mirror of https://github.com/mpv-player/mpv
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292 lines
12 KiB
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<P><B><A NAME=2.3.2>2.3.2. Audio output devices</A></B></P>
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<P><B>MPlayer</B>'s audio interface is called <I>libao2</I>. It currently
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contains these drivers:</P>
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<TABLE BORDER=0>
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<TR><TD COLSPAN=4><P><B>General:</B></P></TD></TR>
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<TR><TD> </TD><TD VALIGN=top>oss</TD><TD> </TD><TD>OSS (ioctl) driver (supports hardware AC3 passthrough)</TD></TR>
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<TR><TD></TD><TD VALIGN=top>sdl</TD><TD></TD><TD>SDL driver (supports up/downsampling, <B>ESD</B>, <B>ARTS</B> etc)</TD></TR>
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<TR><TD></TD><TD VALIGN=top>nas</TD><TD></TD><TD>NAS (Network Audio System) driver</TD></TR>
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<TR><TD></TD><TD VALIGN=top>alsa5</TD><TD></TD><TD>native ALSA 0.5 driver</TD></TR>
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<TR><TD></TD><TD VALIGN=top>alsa9</TD><TD></TD><TD>native ALSA 0.9 driver (supports hardware AC3 passthrough)</TD></TR>
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<TR><TD></TD><TD VALIGN=top>sun</TD><TD></TD><TD>SUN audio driver (<CODE>/dev/audio</CODE>) for BSD and Solaris8 users</TD></TR>
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<TR><TD></TD><TD VALIGN=top>arts</TD><TD></TD><TD>native ARTS driver (mostly for KDE users)</TD></TR>
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</TABLE>
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<P>Fact is, Linux sound card drivers have compatibility problems.
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It <B>may</B> take a while to find your optimal settings.</P>
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<UL>
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<LI>If you have an OSS driver, first try <CODE>-ao oss</CODE> (this is the default).
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If you experience glitches, halts or anything out of the ordinary, try
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<CODE>-ao sdl</CODE> (NOTE: you need to have SDL libraries and header files
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installed). The SDL audio driver helps in a lot of cases and also supports ESD,
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ARTS, and up/downsampling. (ESD is the sound daemon from GNOME, ARTS is from KDE.)</LI>
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<LI>If you have ALSA version 0.5, then you almost always have to use <CODE>-ao alsa5</CODE> ,
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since ALSA 0.5 has buggy OSS emulation code, and will <B>crash MPlayer</B> with
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a message like this:<BR>
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<CODE>DEMUXER: Too many (945 in 8390980 bytes) video packets in the buffer!</CODE></LI>
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<LI>If you have ALSA version 0.9 you may choose between <CODE>-ao oss</CODE> and
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<CODE>-ao sdl</CODE>. You can also use <CODE>-ao alsa9</CODE>. It works, but
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there may be problems like lost sync and disappearing audio.</LI>
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</UL>
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<P>On <B>Solaris/FreeBSD</B> systems, use the SUN audio driver with the
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<CODE>-ao sun</CODE> option, otherwise neither video nor audio will work.</P>
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<P><B><A NAME=2.3.2.1>2.3.2.1. Sound Card experiences, recommendations</A></B></P>
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<TABLE BORDER=0 WIDTH="100%">
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<TR><TD COLSPAN=3><B>VIA onboard chipset (via82cxxx) 48kHz only</B></TD><TR>
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<TD></TD><TD>Driver:</TD><TD> from <A HREF="http://sourceforge.net/project/showfiles.php?group_id=3242&release_id=59602">here</A></TD><TR>
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<TD COLSPAN=3><B>Aureal Vortex 2</B></TD><TR>
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<TD> </TD><TD>OSS:</TD><TD>no driver</TD><TR>
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<TD></TD><TD>OSS/Pro:</TD><TD>OK</TD><TR>
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<TD></TD><TD>ALSA:</TD><TD>no driver</TD><TR>
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<TD></TD><TD>Max kHz:</TD><TD>48</TD><TR>
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<TD></TD><TD>Driver:</TD><TD><A HREF="http://aureal.sourceforge.net">aureal.sourceforge.net</A></TD><TR>
