NAME
xmit - Radio Free Ethernet transmitter
SYNOPSIS
xmit [ -h host
] [ -s service ] [
generic-tool-arguments ]
DISCLAIMER
This program is furnished on an AS IS basis as a demonstra-
tion of audio applications programming.
DESCRIPTION
xmit is the window-based Radio Free Ethernet transmitter. It
functions as a graphical front-end to the radio_xmit(6) pro-
gram, which it uses to read audio data from the audio device
(or a file) and broadcast it over the network. (For an over-
view of Radio Free Ethernet, please refer to the radio(6)
manual page.)
Before you can start broadcasting, you must configure a sta-
tion name. Clicking on the Station item brings up a station
edit panel that allows you to specify the station name and
broadcast characteristics for one or more stations. The Sta-
tion item brings up a menu of the stations that are config-
ured. Once you select a station, you may begin broadcasting
by pressing the Power button.
Ordinarily, the program broadcasts to the IP Multicast
address identified by the host name RadioFreeEthernet found
in the NIS hosts map. The -h host command-line option may be
used to specify an alternate host address or name to use for
the default IP Multicast address.
The Radio Free Ethernet tools use the port number identified
by the service name radio found in the NIS services map. The
-s service command-line option may be used to specify an
alternate service name or port number to use.
The following sections describe the individual panel con-
trols. In addition, online help is available by positioning
the pointer over the item in question and pressing the HELP
key.
Power toggles the state of the transmitter on and off. Since
this involves communicating with a running copy of the
radio_xmit program, this operation may take a few
seconds to complete. This button is only enabled when
a station name has been configured and selected.
Station
brings up a menu of the radio stations that have been
configured for broadcast. The Edit... entry brings up
a panel that may be used to add or modify the broad-
cast station configuration. Changes to the station
configuration parameters do not take effect until the
Add or Change button is pressed. If the the configura-
tion parameters are changed for a station that is
currently broadcasting, the new configuration will not
take effect until the station is powered off. Add,
Change, and Delete also cause the current station list
and program parameters to be written out to the ini-
tialization file.
Input Volume
may be used to manually adjust the audio input gain
level. It is only enabled when broadcasting data from
an audio device (as opposed to a pre-recorded file).
Auto Volume Adjust
enables an automatic gain control algorithm that moni-
tors the input volume level and adjusts it when the
audio data is too soft or too loud. The algorithm
tends to be cautious, lowering the volume quickly when
it is too loud, but raising the level slowly to avoid
the noise-pumping effects characteristic of cheap tape
recorders. This control is only enabled when broad-
casting data from an audio device. The station confi-
guration panel comes up by default in an abbreviated
form, displaying only the Station option. The plus
(+) button in the lower right corner causes the window
to expand to display additional transmit parameters
for the selected station. The following sections
describe all of the station configuration panel con-
trols:
Station
is a text field in which a four-letter station name
may be entered. The station name is used to identify
your broadcast program.
Sign-On File
specifies an audio file that is broadcast when the
transmitter is initially powered on.
Audio Input
specifies the source of audio data for the normal sta-
tion broadcast.
Sign-Off File
specifies an audio file that is broadcast when the
transmitter is powered off.
Auto-Shutoff
determines the action to be taken when the audio input
source is silent. When this option is enabled, the
station will automatically sign off if there has been
no audio input for a full minute. If this option is
disabled, the station will continue to broadcast sta-
tion identification packets, but will suppress the
broadcasting of audio data until some sound is
detected.
Audio Format
selects the audio data format that will be transmit-
ted. The uncompressed format causes 8000 bytes of
audio data to be broadcast each second. Compressed
data sends only 4000 bytes per second, but requires
more computation on both the transmitter and
receivers.
Multicast Addr
specifies the network broadcast address (see
radio_xmit(6) for more information on the IP Multicast
implementation). The special string BROADCAST causes
the program to transmit UDP Broadcast packets (which
will not be relayed over a network gateway).
Multicast Hops
specifies the number of network gateways that RFE
broadcast packets may traverse.
FILES
~/.radiorc
startup initialization file for radio and xmit
SEE ALSO
radio(6), radio_recv(6), radio_xmit(6)
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