various compile environments. This is especially useful when multiple environments are installed on the same machine, (i.e. having both MSVC 6 and VS.net 2003 installed)

MSVC 6	MSVC_PWLIB_CONFIGURE_EXCLUDE_DIRS
VS.net 2003	VSNET_PWLIB_CONFIGURE_EXCLUDE_DIRS
VS.net 2005	VSNET2005_PWLIB_CONFIGURE_EXCLUDE_DIRS

Note that technique can also be used to reduce the time taken to perform the configure scan by not scanning large directory trees or even entire drives.

Note that versions of configure prior to version 1.5 (released on 26 June 2006) do not support ignoring entire drives.

You can also specify directories to ignore on the configure command line using the --exclude-dir command line option, or you can specify the names of additional environment variables that contain directories using the --exclude-env option. See the custom build information for the project specific header file to edit the command line to configure.

4.33 - How do fix errors about missing "MSVC80.DLL" or "MSVCR80.DLL" file when debugging OPAL programs using Visual C++ 2005 Express Edition?

This problem is caused by having dependent libraries, such as OpenSLL or Expat, that have incorrect references to the run-time library. To fix this problem, you will need to find correctly packaged versions of these libraries.

Some references to libraries that are known to work are provided below. Please email craigs@postincrement.com if you locate any other sites that provide working library packages

OpenSSL	Available for Shining Light Productions http://www.slproweb.com/products/Win32OpenSSL.html
Expat	Available from the SourceForge Expat project page http://sourceforge.net/project/showfiles.php?group_id=10127

4.34 - How do I fix gcc errors about "PAtomicInteger" when compiling OPAL?

This error is usually indicates the presence of two incompatible versions of the PTLib headers, and that the OPAL build process is detecting the wrong set which is probably located in /usr/local/include or /usr/include (check the configure output to be sure)

The easiest way to solve the problem is to set the PWLIBDIR environment to point to the correct version of PTLib. Alternatively, deinstall the incorrect version so that the auto-detection find the correct version.

4.35 - I cannot find the Console Components library files (ptclib.lib and ptclibd.lib) in recent builds of PTLib. Where are they?

The Console Components library (ptclib.lib/ptclibd.lib) was removed as a separate library in late July 2006, and all of the source files were added to the base Console library. This simplifies the management of libraries under Windows, and brings the code in line with the Unix library.

5. CODECS

5.1 - Why is there no G.723.1/G.729 codec in OPAL?

These codecs are covered by patents, and are not available as Open Source implementations.

5.2 - Can I use the ITU reference code for G.723.1 and G.729?

Use of these codecs and the reference implementations still requires licenses from the patent holders. See the relevant ITU specifications for more information.

The ITU reference code for G.723.1, G.729 and several other codecs can be obtained from the ITU web site at http://www.itu.int/publications/itu-t/list-t-soft.html

5.3 - Where can I get licensed G.723.1 and G.729 codec implementations?

There are several companies that sell implementations of these codecs for various platforms. Be prepared to pay more than $10k for each codec implementation, plus $10 per copy sold/used.

Some companies that are known to have licensed codec implementations available are:

VoiceAge (http://www.voiceage.com) - G.729 and G.723.1 for Windows and Linux
Intel (http://www.intel.com/software/products/ipp/) - A wide range of codecs

5.4 - Can I use the Microsoft ACM G.723.1 codec in my Windows program?

It is not clear whether this is legal or not, but there is reason to believe that usage of the MS G.723.1 codec by programs other than those authorised by Microsoft is in violation of the DMCA. We choose not to use this codec for that reason - you make your own choice.

Also, Vista and Windows 7 ACM no longer supports the G.723.1 format. http://en.wikipedia.org/wiki/Features_removed_from_Windows_Vista#Graphics.2C_DirectX_and_Video

5.5 - How do I use the H.263 video codec with NetMeeting?

TBD

5.6 - How do I add my own audio or video codec to Opal?

OPAL supports plugin codecs. See http://www.voxgratia.org/docs/codec_plugins.html for more information.

5.7 - What audio codecs are supported by OPAL?

