mirror of https://github.com/mpv-player/mpv
280 lines
10 KiB
XML
280 lines
10 KiB
XML
<?xml version="1.0" encoding="utf-8"?>
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<!-- $Revision$ -->
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<chapter id="tv">
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<title>TV</title>
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<sect1 id="tv-input" xreflabel="TV input">
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<title>TV input</title>
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<para>
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This section is about how to enable <emphasis role="bold">watching/grabbing
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from V4L compatible TV tuner</emphasis>. See the man page for a description
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of TV options and keyboard controls.
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</para>
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<!-- ********** -->
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<sect2 id="tv-compilation">
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<title>Compilation</title>
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<procedure>
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<step><para>
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First, you have to recompile. <filename>./configure</filename> will
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autodetect kernel headers of v4l stuff and the existence of
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<filename>/dev/video*</filename> entries. If they exist, TV support will
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be built (see the output of <filename>./configure</filename>).
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</para></step>
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<step><para>
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Make sure your tuner works with another TV software in Linux, for
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example <application>XawTV</application>.
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</para></step>
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</procedure>
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</sect2>
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<!-- ********** -->
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<sect2 id="tv-tips">
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<title>Usage tips</title>
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<para>
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The full listing of the options is available on the manual page.
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Here are just a few tips:
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<itemizedlist>
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<listitem><para>
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Use the <option>channels</option> option. An example:
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<screen>-tv channels=26-MTV1,23-TV2</screen>
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Explanation: Using this option, only the 26 and 23 channels will be usable,
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and there will be a nice OSD text upon channel switching, displaying the
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channel's name. Spaces in the channel name must be replaced by the
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"_" character.
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</para></listitem>
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<listitem><para>
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Choose some sane image dimensions. The dimensions of the resulting image
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should be divisible by 16.
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</para></listitem>
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<listitem>
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<para>
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If you capture the video with the vertical resolution higher than half
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of the full resolution (i.e. 288 for PAL or 240 for NTSC), then the
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'frames' you get will really be interleaved pairs of fields.
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Depending on what you want to do with the video you may leave it in
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this form, destructively deinterlace, or break the pairs apart into
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individual fields.
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</para>
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<para>
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Otherwise you'll get a movie which is distorted during
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fast-motion scenes and the bitrate controller will be probably even unable
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to retain the specified bitrate as the interlacing artifacts produce high
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amount of detail and thus consume lot of bandwidth. You can enable
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deinterlacing with <option>-vf pp=DEINT_TYPE</option>.
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Usually <option>pp=lb</option> does a good job, but it can be matter of
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personal preference.
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See other deinterlacing algorithms in the manual and give it a try.
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</para>
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</listitem>
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<listitem><para>
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Crop out the dead space. When you capture the video, the areas at the edges
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are usually black or contain some noise. These again consume lots of
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unnecessary bandwidth. More precisely it's not the black areas themselves
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but the sharp transitions between the black and the brighter video image
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which do but that's not important for now. Before you start capturing,
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adjust the arguments of the <option>crop</option> option so that all the
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crap at the margins is cropped out. Again, don't forget to keep the resulting
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dimensions sane.
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</para></listitem>
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<listitem><para>
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Watch out for CPU load. It shouldn't cross the 90% boundary for most of the
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time. If you have a large capture buffer, <application>MEncoder</application>
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can survive an overload for few seconds but nothing more. It's better to
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turn off the 3D OpenGL screensavers and similar stuff.
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</para></listitem>
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<listitem><para>
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Don't mess with the system clock. <application>MEncoder</application> uses the
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system clock for doing A/V sync. If you adjust the system clock (especially
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backwards in time), <application>MEncoder</application> gets confused and you
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will lose frames. This is an important issue if you are hooked to a network
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and run some time synchronization software like NTP. You have to turn NTP
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off during the capture process if you want to capture reliably.
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</para></listitem>
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<listitem><para>
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Don't change the <option>outfmt</option> unless you know what you are doing
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or your card/driver really doesn't support the default (YV12 colorspace).
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In the older versions of <application>MPlayer</application>/
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<application>MEncoder</application> it was necessary to specify the output
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format. This issue should be fixed in the current releases and
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<option>outfmt</option> isn't required anymore, and the default suits the
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most purposes. For example, if you are capturing into DivX using
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<systemitem class="library">libavcodec</systemitem> and specify
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<option>outfmt=RGB24</option> in order to increase the quality of the captured
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images, the captured image will be actually later converted back into YV12 so
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the only thing you achieve is a massive waste of CPU power.
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</para></listitem>
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<listitem><para>
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To specify the I420 colorspace (<option>outfmt=i420</option>), you have to
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add an option <option>-vc rawi420</option> due to a fourcc conflict with an
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Intel Indeo video codec.
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</para></listitem>
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<listitem><para>
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There are several ways of capturing audio. You can grab the sound either using
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your sound card via an external cable connection between video card and
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line-in, or using the built-in ADC in the bt878 chip. In the latter case, you
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have to load the <emphasis role="bold">btaudio</emphasis> driver. Read the
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<filename>linux/Documentation/sound/btaudio</filename> file (in the kernel
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tree, not <application>MPlayer</application>'s) for some instructions on using
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this driver.
