Guide to NeVoT 3.34

NeVoT icon


Audio conferences with NeVoT require two or three parts:
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.
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.


This file, doc/nevot.html, contains step-by-step instructions to running NeVoT. The messages exchanged between NeVoT and the conference controller are described in a note (This note is part of the isc documentation.) RTP is described in RFC 1889 and RFC 1890.

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
    HP HPUX /usr/audio/examples/acontrol
    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
    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

Mainly for use with conferencing tools like sd, NeVoT takes the following 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.
Use synchronous mode for display server.
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, when local multicast connects applications. The port can be any number; 5010 is used by default.

Configuration and X Resources

The defaults for NeVoT are contained in the startup file .nevotrc located in the home directory. Normally, you should not need to create or edit this file.

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.



NeVoT was written by Henning Schulzrinne, while he was at the University of Massachusetts, AT&T Bell Laboratories and now GMD Fokus.


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

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Last modified: Sat, 10 Feb 1996