G.711 uLaw and ALaw
GSM 06.10
Microsoft-GSM
LPC-10
Speex
iLBC
G.726
G.723.1 (Windows and Linux: requires Quicknet card)
G.729 (Windows only: requires VoiceAge library

5.8 - What video codecs are supported by OPAL?

H.261
H.263
CU-30

5.9 - Where can I get more information on plugin codecs?

See http://www.voxgratia.org/docs/codec_plugins.html

5.10 - Why does a call using a compressed audio codec use much more bandwidth than expected?

The "headline" bitrate of a audio codec does not include the overhead added by RTP and UDP encapsulation. This overhead means that a compressed code like GSM (with an advertised bit rate of 13200 bits/second) actually consumes 29200 bits/second, while an uncompressed codec like G.711 (with an advertised bit rate of 64kbps) actually consumes 75kbps.

For a detailed explanation of how to calculate the actual bit rate for an audio codec, see http://www.voxgratia.org/docs/codecbw.html

5.11 - What is the effect of changing the number of frames per packet for an audio codec?

Increasing the number of frames per packet will increase latency but decrease bandwidth. Decreasing the number of frames per packet will decrease latency but will increase bandwidth.

See http://www.voxgratia.org/docs/codecbw.html for a more detailed explanation of why this occurs.

5.12 - Why am I getting bad audio quality even though I am using G.711?

See 7.8

5.13 - Why am I getting bad audio when using the G.729 codec?

See 7.9

5.14 - How do I get the same codec in each direction when making a call?

This is an old problem, and one that is not easy to solve.

Firstly, it is perfectly legal to have asymmetric codecs in H.323. So what we are trying to do is outside the specification

Having said this, OPAL tries hard to get symmetric codecs but it is not always possible, especially if using slow start and the other end has a very different codec priority list.

The only guaranteed way is to have only one codec in the list. If this is not possible, then having the same codec priority, and using fastStart, also helps.

5.15 - Why are there so many Speex capabilities?

These Speex capabilities can be divided three different groups:

Narrow and wide band codecs, using original OpenH323 identifier
Narrow and wide band codecs, using identifier specified in Speex draft RFC
Windows compatible narrow codec

There are two sets of Speex capabilities because the draft Speex RFC specified a format for the H.323 non-standard capability string that was incompatible with the format used by existing OPAL implementations. Thus, the only way to preserve backwards compatibility with old applications while still conforming to the new standard was to include both sets.

The original OpenH323 capability identifiers were removed from OPAL in August 2006.

For more information on the Speex Draft RFC, see http://www.speex.org/drafts/draft-herlein-speex-rtp-profile-02.txt

5.16 - Does OPAL support wide-band codecs?

Yes, via the plugin codec interface (see http://www.voxgratia.org/docs/codec_plugins.html). Speex wide-band has already been implemented via this interface in the current development code

5.17 - Can I use the H.263 video codec in my program?

The answer to this question is either no, yes, or maybe depending on who you are.

Firstly, I am not a lawyer. Any opinions expressed here are mine alone and should not be construed as an offer of legal advice. Your mileage may vary. Void where prohibited. Some settling of contents may occur during shipping.

Now that is out of the way, it is important to understand that there are actually two issues to be resolved: copyright and patents.

There is no copyright issue as far as the FFMPEG codec library is concerned (the one that OpenH323 uses). The FFMpeg library is LGPL, and so can be used with the non-(L)GPL OpenH323, provided we load it at run-time (we do), and provided we make any changes available as per the terms of the LGPL (we do that too).

As expected, the patent issue is not as clear.

According to the site at http://www.mpegla.com it is legal to sell up to 50,000 MPEG4 decoder or encoder licenses in one year without royalties. See http://www.mpegla.com/m4v/m4vweb.ppt for more information. MPEG4 is essentially H.263+, so you would expect that the H.263 code would just be a subset of the MPEG4 code. Apparently this is not the case, so this licensing arrangement probably does not apply. Or at least, that's what some people say - others say different. The situation for you could well depend on the patent law in your part of the world.

In the end, there is no definitive answer saying that ffmpeg is safe to use, or not. You'll have to make up your own mind and get your own advice.

Feel free to contact the author if you have any additional information on this subject

6. DOCUMENTATION

6.1 - Where can I get a design document for OPAL?

TBD

6.2 - Where can I find the help file for OpenPhone?

