Guide to NeVoT 3.34

• Introduction
• Features
• Installation
• Documentation
• Basic Operation
• Command Line Arguments
• Configuration and X Resources
• Common Problems
• Future Work
• Acknowledgements
• Author
• Copyright

Introduction

nevot/nevotd:

The audio media agent. It obtains audio samples from the workstation and sends them as packets on attached networks. It also receives packets and plays the audio samples on the workstation audio device. Each instance of NeVoT can handle one or more audio conferences. nevot has a Tk user interface. nevotd is a daemon, without any graphical user interface, but the same capabilities as nevot.

a conference controller:

It establishes conferences and then displays participants. An example of such a controller is isc, described separately.

pmm:

If a system does not support local multicast, the message replicator pmm is used. It distributes messages between the conference controller like isc and the media agents, e.g., NeVoT. There is one instance of the message replicator per host.

Documentation

A University of Massachusetts technical report is also available. It describes basic issues and an earlier version of NeVoT.

A short note explains some of the internal workings of NeVoT.

Basic Operation

1. If you want to adjust the play or recording volume or change the input and output ports, you need to run a separate application. tkaudio exists for all NeVoT-supported platforms, but you may also use the following:

   Vendor	OS	application
   DEC	OSF
   HP	HPUX	/usr/audio/examples/acontrol
   IBM	AIX
   PC	Linux
   SGI	Irix	apanel
   Sun	SunOS 4.1.x	gaintool
   Sun	Solaris 2.x	/usr/demo/SOUND/bin/gaintool, /usr/openwin/bin/audiocontrol

2. Media agents and conference controllers are connected through a message replicator or by local multicast. For most applications and systems, local multicast is recommended. If you cannot use local multicast, you can start a replicator called pmm by typing

   pmm &
   

   Adding the -d 1 flag displays incoming and outgoing messages.
3. Typically, NeVoT is started by the conference controller. To start NeVoT by itself, type

   nevot
   

   A rectangular window with buttons labeled Settings and Quit should appear. As usual, you can add the -display option to change the X display being used. The -background or -bg option changes the background color (X resource class Background). The command line option -help displays all available options.
4. The Settings menu button puts up a menu of audio engine parameter settings, for silence suppression, VU display, automatic gain control, debugging, and the like. Normally, you should not have to change these. Any changed settings are not saved when leaving NeVoT.
5. You cannot join conferences from within the NeVoT audio engine. See the documentation for your conference controller for details on how to create or join a conference.

Command Line Arguments

-background, -bg color

Background color for window.

-display host:display

X Display to use.

-geometry size

Initial geometry of NeVoT window.

-name application name

Name to use for application.

-sync

Use synchronous mode for display server.

-help

Lists above standard command line arguments.

-p protocol/address/port

Configures communication between components. protocol can be either udp, for using multicast, or tcp, when pmm is running. address is typically localhost when pmm is being used, a multicast address, such as 225.2.0.1, when local multicast connects applications. The port can be any number; 5010 is used by default.

Configuration and X Resources

NeVoT uses the Tk X resource mechanism. Definitions in .Xdefaults are read on application start-up only if the X server resource database utility xrdb is not used. Often, .Xdefaults is read by xrdb on X server startup and thus any changes in that only take effect when restarting the X server. NeVoT defines itself as class ``NeVoT'',

Some useful examples:

Nevot*background: lightgray
Nevot*Font: fixed
Nevot.verbosity: 0

Note that resource nevot*background differs subtly from Nevot*background: the former only applies to application instances with application name nevot, while the latter applies to any instance with class name Nevot. In particular, if you start several instances of nevot on a single display, nevot*background applies only to the first (the second instance will be named nevot #2), while Nevot*background applies to all.

Acknowledgements

Author

Copyright

Copyright 1991-1995 by AT&T Bell Laboratories and GMD Fokus; all rights reserved

Permission to use, copy, modify, and distribute this software and its documentation for research and educational purpose and without fee is hereby granted, provided that the above copyright notice appear in all copies and that both that the copyright notice and warranty disclaimer appear in supporting documentation, and that the names of the copyright holders or any of their entities not be used in advertising or publicity pertaining to distribution of the software without specific, written prior permission. Use of this software in whole or in parts for direct commercial advantage requires explicit prior permission.

The copyright holders disclaim all warranties with regard to this software, including all implied warranties of merchantability and fitness. In no event shall the copyright holders be liable for any special, indirect or consequential damages or any damages whatsoever resulting from loss of use, data or profits, whether in an action of contract, negligence or other tortuous action, arising out of or in connection with the use or performance of this software.