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<html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>Music on Hold</title><link rel="stylesheet" href="styles.css" type="text/css" /><meta name="generator" content="DocBook XSL Stylesheets V1.69.1" /><link rel="start" href="index.html" title="Asterisk™: The Future of Telephony" /><link rel="up" href="asterisk-CHP-13.html" title="Chapter 13. Managing Your Asterisk System" /><link rel="prev" href="asterisk-CHP-13-SECT-5.html" title="Customizing System Prompts" /><link rel="next" href="asterisk-CHP-13-SECT-7.html" title="Conclusion" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Music on Hold</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="asterisk-CHP-13-SECT-5.html">Prev</a> </td><th width="60%" align="center">Chapter 13. Managing Your Asterisk System</th><td width="20%" align="right"> <a accesskey="n" href="asterisk-CHP-13-SECT-7.html">Next</a></td></tr></table><hr /></div><div class="sect1" lang="en" xml:lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="asterisk-CHP-13-SECT-6"></a>Music on Hold</h2></div></div></div><p>Any popular <a id="ch12_musiconhold" class="indexterm"></a>PBX system offers the ability to supply a source of music to
be played for callers while on hold. Asterisk allows for a lot of
creativity in this regard.</p><p>Nowadays, everyone is familiar with the<a id="I_indexterm13_tt1662" class="indexterm"></a> MP3 music format, and there is a lot of interest in using
MP3s as a music-on-hold source. The concept sure seems like a good idea,
but there are a few things that we think should be given some
consideration:</p><div class="itemizedlist"><ul type="disc"><li><p>MP3 files are extremely complex, and require a substantial
amount of CPU to decode. If you have a lot of channels pulling music
from the system (for example, people sometimes like to listen to music
through their phone, or a call center may have several callers on
hold), the load on the CPU caused by all of the transcoding of the
stored MP3 files could place too much demand on a machine that is
otherwise suitable to the performance needs of the system.</p></li><li><p>Current-generation hard drives hold a lot of data, so there may
not be any reason to worry about cutting down hard drive use.
Compressed audio makes sense from a distribution standpoint (an MP3 is
a much smaller download than the equivalent in .wav format), but once
on your system, do we really care how much space they take up?</p></li><li><p>MP3 files don’t usually come with the right sort of licensing.
;-)</p></li></ul></div><p>Taking all of this into consideration, we recommend that you convert
your music sources into the native format of the various codecs you may be
supporting. For example, if you support μlaw for your internal phones, and
G.729 on your VoIP circuits, you will want to store your music in both
formats so that Asterisk will not have to perform transcoding to play
music to calls on those channels.</p><div class="sidebar"><a id="I_sidebar13_tt1663"></a><p class="title"><b>Free Music</b></p><p>A lot of people do not realize that playing music on hold requires
a special license.<a id="I_indexterm13_tt1664" class="indexterm"></a> This is true even if you play music from CDs that you
own, or from the radio. To ensure that there is no ambiguity, we
recommend avoiding the whole matter and using only music that does not
come encumbered with the kind of licenses that the music industry seems
to prefer.</p><p>There are many web sites where you can go to get music that is
licensed in a manner that is suitable for music on hold. Two that we
have found are <a href="http://en.wikipedia.org/wiki/Wikipedia:Sound/list" target="_top">http://en.wikipedia.org/wiki/Wikipedia:Sound/list</a> and
<a href="http://www.opsound.org/" target="_top">http://www.opsound.org/</a>.</p><p>Both offer a sizeable collection of music that can be easily
downloaded. Note that this may not all be of professional quality, so
listen to all of it before you commit it to your music-on-hold
collection.<sup>[<a id="id4159252" href="#ftn.id4159252">145</a>]</sup></p></div><p>We often use public domain music<a id="I_indexterm13_tt1665" class="indexterm"></a> (or <a id="I_indexterm13_tt1666" class="indexterm"></a>Creative Commons licensed music) on our systems. Creative
Commons music often comes in ogg-Vorbis format <a id="I_indexterm13_tt1667" class="indexterm"></a>(which is conceptually similar to MP3, but not compatible).
In order to play <span class="emphasis"><em>.ogg</em></span> or <span class="emphasis"><em>.mp3</em></span>
files on our Asterisk system, we are going to convert them to a format
that Asterisk can easily handle. This requires the following steps:</p><div class="orderedlist"><ol type="1"><li><p>We need to make sure that SoX, the <a id="I_indexterm13_tt1668" class="indexterm"></a>Sound eXchange utility, is installed. If not, run the
following command to install it:</p><a id="I_programlisting13_tt1669"></a><pre class="programlisting">$ <strong class="userinput"><code>yum install sox</code></strong></pre></li><li><p>Download the music that you have chosen to a working folder on
your system (<code class="filename">/tmp</code> is probably a suitable location).