There is no help file (yes - we know there is a link for one). If you write one, feel free to post it to the list

6.3 - Where can I find user manuals for the OPAL programs?

In most cases, there are no manuals. Help on options can be found by running the program with the "--help" option.

6.4 - Is there a programming tutorial on OPAL?

TBD

6.5 - Is there documentation on audio codec plugins?

Yes - see http://www.voxgratia.org/docs/codec_plugins.html

6.6 - Where can I get documentation on the API for PTLib and OPAL?

The header files for OPAL and PTLib contain API documentation in the Doc++ format. The recommended tool for converting the header files into documents is Doxygen (see http://www.doxygen.org) which is much faster and more accurate than the original Doc++ (see http://docpp.sourceforge.net).

To create the documentation for any particular version of PTLib or OPAL, run the command "make docs" in the "ptlib" or "opal" directories. A directory called "html" will be created that contains the documentation in HTML format. Doxygen can also be used to create documents in RTF and LaTex format, as well as the compressed HTML format (.CHM) for Windows.

Links to on-line versions of the API documentation are available online

6.7 - What documentation is available for OPAL?

A list of all documentation available for OPAL can be found in the Wiki

6.8 - Where can I find specification documents for H.323 or SIP?

Copies of the specifications for H.323, H.225, H.245 and most related protocols can be found at http://www.packetizer.com/iptel/h323/standards.html

Copies of the specifications for SIP and most related protocols can be found at http://www.packetizer.com/voip/sip/standards.html

6.9 - Is there a document on the configure.exe program used for configuring OPAL and PTLib on Windows?

Yes, see http://www.voxgratia.org/docs/windows_configure.html

6.10 - Is there a document describing what SIP features are supported by Opal?

Yes, see SIP features

7. USING OPAL

7.1 - When I make a call I get audio in only one direction. What is the problem?

You are probably behind a firewall and are trying to make a call to someone on the other side... See your software documentation for how to solve this problem

7.2 - I am behind a firewall and cannot receive incoming calls? Why not?

Incoming H.323 calls require incoming TCP connections on port 1720.

Incoming SIP calls require incoming UDP connections on port 5060.

Make sure that your firewall is passing incoming connections on those ports to your client, and that your machine supports operation behind a firewall.

7.3 - I can establish a connection but no audio is transferred. What is wrong?

There are a number of possible reasons for this:

Correct sound card not selected.
Sound card muted or volume set to zero.
Microphone does not work.
A firewall is blocking media packets.
For Linux, IP security is blocking the media ports.
The two endpoints do not share a common codec.

7.4 - How do I call NetMeeting with an OPAL client?

NetMeeting can inter-operate with an OPAL client using only a few audio and video codecs. These codecs are G.711 for audio and H.261 or H.263 for video.

The G.711 audio codec is available as an Open Source implementation and should be available on all OPAL endpoints that have audio enabled. It requires a 64 kbps connection and is only available in NetMeeting if it is configured for LAN bandwidth.

The H.261 video codec is available as an Open Source implementation should be available on all OPAL endpoints that have video enabled. The H.263 video codec, which used less bandwidth and provides better quality, may be available if the optional support has been enabled and the required external library is available.

Several people have added new Open Source audio codecs to NetMeeting that use much lower bandwidth:

GSM - it is possible to enable GSM codec under Netmeeting, but the previous instructions on how to do this are no longer available. If you have a reference for this, please email craigs@postincrement.com
SpeexW - OPAL supports the SpeexW codec that can be added to NetMeeting. See http://www.republika.pl/roed/speexw/ for more information

NetMeeting contains proprietary codecs such as G.723.1 that may be available on some OPAL clients. For example, MyPhone (see http://myphone.sourceforge.net) contains code that allows use of the MS-ACM G.723.1 codec on a Windows client. See 5.4 for more informatio

7.5 - I hear an echo when I speaking on a H.323 call - what is wrong?

The echo is most likely caused by audio coming out the speaker being picked up by the microphone. Either move the speaker and microphone further apart, reduce the speaker volume, or (best of all) use a headset or handset.

7.6 - How can I test whether my client is working?

