Guide to NeVoT 3.34
Audio conferences with NeVoT require two or three parts:
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.
- 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,
- 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.
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.
Mainly for use with conferencing tools like sd, NeVoT takes the
following command line arguments:
- 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:
- 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
Adding the -d 1 flag displays incoming and outgoing messages.
- 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.
- 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.
- 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.
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.
- -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
22.214.171.124, when local multicast connects applications. The
port can be any number; 5010 is used by default.
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:
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