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NAME

       Network Audio System - a portable, network-transparent audio system

SYNOPSIS

       The  Network  Audio  System  service  is a network-transparent system developed at Network
       Computing Devices for playing, recording, 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.

DESCRIPTION

       The Network Audio System 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  various  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 programming library.

       The Network Audio System service supports a variety of the common formats  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
       environments, 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 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 Window 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  compatible  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 Network Audio System 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 pre-recorded sound files or to
               record new sound files.  It  provides  a  simple  control  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 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.

       aupanel This program provides an X-based window-oriented interface allowing  the  user  to
               adjust the attributes of the devices provided by the Network Audio System service.

       auedit  This  program  provides  an X-based window-oriented interface allowing the user to
               edit audio files.

       auconvert
               This program allows the user to perform various  conversion  operations  on  sound
               files.

       auphone This  program  provides an X-based window-oriented interface allowing two-way real
               time voice communication between two audio servers.

       aurecord
               This program is used to record audio data from an audio server into a file.

       auwave  This program provides an X-based window-oriented interface demonstrating  the  use
               of waveform elements.

AUDIO FILES

       The  audio programming library and utility programs can be used to read and write files in
       any of the following file formats:

       Sun/NeXT
              These files typically have a '.au' or '.snd' extension.  They are usually  produced
              by Sun or NeXT workstations.

       Creative Labs
              These  files  typically  have  a '.voc' extension.  They are usually produced by by
              Soundblaster audio cards on IBM PC compatible computers.

       Microsoft WAVE
              These files typically have a '.wav' extension.  They are usually produced by IBM PC
              compatible computers.

       AIFF
              These  files  typically  have  an  '.aiff'  or  '.aif' extension.  They are usually
              produced by SGI workstations or Apple computers.

       Amiga IFF/8SVX
              These files typically have an '.iff' extension.

       Due to the nature of the file formats, only the Sun/NeXT file format can be piped  through
       standard  input  and/or  standard output.  The convention for specifying standard input or
       standard output is to use a hyphen ("-") as the file name.

PROGRAMMING

       Application developers may create their own audio clients using the Network  Audio  System
       programming library.

ENVIRONMENT VARIABLES

       The following environment variables are used by Network Audio System programs:

       AUDIOSERVER
               This  specifies  the  name  of  default  audio  server  to  contact  if no name is
               explicitly given on the command line.

       DISPLAY This specifies the name of an X Window System display that should  be  assumed  to
               also have a corresponding Network Audio System server.

SEE ALSO

       auplay(1),  audemo(1),  audial(1), autool(1), auinfo(1), auctl(1), auscope(1), aupanel(1),
       auedit(1), auconvert(1), auphone(1), aurecord(1), auwave(1)

       Network Audio System Overview and Programmers Guide

COPYRIGHT

       The following copyright and permission notice applies to all files in  the  Network  Audio
       System  application  programming libraries and example programs provided in source form by
       Network Computing Devices:

       Copyright 1993, 1994 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 documentation, and that the name Network Computing Devices, Inc. not be used
       in advertising or publicity pertaining to distribution of this software without  specific,
       written prior permission.

       THIS  SOFTWARE  IS  PROVIDED  `AS-IS'.   NETWORK  COMPUTING  DEVICES,  INC., DISCLAIMS ALL
       WARRANTIES WITH  REGARD  TO  THIS  SOFTWARE,  INCLUDING  WITHOUT  LIMITATION  ALL  IMPLIED
       WARRANTIES  OF  MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, OR NONINFRINGEMENT.  IN
       NO EVENT SHALL NETWORK COMPUTING DEVICES, INC., BE  LIABLE  FOR  ANY  DAMAGES  WHATSOEVER,
       INCLUDING  SPECIAL,  INCIDENTAL  OR CONSEQUENTIAL DAMAGES, INCLUDING LOSS OF USE, DATA, OR
       PROFITS, EVEN IF ADVISED OF THE POSSIBILITY THEREOF,  AND  REGARDLESS  OF  WHETHER  IN  AN
       ACTION  IN  CONTRACT,  TORT OR NEGLIGENCE, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
       PERFORMANCE OF THIS SOFTWARE.

TRADEMARKS

       NCD, NCD Display Station, and NCDware are all trademarks  of  Network  Computing  Devices,
       Inc.

       X Window System is a trademark of the Massachusetts Institute of Technology.

AUTHORS

       Greg Renda, Jim Fulton, David Lemke

                                                                          NETWORK AUDIO SYSTEM(1)