A recorded message can be heard by making a call to h323.voxgratia.org. This service supports the Speex, iLBC, GSM, LPC-10 and G.711 codecs. A gatekeeper also available at gk.voxgratia.org on port 1719. See http://www.voxgratia.org/docs/test_systems.html#endpoint for more information

7.7 - I'm sure I have found a problem with OPAL - how do I report it?

See 4.10

7.8 - Why am I getting bad audio even though I am using the G.711 codec?

G.711 should sound as good as a normal phone call, because it is the same codec as used for ISDN and in telco switches. If you are not getting good audio, then you probably have one of the following problems:

your network is heavily congested. Try increasing the jitter buffer size.
your machine is too busy, or has a congested network interface. Close down other network-based, or sound-based applications on the same machine.
G.711 may need as much as 75kps on a packet switched network, not 64kbps as commonly thought. (See http://www.voxgratia.org/docs/codecbw.html for a more detailed explanation of why this is so). Make sure that you are not using a low-speed link (such as dialup modem) that has sufficient bandwidth
your sound card uses small buffers. If you are using ohphone, try using the "--sound-buffers" option to increase the number of buffers (the default value is 3)

7.9 - Why am I getting bad audio when using the G.729 codec?

G.729 uses a small packet size(10ms) which can cause problems with certain sound cards that use small sound buffers. If you are experiencing broken audio when using the G.729 codec, increase the number of sound buffers from the default value of 3. How this is done will depend on your client, but with ohphone it is done using the "--sound-buffers" option.

7.10 - Not used

7.11 - How does OPAL support ENUM dialling?

OPAL automatically implements ENUM dialling (RFC 2916) for endpoints under the following conditions:

the destination number contains only digits
the destination address does not specify a gateway or gatekeeper
the endpoint is not configured to use a gatekeeper for address resolution

By default, the following domains will be used (in order) to resolve a DN using ENUM:

e164.voxgratia.net e164.org e164.arpa

This default path can be overridden by setting the PWLIB_ENUM_PATH environment variable to a list of domains separated by semi-colons (";") on Windows, or colons (":") on Unix

7.12 - I am getting "Blocked" or other incorrect results when using STUN - how do I fix this?

OPAL contain support for the STUN (Simple Traversal of UDP Through NAT) protocol to simplify making calls from behind a NAT firewall. This protocol uses a remote STUN server to assist a client in detecting what kind of NAT is being used.

The STUN client code uses a timeout of 5000ms which gives reliable results, with the possible side effect of increasing setup time for hosts with busy or low speed connections.

7.13 - What are the different firewall types reported by STUN, and what do they mean?

OPAL and PTLib support the STUN protocol (see RFC 3489) for detecting and interoperating with NATs and firewalls. The STUN protocol can detect several different NAT and firewall configurations, but only some of these configurations support VoIP functions. The detected NAT types are as follows:

NAT Type	NAT	Port Restrictions	Address Type	Supports VoIP	Description
BlockedNat	Unknown	Unknown	Unknown	No	Host has no connectivity that can be determined.
PartialBlockedNat or UnknownNat	Uknown	Unknown	Unknown	Unknown	Unknown NAT type
OpenNat	No	No	Public	Yes	Host has a public IP address and has unrestricted access to the Internet with no firewall or NAT restrictions
SymmetricFirewall	No	Yes	Public	Yes (see note 1)	Same as OpenNAT, but some network entity (probably a firewall) is enforcing symmetric UDP connections. This means that a remote host can only send to an address/port on the source host if, and only if, it has previously received a connection from the source address/port.
ConeNat	Yes	No	Private	Yes	Each source address/port pair is mapped to a unique external address/port pair. Any external host can send to the internal host via the external address/port.
RestrictedNat	Yes	Yes	Private	Yes (see note 1)	Same as Cone, except an external host can only send to the internal host if, and only if, the internal host has previously sent a packet to the external host address.
PortRestrictedNat	Yes	Yes	Private	Yes (see note 1)	Same as RestrictedNat, except an external host can only send to the internal host if and only if, the internal host has previously sent to the external host address and port
SymmetricNat	Yes	Yes	Private	No	Each source address/port & destination address/port four-tuple is mapped to a unique external address/port pair. Only the destination address/port can send to the internal address/port.
Note 1: this NAT type requires the endpoint behind the NAT to send audio/video before it will receive any audio/video. This may not be possible in call cases.

