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<TITLE>Installing and using MythTV: Configuring Sound.</TITLE>
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<H2><A NAME="s7">7.</A> <A HREF="mythtv-HOWTO.html#toc7">Configuring Sound.</A></H2>
<P>If your video doesn't appear to be in-sync with your audio and you're
using an analog video capture card and a soundcard to capture audio, it
could be because you are listening to the real-time audio from your video
card rather than after it's been processed and synchronized to the video by
MythTV. Because MythTV is a personal video recorder, "Live TV" isn't really
live - to let you pause live TV, MythTV is actually encoding the video,
saving to disk, and then playing it back. This procedure puts your MythTV
"live" TV about 2 seconds behind real-time, so it's important that you're
not listening to the live audio. However, if you're having an issue where
the audio and video aren't synchronized by small but varying amount, it's
most likely because the sound driver that you're using doesn't have the
DSP_CAP_REALTIME capability. This was the case with ALSA (0.5), but not
with newer versions. See the
<A HREF="mythtv-HOWTO-22.html#Troubleshooting_Audio">Troubleshooting Audio</A> section for more information if you're having
issues with sound. Also, ensure that no other programs are grabbing the
audio output, like <B>arts</B> or <B>esd</B>.</P>
<P>What you need to do is to mute the "line-in" of your sound card and also
set it as the recording source.</P>
<P>There are two ways to do this. Graphically, and from the command line.</P>
<H2><A NAME="ss7.1">7.1</A> <A HREF="mythtv-HOWTO.html#toc7.1">Graphically setting up the mixer</A>
</H2>
<H3>Mandriva and Red Hat Linux/Fedora Core</H3>
<P>Open Kmix by clicking K->Multimedia->Sound->Kmix for Mandriva, or
<PRE>
RedHat Menu>Sound & Video>Volume Control
</PRE>
on Red Hat/Fedora.</P>
<P>Click on Settings->Configure Make sure that "Tick Marks" and "Show
labels" have "X"'s in them. This will make it easier to find the correct
audio source. Click OK.</P>
<P>On the mixer page, look for Line-In on your sound card. You should see
two LED's - a green one at the top, and a red one at the bottom. The green
one at the top is for muting; you want to make sure that the green LED is a
dark green, meaning that it's "off". You also want to click on the red LED
so that it turns bright red, indicating that it's "ON"; this insures that
the Line-in is used as the source. Click OK, and make sure that you save
the settings so that this is your default.</P>
<H3>Using ALSA.</H3>
<P>To use ALSA, you'll need to correctly setup your
<CODE>asoundrc</CODE> file. Configuring this file is beyond the scope of this
HOWTO. Once ALSA is working correctly, change the output sound device in
mythfrontend->setup->Audio from <CODE>/dev/dsp</CODE> to <CODE>ALSA:default</CODE>.
This field may be edited to suit your ALSA requirements.</P>
<H2><A NAME="ss7.2">7.2</A> <A HREF="mythtv-HOWTO.html#toc7.2">Setting the mixer from the command line</A>
</H2>
<P>If you have installed the alsa-utils package, then the <B>amixer</B>
program can be used to setup the mixer. The "Master" volume setting is only
required on a frontend machine to ensure that the sound channels are unmuted
and configured for outputting sound. The "Line" and "Capture" controls are
required for your sound card to actually capture audio from the external
Line-in if it's connected to an analog frame grabber. Not all sound cards
have a "Capture" control, but if yours does and you don't set it then MythTV
will not capture audio.</P>
<P>
<HR>
<PRE>
Note the spelling in the following commands.
</PRE>
<HR>
<BLOCKQUOTE><CODE>
<PRE>
$ amixer set Master,0 100%,100% unmute
$ amixer set PCM,0 100%,100% unmute
$ amixer set Line,0 75%,75% mute captur
$ amixer set Capture,0 100%,100% captur
$ su
# alsactl store
# exit
$
</PRE>
</CODE></BLOCKQUOTE>
</P>
<P>If you have multiple sound cards, then use the <CODE>-c</CODE> parameter to
specify which card to adjust. Note that the first card will be "0", the
second will be "1", etc.</P>
<P>That takes care of setting the volume correctly, and the ALSA startup script
will restore the volume after a reboot. If you find that your sound is
distorted, it's possible that the levels in the above examples are too high
for your particular hardware combination. Try reducing the percentages by
5-10% and checking again. Once you're satisfied, re-run the <CODE>alsactl
store</CODE> command.</P>
<P>You may also use the <B>alsamixer</B> program to set the volume. If you
are using an ALSA version after 1.0.6, use <B>alsamixer -V all</B> First,
start <B>alsamixer</B> from the command line. You should start out on the
"Master" volume control slider. Use the up and down cursor to set the
master volume to around 75%. Next, use the left and right cursor keys to
move around on the screen until you find the "Line" slider. Press SPACE to
set it as the capture source, set the level to around 50-75% and press "M"
to mute it. You can now press ESC to exit out of the <B>alsamixer</B>
program. You can also have MythTV manage all volume and mute settings, but
this will only affect the "Master" or PCM volume, not the capture volume. See
the mythfrontend setup page for options.</P>
<P>Finally, if you've performed all of the above steps, and you still don't seem to have any sound, it's possible that your video capture device is muting the audio output.
<BLOCKQUOTE><CODE>
<PRE>
$ v4lctl -c /dev/video0 setattr mute off
</PRE>
</CODE></BLOCKQUOTE>
</P>
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