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<TD></TD><TD>Driver2:</TD><TD> from <A HREF="http://makacs.poliod.hu/~pontscho/aureal/au88xx-1.1.3.tar.bz2">here</A><BR>
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(<I>buffer size increased to 32k</I>)</TD><TR>
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<TD COLSPAN=3><B>GUS PnP</B></TD><TR>
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<TD></TD><TD>OSS:</TD><TD>no driver</TD><TR>
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<TD></TD><TD>OSS/Pro:</TD><TD>OK</TD><TR>
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<TD></TD><TD>ALSA:</TD><TD>OK</TD><TR>
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<TD></TD><TD>Max kHz:</TD><TD>48</TD><TR>
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<TD COLSPAN=3><B>SB Live!</B></TD><TR>
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<TD></TD><TD>OSS:</TD><TD>Analog OK, SP/DIF not working</TD><TR>
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<TD></TD><TD>ALSA:</TD><TD>Both OK</TD><TR>
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<TD></TD><TD>Max kHz:</TD><TD>192</TD><TR>
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<TD COLSPAN=3><B>SB AWE 64</B></TD><TR>
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<TD></TD><TD>OSS:</TD><TD>max 44kHz</TD><TR>
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<TD></TD><TD>ALSA:</TD><TD>48kHz sounds bad</TD><TR>
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<TD></TD><TD>Max kHz:</TD><TD>48</TD><TR>
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<TD COLSPAN=3><B>Gravis UltraSound ACE</B></TD><TR>
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<TD></TD><TD>OSS:</TD><TD>not OK</TD><TR>
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<TD></TD><TD>ALSA:</TD><TD>OK</TD><TR>
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<TD></TD><TD>Max kHz:</TD><TD>44</TD><TR>
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<TD COLSPAN=3><B>Gravis UltraSound MAX</B></TD><TR>
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<TD></TD><TD>OSS:</TD><TD>OK</TD><TR>
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<TD></TD><TD>ALSA:</TD><TD>OK (?)</TD><TR>
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<TD></TD><TD>Max kHz:</TD><TD>48</TD><TR>
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<TD COLSPAN=3><B>ESS 688</B></TD><TR>
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<TD></TD><TD>OSS:</TD><TD>OK</TD><TR>
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<TD></TD><TD>ALSA:</TD><TD>OK (?)</TD><TR>
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<TD></TD><TD>Max kHz:</TD><TD>48</TD><TR>
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<TD COLSPAN=3><B>C-Media cards (which ones?)</B></TD><TR>
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<TD></TD><TD>OSS:</TD><TD>not OK (hissing) (?)</TD><TR>
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<TD></TD><TD>ALSA:</TD><TD>OK (?)</TD><TR>
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<TD></TD><TD>Max kHz:</TD><TD>?</TD><TR>
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<TD COLSPAN=3><B>Yamaha cards (*ymf*)</B></TD><TR>
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<TD></TD><TD>OSS:</TD><TD>not OK (?) (maybe <CODE>-ao sdl</CODE>)</TD><TR>
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<TD></TD><TD>ALSA:</TD><TD>OK only with ALSA 0.5 with OSS emulation <B>AND</B> <CODE>-ao sdl</CODE> (!) (?)</TD><TR>
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<TD></TD><TD>Max kHz:</TD><TD>?</TD><TR>
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<TD COLSPAN=3><B>Cards with envy24 chips (like Terratec EWS88MT)</B></TD><TR>
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<TD></TD><TD>OSS:</TD><TD>?</TD><TR>
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<TD></TD><TD>OSS/Pro:</TD><TD>OK</TD><TR>
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<TD></TD><TD>ALSA:</TD><TD>?</TD><TR>
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<TD></TD><TD>Max kHz:</TD><TD>?</TD><TR>
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<TD COLSPAN=3><B>PC Speaker or DAC</B></TD><TR>
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<TD></TD><TD>OSS:</TD><TD>OK (Use the SDL driver: <CODE>-ao sdl</CODE>)</TD><TR>
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<TD></TD><TD>ALSA:</TD><TD>no driver</TD><TR>
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<TD></TD><TD>Max kHz:</TD><TD>The driver emulates 44.1, maybe more.</TD><TR>
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<TD></TD><TD>Driver:</TD><TD><A HREF="ftp://ftp.infradead.org/pub/pcsp">ftp://ftp.infradead.org/pub/pcsp</A></TD>
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</TABLE>
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<UL>
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<LI>On Linux, a 2.4.x kernel is highly recommended. Kernel 2.2 is not tested.</LI>
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<LI>If sound clicks when playing from CD-ROM, turn on IRQ unmasking, e.g.
