README version 22jun2005

Welcome to intercom, a Voice over IP speaker-phone conference 
application. The application can:
- dial a intercom partner via short-dial buttons
- make a RTP connection to transport your voice over IPv4
- make a telephone conference
- support wideband codec (16kHz sample frequency)

Intercom is still very limited. But the things it can do, it does
very well!


Modify file ~/.intercom.conf for your short-dial labels
and your IP-addresses.

To start the application enter

  intercom
  
Read shell script /usr/local/bin/intercom to get an idea of what is 
going on. For better echo cancellation start intercom with the -m or
-l option.

For a first test talk to yourself by clicking the button for your own
IP-address, e.g. EDDF TEC2 if your computer is 192.168.1.2.
The button should become green.
Attention: A short click (less then 300ms) toggles on/off, a long
click works as push-to-talk.

ATTENTION: The intercom application needs PCM out for playback. This
hardware device is used also by other sound programs like MP3 players 
(e.g. xmms) or WAV record/playback programs like sweep and audacity. The
intercom application blocks (freezes) as long as another program uses 
PCM out. There are ways around this like using sound daemons aRTs or 
esound. But this is outside of the intercom application.

If you dial another intercom station, you get an one-way connection from
your microphone to the loudspeaker of your intercom partner. If your 
partner clicks on the correct button (the magenta one), both of you have 
a two-way communication. Now you or your partner can dial more intercom
stations to make a conference with maximum 6 stations.
Note: Start intercom with the -t option to get "everybody can talk and 
listen with everybody else".


Read the file 
http://home.arcor.de/andreadrian/intercom/draft-conference-01.txt 
for more information.


Supported royalty free Codecs:
For License see ITU-T G.191 or IETF RFC3951

Narrowband (8kHz sample frequency):
-----------------------------------
IETF iLBC           15.2kBit/s  Global IP Sound iLBC Public License
ITU-T G.711 A-law   64kBit/s    ITU-T SOFTWARE TOOLS' GENERAL PUBLIC LICENSE
ITU-T G.711 u-law   64kBit/s    ITU-T SOFTWARE TOOLS' GENERAL PUBLIC LICENSE
ITU-T G.726 32kbs   32kBit/s    ITU-T SOFTWARE TOOLS' GENERAL PUBLIC LICENSE
3GPP GSM            13.2kBit/s  ITU-T SOFTWARE TOOLS' GENERAL PUBLIC LICENSE

Wideband (16kHz sample frequency):
----------------------------------
Speex               27.8kBit/s  Xiph.org license (BSD license variant)

Author: Andre Adrian
E-Mail: Andre dot Adrian at dfs dot de
Postal: DFS Tower Frankfurt
        Mr. Andre Adrian
        Flughafen Gebaeude 501
        60549 Frankfurt, Germany