The STUN requires the use of an external STUN server. Reitek S.p.a has generously provided a STUN server for use by Vox Gratia users which can be found at stun.voxgratia.org.

7.14 - Why I am seeing messages like "RTP Packet from SSRC=xxxxxxxx ignored, expecting SSRC=yyyyyyyy" with audio only in one direction?

The one-way audio and the warning message are caused by the endpoint changing the RTP SSRC identifier in the middle of a call. While strictly speaking this is not illegal, it is a strange thing for the endpoint to do as this makes the endpoint look like a hostile endpoint is attempting to insert audio into the session.

Unfortunately, some endpoints do change the SSRC identifier mid-call and by default OPAL will detect the condition and ignore the new data. The warning message above will be displayed when this condition occurs.

If you need to interoperate with endpoints that change SSRC mid-call, you can disable the checking of SSRC identifiers by editing the file opal/src/rtp/rtp.c. Look for a line of code in the function RTP_Session::RTP_Session as follows:

 ignoreOtherSources = TRUE;

Change this to:

 ignoreOtherSources = FALSE;

7.15 - How many simultaneous calls can OPAL handle?

The short answer is that it depends on your application, and the amount of CPU you have.

A more precise answer is that without any modification, a standard OPAL application on Linux that handles both signalling and media will hit the per-process file handle limit at about 80 simultaneous calls. By increasing the per-process file handle limit to 16384 (using "ulimit") the maximum call density is around 1300 calls. If the calls always use H.245 tunnelling, this will increase to 110 and 1800. If the calls are signalling only, the limits are 330 and 5400.

The limits on Windows are around 1000 calls regardless of the call type.

An OPAL application can increase these limits further by enabling signalling aggregation. This feature is not yet available on OPAL.

A detailed description of the problem and the aggregation solution is available in the whitepaper "Increasing the maximum call density of OpenH323 and OPAL" (see http://www.voxgratia.org/docs/call%20thread%20handling%20model%201.0.pdf)

7.16 - Why am I getting broken audio under Windows Vista?

The sound drivers in Windows Vista require more buffers than identical hardware under Windows XP or Linux. If you are getting broken audio, try increasing the number of sound buffers to 8 or 10.

Simpleopal does this by default. Other Opal-based software can do this by adding the following code to the initialisation of the PCSS endpoint:

  pcssEP->SetSoundChannelBufferDepth(10);

8. OPAL applications

8.1 - What other projects use OPAL?

The following Open Source projects are known to use OPAL or OpenH323:

Ekiga (formerly known as GnomeMeeting) - http://www.ekiga.org
Client program for Windows, Linux, and other Unix platforms based on OPAL
Xmeeting - http://xmeeting.sourceforge.net/
Client program for MacOSX based on OPal

If you know of any other projects, please email craigs@postincrement.com

8.2 What commercial and closed-source software uses Opal

The following commercial software is known to use OPAL:

Gridborg HMP - http://www.uniqall.com
A software based media controller based on OPAL that supports voice and fax

If you know of any other products, please email craigs@postincrement.com

8.3 - What is the status of the OpenMCU program?

OpenMCU was originally created in May 2000 by Craig Southeren as a experiment to investigate some ideas about how an audio MCU might work. A description of the original motivations can be found at http://www.southeren.com/blog/archives/000050.html.

A new project was started in March 2006 with the support of Stonevoice to restore video functionality to OpenMCU. In June 2006, OpenMCU 2.2.0 was released with full support for both audio and video including the H.261 and H.263 codecs.

8.4 - How do I use OPAL with Asterisk?

See the WoomeraVoip project

9. Programming

9.1 How do I create a program that uses OPAL for call control, but uses an external RTP device?

TBD

9.2 - How do get a list of the codecs supported by OPAL?

TBD

9.3 - When I enable PMEMORY_CHECK, I see all sorts of memory leaks reported. How do I fix these?

There is a define called PMEMORY_CHECK that enabled all sorts of code in PTLib to check memory blocks allocated by the code. But this is turned off by default (even in debug mode) because the code it uses is pretty stupid. Not only does it slow down the entire stack by a significant amount, but it reports all sorts things as memory leaks when they really aren't. We got tired of people going into a panic when they saw the words "memory leak" and then having to explain why this was not a problem, so we just disabled it.