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<CODE>hdparm -u1 /dev/cdrom</CODE> (<CODE>man hdparm</CODE>). This is
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generally beneficial and described more detailed in the
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<A HREF="cd-dvd.html#4.1">CD-ROM section</A>.</LI>
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<LI>Sharing your sound card with another application like XMMS is <B>strongly discouraged</B>!
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If the other sound application is using ESD, start <B>MPlayer</B> with the <CODE>-vo sdl:esd</CODE> option
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to combine both sound streams! In fact, the option <CODE>-vo sdl:esd</CODE> could be used with ESD
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even when playing <B>Mplayer</B> alone.</LI>
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<LI>Feedback to this document is welcome. Please tell us how <B>MPlayer</B> and
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your sound card(s) worked together.</LI>
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</UL>
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<P><B><A NAME=2.3.2.2>2.3.2.2. Audio plugins</A></B></P>
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<P><B>MPlayer</B> has support for audio plugins. Audio plugins can be used for
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changing the properties of the audio data before the sound reaches the sound
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card. They are enabled using the <CODE>-aop</CODE> switch which takes a
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<CODE>list=plugin1,plugin2,...</CODE> argument. The <CODE>list</CODE> argument
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is required and determines which plugins should be used and in which order they
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should be executed. Example:
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</P>
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<P> <CODE>mplayer media.avi -aop list=resample,format</CODE></P>
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<P>would run the sound through the resampling plugin followed by the format
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plugin.
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</P>
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<P>The plugins can also have switches that change their behavior. These
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switches are explained in detail in the sections below. A plugin will execute
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using default settings if its switches are omitted. Here is an example of how
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to use plugins in combination with plugin specific switches:
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</P>
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<P> <CODE>mplayer media.avi -aop
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list=resample,format:fout=44100:format=0x8</CODE>
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</P>
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<P>would set the output frequency of the resample plugin to 44100Hz and the
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output format of the format plugin to AFMT_U8.
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</P>
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<P>Currently audio plugins can not be used in <B>MEncoder</B>.</P>
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<P><B><A NAME=2.3.2.2.1>2.3.2.2.1. Up/Downsampling</A></B></P>
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<P><B>MPlayer</B> fully supports up/downsampling of the sound. This plugin can
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be used if you have a fixed frequency sound card or if you are
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stuck with an old sound card that is only capable of max 44.1kHz.
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Limitations in your hardware are not auto detected, so you have to specify
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the sample frequency explicitly. This plugin has one switch:
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<CODE>fout</CODE> which is used for setting the desired output sample
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frequency. It defaults to 48kHz, and is given in
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<Hz>.
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</P>
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<P>Usage:<BR>
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<CODE>mplayer media.avi -aop list=resample:fout=<required
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frequency in Hz, like 44100></CODE></P>
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<P>Note that the output frequency should not be scaled up from the default value.
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Scaling up will cause the audio and video streams to be played in slow motion
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in addition to audio distortion.</P>
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<P><B><A NAME=2.3.2.2.2>2.3.2.2.2. Surround Sound decoding</A></B></P>
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<P><B>MPlayer</B> has an audio plugin that can decode matrix encoded
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surround sound. Dolby Surround is an example of a matrix encoded format.
