usage.sgml

Intercom 是一个 Unix系统上灵活的语音传输软件。支持标准音频压缩比如GSM, G.711, and G.72x和其他音频编码。Intercom专为高速网络设计来传输高品质的语音

<!-- $Id: usage.sgml,v 1.1 2002/03/10 10:17:07 shane Exp $ -->

<chapter id="usage">
<title>Using Intercom</title>

<para>This chapter describes Intercom's basic usage.  Topics covered include
running the program, placing, receiving, and terminating calls and a brief
look at some of Intercom's call settings.</para>

<section id="usage-startup">
<title>Starting Intercom</title>

<para>Once Intercom has been installed on your system, simply typing
<command>intercom</command> at a command prompt should start the program. 
After a brief license text, you should be presented with the
<prompt>intercom: </prompt> prompt.  If the location where you installed
Intercom is not in your path, you will need to specify the complete path
when starting the program.  For example, if you installed Intercom into your
home directory, you would use something like
<command>$HOME/bin/intercom</command>.</para>

</section>

<section id="usage-cmdprompt">
<title>Introduction to the Command-Prompt</title>

<para>When Intercom is started and you are sitting at an <prompt>intercom:
</prompt> prompt, you are at what is known as the command-prompt.  By
entering commands at this prompt, you are able to control all of Intercom's
functions.  It is very similar to a Unix shell prompt with which you are
probably already familiar.</para>

<para>Intercom's commands are generally single words followed by optional or
required arguments depending on the command.  For example, the
<command>call</command> command instructs Intercom to place a call to a
remote party.  The first and possibly the most important Intercom command
you learn is the <command>help</command> command.  It displays a list of all
valid commands and a brief description of their function.  With most
commands, you can enter <command>help
<replaceable>command</replaceable></command> to get a more detailed usage
summary of that command.  For example <command>help call</command> would
display the usage information for the call command.  Using this help system,
one can usually pick up Intercom quite quickly.</para>

</section>

<section id="usage-call">
<title>Placing a call</title>

<para>By this point, I will assume you have someone also running Intercom
who you would like to call.  All you need is the remote party's host name or
IP address.  Once you have this information, try the following command at
the <prompt>Intercom: </prompt> prompt.</para>
<para><command>call
<replaceable>remote_hostname</replaceable></command></para>
<note><para>REplace <replaceable>remote_hostname</replaceable> with the actual
host name or IP address of the remote party.</para></note>

<para>If all goes well, Intercom should display a placing call message and
return you to a command-prompt.  At this point, Intercom is waiting for the
called party to either answer or reject the call.  To see how to do this,
read the following section of this chapter.  If you receive no response from the remote side, either positive or
negative, go ahead and type <command>hangup</command> to close the
call.</para>

<para>If your call is accepted, you will receive a message to that effect
and the audio path will immediately be established for two way
communication.  You should be able to both hear the remote party and he
should in-turn hear you.  Intercom is a <emphasis>full-duplex</emphasis>
application so there is no <phrase>push to talk</phrase> mode
available.</para>

<para>If the voice data is not getting through at all, the reason is
probably an improperly configured audio system.  Be sure that your audio
capture source is set to Mic and that your capture volume is high
enough.</para>

</section>

<section id="usage-answer">
<title>Handling an Incoming Call</title>

<para>When Intercom receives a call, you are presented with an Incoming call
notice.  It is then up to you whether you answer or reject it.  The notice
will contain the remote host-name or IP address and possibly the name of the
person calling if he has set the appropriate variables.  A typical incoming
call notice looks similar to the following</para>
<programlisting>
<prompt>intercom: </prompt>Incoming call from shane@192.168.1.2.
Use 'answer' to respond or 'hangup' to reject.
</programlisting>

<para>As is stated in the notice, you may use the <command>answer</command>
command to respond to the call or <command>hangup</command> to reject it. 
If the call is answered, the audio paths are immediately connected in both
directions and you should be able to both speak to and hear the remote
party.</para>

</section>

<section id="usage-hangup">
<title>Terminating a call</title>

<para>The <command>hangup</command> command is used to terminate a call. 
Both calls currently in progress or those waiting on user response can be
terminated through this command.  The <command>hangup</command> currently
does not accept any options and is as simple as they come.</para>

</section>

<section id="usage-defaults">
<title>A Word About Default Parameters</title>

<para>By default, Intercom is set to communicate over low-bandwidth links. 
It uses a sampling rate of 8000 samples per second compressed using the GSM
CODEC.  This consumes 13.2 Kbit/sec or 1.61 Kbytes/sec in either direction. 
If you have a high-speed connection, you can achieve much higher audio
quality by changing the compression format used and the audio sampling rate. 
This is discussed further in the next chapter.

</section>

</chapter>