First of all, let's be clear what a memory leak is. The jargon file (see http://www.catb.org/~esr/jargon) defines a memory leak as:

An error in a program's dynamic-store allocation logic that causes it to fail to reclaim discarded memory, leading to eventual collapse due to memory exhaustion.

By this definition (which I agree with), a memory leak it is not just a memory block that is never freed, but it a problem with memory allocation that leads to memory exhaustion. This is an important distinction, because there are lots of places in PTLib, OpenH323 and OPAL where memory is allocated, but never freed, and these do not (and never will) lead to memory exhaustion because they are only allocated once and the reused for the lifetime of the program. The PFactory code is a good example of this.

It is these memory blocks that cause PMEMORY_CHECK to be a pain. It reports every one of these memory allocations as a memory leak even though they are not causing any problems. So why don't we just ensure that these memory blocks are cleaned up? Two reasons - firstly we don't have time to spend on issues that are not real problems; and secondly, it can be difficult to determine exactly when some of these memory blocks should actually be freed in order to avoid causing problems during shutdown. So we just choose to avoid the issue.

9.4 - What is the status of call aggregation in OPAL?

PTLib has the low-level support for socket aggregation. It only works on Windows. There is no reason why it could not be extended for Linux, other than time :)

OpenH323 (and presumably H323plus) can use the PTLib aggregation support for RTP and for H.323 signaling.

Opal can only use the PTLib aggregation support for RTP.

Opal cannot yet use the aggregation support for H.323. Again, time is the only constraint.

Opal does not yet support SIP over TCP, so it definitely does not support aggregation for SIP over TCP

Opal does not NEED the PTLib aggregation support for SIP over UDP, because the code already uses a single thread and socket

10. USING OPAL

10.1 - Not used

10.2 - Not used

10.3 - Not used

10.4 - How do I use SimpleOPAL to make a call?

Most of the command line options for SimpleOPAL are fairly obvious, but some examples are always useful:

The following command makes a H.323 call to h323.voxratia.org without using a gatekeeper.

 simpleopal -n h323:h323.voxgratia.org

The following command makes a SIP call to a remote endpoint without using a registrar.

 simpleopal -n sip:192.168.1.247

To listen for incoming calls, use the "-l" option instead of the destination address.

For information on making calls to telephone numbers with SimpleOPAL, see 10.7 below

10.5 - Not used

10.6 - Not used

10.7 How do I use OPAL to make a call to a telephone number?

To make calls to a telephone number, you will need to use a service that provides a gateway between SIP or H.323 calls and the public switched telephone network. There are several such networks - some of these are free and some charge for calls. Instructions on using several such networks can be found below. Please email craigs@postincrement.com if you have information on any other calling services that are compatible with OPAL or OpenH323

Free World Dialup - http://fwd.pulver.com

This free service allows calls to a wide variety of SIP networks as well as US 1800 and 1866 numbers. The following command line can be used to make a test call to any FWD destination

 simpleopal -H -u userid -p password --register-sip fwd.pulver.com sip:number@fwd.pulver.com

Broadvoice - http://www.broadvoice.com

This subscription service offers both incoming and outgoing calls via SIP. The following command can be used to make outgoing calls:

 simpleopal -H --register-sip proxy.broadvoice.com \ 
 --sip-proxy proxy.broadvoice.com \ 
 --sip-domain sip.broadvoice.com \ 
 -D *LBC* -D *Speex* \ 
 -u userid -p password \ 
 sip:number@sip.broadvoice.com

Note that is necessary to disable the Speex and iLBC codecs when using Broadvoice as the service will timeout or refuse calls containing these codecs.

Gizmoproject - http://www.gizmoproject.com

This service offers free outgoing calls to many countries and incoming calls from landlines for a fee. The following command line can be used to listen any destination

 simplopal -H -u userid --password password --register-sip proxy01.sipphone.com sip:number@proxy01.sipphone.com

International (non-US) destination can be called by prefixing the number with the "+" character, such as "sip:+61243654666@proxy01.sipphone.com"