As an example, the following command downloaded some nice piano music
by Pachelbel for us:</p><a id="I_programlisting13_tt1670"></a><pre class="programlisting">$ <strong class="userinput"><code>wget http://upload.wikimedia.org/wikipedia/commons/6/62/Pachelbel%27s_Canon.ogg</code></strong></pre></li><li><p>Now we have to convert the song from ogg-Vorbis format to a
format more suitable to Asterisk:</p><a id="I_programlisting13_tt1671"></a><pre class="programlisting">$ <strong class="userinput"><code>sox Pachelbel\'s_Canon.ogg -r 8000 -c 1 -s -w moh1.wav resample -ql</code></strong></pre><div class="tip" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Tip</h3><p>You may also need to adjust the amplitude with the <code class="literal">-v</code> option.</p></div><p>We’ve now taken our source file, converted it to a .wav file
suitable to Asterisk,<sup>[<a id="id4159410" href="#ftn.id4159410">146</a>]</sup> and saved the resulting file as
<span class="emphasis"><em>moh1.wav</em></span>.</p></li><li><p>Almost done now. We just need to create a folder for the
permanent home of the new files (<code class="filename">/tmp</code> is certainly no place for
them):</p><a id="I_programlisting13_tt1672"></a><pre class="programlisting">$ <strong class="userinput"><code>mkdir /var/lib/asterisk/mohwav</code></strong></pre><p>and then move them there:</p><a id="I_programlisting13_tt1673"></a><pre class="programlisting">$ <strong class="userinput"><code>mv *.wav /var/lib/asterisk/mohwav</code></strong></pre></li><li><p>Since we have placed our music files in a different folder from
that where Asterisk installs its sample music, we will need to change
the configuration file to reflect this. Edit your <code class="filename">/etc/asterisk/musiconhold.conf</code> file with
one that contains the <span class="keep-together">following</span>:</p><a id="I_programlisting13_tt1674"></a><pre class="programlisting">[default]
mode=files
directory=/var/lib/asterisk/mohwav
random=yes</pre></li></ol></div><p>As for what to play, that will depend on what image you want to
project to your callers. Regardless of your choice, you should keep some
things in mind:</p><div class="itemizedlist"><ul type="disc"><li><p>People don’t actually want to be on hold, so they are not
usually planning to be there for long. This means that there is not
much point in providing them with a mind-expanding musical experience.
If things go as they hope, they won’t be there long enough to get into
it.</p></li><li><p>The fidelity on a phone system does not allow for accurate
reproduction of tones. Heavy bass generally sounds terrible, and high
frequencies will typically just end up as noise. Keep the music
simple, and it is more likely to sound good.</p></li><li><p>Musical tastes are as varied as people, and while it might be
nice to try and cover a wide range of styles, music that is too
eclectic is more likely to annoy than enlighten.</p></li></ul></div><p>Classical music addresses all of the above criteria, and it is easy
to obtain. It also sounds classy (go figure!), so it is a pretty safe
choice, although we’ll admit it doesn’t usually score any points in the
hipness department.</p><p>Asterisk includes three songs with the source code download that are
licensed for use with Asterisk. These songs are intended as samples. Since
there are only three of them, people who call you regularly will quickly
tire of them. We have a recurring nightmare in which the worldwide success
of Asterisk means that the human race is forced to listen to the same
three songs as music on hold.<a id="I_indexterm13_tt1675" class="indexterm"></a> That is why we wrote this section
for you.</p><div class="sidebar"><a id="I_sidebar13_tt1676"></a><p class="title"><b>Randomizing Music on Hold</b></p><p>In a traditional PBX, music on hold usually comes from a single
source. Everyone that is hearing music is hearing the exact same thing
at the exact same time, and even when no one is on hold, the music is
still playing. On Asterisk, the music is not playing until a need for it
arises, and each caller gets her own music source. If Asterisk were to
simply start playing songs in the order it found them, each call placed
on hold would always hear the same song starting from the beginning. In
order to simulate traditional music on hold, Asterisk can (and normally
should) be set to play the music in a random fashion. This means that it
will select which file to play at random. If you have enough different
songs in your music-on-hold directory, you will minimize the chance that
someone who calls frequently will have to listen to the same songs all
of the time.</p></div><div class="footnotes"><br /><hr width="100" align="left" /><div class="footnote"><p><sup>[<a id="ftn.id4159252" href="#id4159252">145</a>] </sup>Seed a search with the term “Creative Commons music” to find
more freely usable music.</p></div><div class="footnote"><p><sup>[<a id="ftn.id4159410" href="#id4159410">146</a>] </sup>Note that we could have used any format that was compatible
with Asterisk; we’ve just chosen .wav for this example because it
is easy for the CPU to transcode into μlaw/alaw/slin on the fly,
yet remains easy to work with in other environments.</p></div></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="asterisk-CHP-13-SECT-5.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="asterisk-CHP-13.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="asterisk-CHP-13-SECT-7.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Customizing System Prompts </td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top"> Conclusion</td></tr></table></div><div xmlns="" id="svn-footer"><hr /><p>You are reading <em>Asterisk: The Future of Telephony</em> (2nd Edition for Asterisk 1.4), by Jim van Meggelen, Jared Smith, and Leif Madsen.<br />
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