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Based on kernel version 3.16. Page generated on 2014-08-06 21:38 EST.

1	  <title>Teletext Interface</title>
2	
3	  <para>This interface was aimed at devices receiving and demodulating
4	Teletext data [<xref linkend="ets300706" />, <xref linkend="itu653" />], evaluating the
5	Teletext packages and storing formatted pages in cache memory. Such
6	devices are usually implemented as microcontrollers with serial
7	interface (I<superscript>2</superscript>C) and could be found on old
8	TV cards, dedicated Teletext decoding cards and home-brew devices
9	connected to the PC parallel port.</para>
10	
11	  <para>The Teletext API was designed by Martin Buck. It was defined in
12	the kernel header file <filename>linux/videotext.h</filename>, the
13	specification is available from <ulink url="ftp://ftp.gwdg.de/pub/linux/misc/videotext/">
14	ftp://ftp.gwdg.de/pub/linux/misc/videotext/</ulink>. (Videotext is the name of
15	the German public television Teletext service.)</para>
16	
17	  <para>Eventually the Teletext API was integrated into the V4L API
18	with character device file names <filename>/dev/vtx0</filename> to
19	<filename>/dev/vtx31</filename>, device major number 81, minor numbers
20	192 to 223.</para>
21	
22	  <para>However, teletext decoders were quickly replaced by more
23	generic VBI demodulators and those dedicated teletext decoders no longer exist.
24	For many years the vtx devices were still around, even though nobody used
25	them. So the decision was made to finally remove support for the Teletext API in
26	kernel 2.6.37.</para>
27	
28	  <para>Modern devices all use the <link linkend="raw-vbi">raw</link> or
29	<link linkend="sliced">sliced</link> VBI API.</para>
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