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</para></listitem>
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<listitem><para>
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If <application>MEncoder</application> cannot open the audio device, make
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sure that it is really available. There can be some trouble with the sound
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servers like aRts (KDE) or ESD (GNOME). If you have a full duplex sound card
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(almost any decent card supports it today), and you are using KDE, try to
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check the "full duplex" option in the sound server preference menu.
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</para></listitem>
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</itemizedlist>
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</para>
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</sect2>
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<!-- ********** -->
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<sect2 id="tv-examples">
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<title>Examples</title>
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<informalexample><para>
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Dummy output, to AAlib :)
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<screen>mplayer -tv driver=dummy:width=640:height=480 -vo aa tv://</screen>
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</para></informalexample>
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<informalexample><para>
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Input from standard V4L:
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<screen>
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mplayer -tv driver=v4l:width=640:height=480:outfmt=i420 -vc rawi420 -vo xv tv://
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</screen>
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</para></informalexample>
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<informalexample><para>
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A more sophisticated example. This makes <application>MEncoder</application>
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capture the full PAL image, crop the margins, and deinterlace the picture
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using a linear blend algorithm. Audio is compressed with a constant bitrate
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of 64kbps, using LAME codec. This setup is suitable for capturing movies.
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<screen>
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mencoder -tv driver=v4l:width=768:height=576 -oac mp3lame -lameopts cbr:br=64\
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-ovc lavc -lavcopts vcodec=mpeg4:vbitrate=900 \
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-vf crop=720:544:24:16,pp=lb -o <replaceable>output.avi</replaceable> tv://
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</screen>
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</para></informalexample>
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<informalexample><para>
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This will additionally rescale the image to 384x288 and compresses the
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video with the bitrate of 350kbps in high quality mode. The vqmax option
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looses the quantizer and allows the video compressor to actually reach so
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low bitrate even at the expense of the quality. This can be used for
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capturing long TV series, where the video quality isn't so important.
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<screen>
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mencoder -tv driver=v4l:width=768:height=576 \
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-ovc lavc -lavcopts vcodec=mpeg4:vbitrate=350:vhq:vqmax=31:keyint=300 \
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-oac mp3lame -lameopts cbr:br=48 -sws 1 -o <replaceable>output.avi</replaceable>\
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-vf crop=720:540:24:18,pp=lb,scale=384:288 tv://
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</screen>
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It's also possible to specify smaller image dimensions in the
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<option>-tv</option> option and omit the software scaling but this approach
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uses the maximum available information and is a little more resistant to noise.
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The bt8x8 chips can do the pixel averaging only in the horizontal direction due
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to a hardware limitation.
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</para></informalexample>
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</sect2>
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</sect1>
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<!-- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -->
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<sect1 id="tv-teletext">
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<title>Teletext</title>
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<para>
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Teletext is currently available only in MPlayer for v4l and v4l2 drivers.
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</para>
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<sect2 id="tv-teletext-implementation-notes">
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<title>Implementation notes</title>
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<para>
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<application>MPlayer</application> supports regular text, graphics and navigation links.
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Unfortunately, colored pages are not fully supported yet - all pages are shown as grayscaled.
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Subtitle pages (also known as Closed Captions) are supported, too.
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</para>
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<para>
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<application>MPlayer</application> starts caching all teletext pages upon
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starting to receive TV input, so you do not need to wait until the requested page is loaded.
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</para>
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<para>
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Note: Using teletext with <option>-vo xv</option> causes strange colors.
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</para>
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</sect2>
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<sect2 id="tv-teletext-usage">
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<title>Using teletext</title>
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<para>
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To enable teletext decoding you must specify the VBI device to get teletext data
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from (usually <filename>/dev/vbi0</filename> for Linux). This can be done by specifying
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<option>tdevice</option> in your configuration file, like shown below:
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<screen>tv=tdevice=/dev/vbi0</screen>
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</para>
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<para>
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You might need to specify the teletext language code for your country.
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To list all available country codes use
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<screen>tv=tdevice=/dev/vbi0:tlang=<replaceable>-1</replaceable></screen>
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Here is an example for Russian:
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<screen>tv=tdevice=/dev/vbi0:tlang=<replaceable>33</replaceable></screen>
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</para>
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<para>
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</para>
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</sect2>
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<sect2 id="tv-teletext-hotkeys">
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<title>Teletext hot keys</title>
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<informaltable frame="all">
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<tgroup cols="2">
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<thead>
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<row>
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<entry>Key</entry>
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<entry>Description</entry>
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</row>
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</thead>
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<tbody>
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<row>
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<entry>X</entry>
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<entry>Switch teletext display on/off</entry>
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</row>
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<row>
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<entry>C</entry>
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<entry>Cycle through teletext rendering modes (opaque, transparent, inverted opaque,
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inverted transparent</entry>
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</row>
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<row>
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<entry>Left/Right</entry>
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<entry>Go to previous/next teletext page</entry>
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</row>
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<row>
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<entry>PageUp/PageDown</entry>
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<entry>Go to next/previous teletext subpage</entry>
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</row>
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<row>
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<entry>digits</entry>
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<entry>Enter teletext page number to jump to</entry>
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</row>
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</tbody>
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</tgroup>
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</informaltable>
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</sect2>
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</sect1>
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</chapter>
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