NCDAUDIO(1) USER COMMANDS NCDAUDIO(1)
NAME
NCDaudio - a portable, network-transparent audio system
SYNOPSIS
The NCDaudio service is a network-transparent system
developed at Network Computing Devices for playing, record-
ing, and manipulating audio data over a network. It uses
the client/server model to separate application code from
the software drivers needed to control specific audio input
and output devices.
NCDaudio is a trademark of Network Computing Devices, Inc.
DESCRIPTION
The NCDaudio service provides applications with the ability
to send and receive audio data such as voice, sound effects,
and music in a network environment. A audio server inside
the desktop terminal or personal computer controls the vari-
ous input and output devices in response to messages sent
from client programs running on other hosts.
A variety of utility programs are provided that can be used
to play or record audio using shell scripts or command-line
procedures. More ambitious applications can communicate
directly with the audio server using a C-language program-
ming library.
The NCDaudio service supports a variety of the common for-
mats used to store sound data. Audio inputs and outputs can
run at a any of a range of sampling rates. The audio server
automatically converts all data to the designed format or
rate.
Streams of data from multiple inputs can be mixed together
and directed to any attached output device. Sounds that are
used many times can be stored in the server so that they do
not need to be transmitted over the network each time they
are played. Furthermore, inputs can be hooked directly to
outputs (for example, a CD player can be connected to a set
of speakers) so that data can be played without requiring
any client intervention or network traffic.
AUDIO SERVER NAMES
Each audio server has a name that is used by applications in
establishing a connection. The format of the name depends
upon the type of network being used. In TCP/IP environ-
ments, audio server names look like:
tcp/hostname:portnum
where hostname is the name or numeric IP address of the
desktop machine to be contacted and portnum is the port
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number on which the server is listening. If the ``tcp/''
prefix is not given, 8000 is automatically added to portnum
so that the audio server name is compatible with the X Win-
dow System display name.
In DECnet environments, audio server names look like:
decnet/nodename::num
where nodename is the name or numeric DECnet address of the
desktop machine to be contacted and num is the DECnet task
AUDIO$num. If the ``decnet/'' prefix is omitted, it is
automatically added so that the audio server name is compa-
tible with the X Window System display name.
Most audio utilities accept a command line argument -audio
servername for specifying the audio server to be contacted.
% auinfo -audio tcp/ncdunit:8000
If no server is specified on the command line, the
AUDIOSERVER environment variable is checked to see if a name
has been stored there. Otherwise, the DISPLAY environment
variable used by X Window System applications is checked and
the corresponding audio server is used.
SAMPLE PROGRAMS
Several sample programs that use the NCDaudio service are
provided by NCD:
auplay This program simply plays the files listed on its
command line. It is typically used from shell
scripts, command-line procedures, or other programs
that just need to ``dump'' sound data to the audio
server.
audemo This program allows the user to select and play
prerecorded sound files. It provides a simple con-
trol panel for dynamically changing the volume while
a sound is being played and for aborting a sound.
audial This program generates North American telephone
touch tones correspond to a given string. audial
can also recognize touch tones and produce the
corresponding string.
autool This program is compatible with the Sun audiotool
program and is typically used to play prerecorded
sound files. Unlike auplay it provides a graphical
interface to allow the user to replay or cancel the
data.
auinfo This program lists information describing the
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capabilities of an audio server.
auctl This program can be used to change various device
parameters.
auscope This program is an audio protocol filter that can be
used to view the network packets being sent between
an application and an audio server.
sndtoinclude
This utility translates audio data stored in .SND or
.AU format into a format that can be included into
C-language programs.
wavtosnd
This utility translates audio data stored in .WAV
format into .SND format.
AUDIO FILES
The audio programming library and utility programs can be
used to read and write files in either the .SND (sometimes
called .AU) or .WAV formats. The former is typically used
on Sun platforms; the latter is usually used on PCs.
PROGRAMMING
Application developers may create their own audio clients
using the NCDaudio programming library. The document NCDau-
dio Overview and Programmers Guide is available from NCD
Technical Support.
ENVIRONMENT VARIABLES
The following environment variables are used by NCDaudio
programs:
AUDIOSERVER
This specifies the name of default audio server to
contact if no name is explicitly given on the com-
mand line.
DISPLAY This specifies the name of an X Window System
display that should be assumed to also have a
corresponding NCDaudio server.
SEE ALSO
auctl(1), audemo(1), audial(1), auinfo(1), auplay(1),
auscope(1), autool(1), NCDaudio Overview and Programmers
Guide
COPYRIGHT
The following copyright and permission notice applies to all
files in the NCDaudio application programming libraries and
example programs provided in source form by Network
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Computing Devices:
Copyright 1993 Network Computing Devices, Inc.
Permission to use, copy, modify, distribute, and sell this
software and its documentation for any purpose is hereby
granted without fee, provided that the above copyright
notice appear in all copies and that both that copyright
notice and this permission notice appear in supporting docu-
mentation, and that the name Network Computing Devices, Inc.
not be used in advertising or publicity pertaining to dis-
tribution of this software without specific, written prior
permission.
THIS SOFTWARE IS PROVIDED `AS-IS'. NETWORK COMPUTING DEV-
ICES, INC., DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS
SOFTWARE, INCLUDING WITHOUT LIMITATION ALL IMPLIED WARRAN-
TIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE,
OR NONINFRINGEMENT. IN NO EVENT SHALL NETWORK COMPUTING
DEVICES, INC., BE LIABLE FOR ANY DAMAGES WHATSOEVER, INCLUD-
ING SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES, INCLUDING
LOSS OF USE, DATA, OR PROFITS, EVEN IF ADVISED OF THE POSSI-
BILITY THEREOF, AND REGARDLESS OF WHETHER IN AN ACTION IN
CONTRACT, TORT OR NEGLIGENCE, ARISING OUT OF OR IN CONNEC-
TION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
TRADEMARKS
NCD, NCDaudio, NCD Display Station, and NCDware are all
trademarks of Network Computing Devices, Inc.
X Window System is a trademark of the Massachusetts Insti-
tute of Technology.
AUTHORS
Greg Renda, Jim Fulton, David Lemke
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