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Many files with 2 channel audio actually contain matrixed surround sound.
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To use this feature you need a sound card supporting at least 4 channels.</P>
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<P>Usage:<BR>
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<CODE>mplayer media.avi -aop list=surround</CODE></P>
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<P><B><A NAME=2.3.2.2.3>2.3.2.2.3. Sample format converter</A></B></P>
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<P>If your sound card driver does not support signed 16bit <CODE>int</CODE> data type,
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this plugin can
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be used to change the format to one which your sound card can understand. It
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has one switch, <CODE>format</CODE>, which can be set to one of the numbers
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found in <CODE>libao2/afmt.h</CODE>. This plugin is hardly ever needed and is
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intended for advanced users. Keep in mind that this plugin only changes the
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sample format and not the sample frequency or the number of channels.
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</P>
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<P>Usage:<BR>
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<CODE>mplayer media.avi -aop
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list=format:format=<required output format></CODE>
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</P>
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<P><B><A NAME=2.3.2.2.4>2.3.2.2.4. Delay</A></B></P>
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<P>This plugin delays the sound and is intended as an example of how to develop
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new plugins. It can not be used for anything useful from a users perspective
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and is mentioned here for the sake of completeness only. Do not use this
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plugin unless you are a developer.</P>
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<P><B><A NAME=2.3.2.2.5>2.3.2.2.5. Software volume control</A></B></P>
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<P>This plugin is a software replacement for the volume control, and
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can be used on machines with a broken mixer device. It can also be
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used if one wants to change the output volume of <B>MPlayer</B>
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without changing the PCM volume setting in the mixer. It has one
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switch <CODE>volume</CODE> that is used for setting the initial
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sound level. The initial sound level can be set to values between 0
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and 255 and defaults to 101 which equals 0dB amplification. Use this
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plugin with caution since it can reduce the signal to noise ratio of
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the sound. In most cases it is best to set the level for the PCM
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sound to max, leave this plugin out and control the output level to
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your speakers with the master volume control of the mixer. If there is an
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external amplifier connected to the computer (this is almost always
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the case), the noise level can be minimized by adjusting the master
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level and the volume knob on the amplifier until the hissing noise
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in the background is gone.
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</P>
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<P>Usage:<BR>
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<CODE>mplayer media.avi -aop
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list=volume:volume=<0-255></CODE>
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</P>
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<P>This plugin also has compressor or "soft-clipping" capabilities.
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Compression can be used if the dynamic range of the sound is very
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high or if the dynamic range of the loudspeakers is very
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low. Be aware that this feature creates distortion and should be
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considered a last resort.
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</P>
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<P>Usage:<BR>
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<CODE>mplayer media.avi -aop
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list=volume:softclip</CODE>
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</P>
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<P><B><A NAME=2.3.2.2.6>2.3.2.2.6. Extrastereo</A></B></P>
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<P>This plugin (linearly) increases the difference between left and right
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channels (like the XMMS extrastereo plugin) which gives some sort of "live"
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effect to playback.
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</P>
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<P>Usage:<BR>
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<CODE>mplayer media.avi -aop list=extrastereo</CODE><BR>
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<CODE>mplayer media.avi -aop list=extrastereo:mul=3.45</CODE></P>
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<P>The default coefficient (<CODE>mul</CODE>) is a float number that defaults
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to 2.5. If you set it to 0.0, you will have mono sound (average of both
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channels). If you set it to 1.0, sound will be unchanged, if you set it to
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-1.0, left and right channels will be swapped.</P>
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<P><B><A NAME=2.3.2.2.7>2.3.2.2.7. Volume normalizer</A></B></P>
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<P>This plugin maximizes the volume without distorting the sound.</P>
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<P>Usage:<BR>
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<CODE>mplayer media.avi -aop list=volnorm</CODE><BR>
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<P><B><A NAME=2.3.2.2.8>2.3.2.2.8. Surround</A></B></P>
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<P>Someone should document something, sometime.</P>
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