mpv/DOCS/xml/en/audio.xml

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<chapter id="audio">
<title>Audio output devices</title>
<sect1 id="sync">
<title>Audio/Video synchronization</title>

<para>
Linux sound card drivers have compatibility problems. This is because
<application>MPlayer</application> relies on an in-built feature of
<emphasis>properly</emphasis> coded sound drivers that enable them to
maintain correct audio/video sync. Regrettably, some driver authors
don't take the care to code this feature since it is not needed for
playing MP3s or sound effects.
</para>

<para>
Other media players like <ulink url="http://avifile.sf.net">aviplay</ulink>
or <ulink url="http://xinehq.de">xine</ulink> possibly work
out-of-the-box with these drivers because they use "simple" methods
with internal timing. Measuring showed that their methods are not as
efficient as <application>MPlayer</application>'s.
</para>

<para>
Using <application>MPlayer</application> with a properly written audio
driver will never result in A/V desyncs related to the audio, except
only with very badly created files (check the man page for workarounds).
</para>

<para>
If you happen to have a bad audio driver, try the <option>-autosync</option>
option, it should sort out your problems. See the man page for detailed
information.
</para>
</sect1>

<sect1 id="troubleshooting">
<title>Troubleshooting</title>

<para>Some notes:</para>

<para>
  If you have ALSA version 0.5, then you almost always have to use
  <option>-ao alsa5</option>, since ALSA 0.5 has buggy OSS emulation code,
  and will <emphasis role="bold">crash <application>MPlayer</application></emphasis>
  with a message like this:
  <screen>
DEMUXER: Too many (945 in 8390980 bytes) video packets in the buffer!<!--
--></screen>
</para>
<para>
  If the sound clicks when playing from CD-ROM, turn on IRQ unmasking as
  described in the <link linkend="drives">CD-ROM</link> section.
</para>
</sect1>

</chapter>