1<html><head><meta http-equiv="Content-Type" content="text/html; charset=ANSI_X3.4-1968"><title>Teletext Interface</title><meta name="generator" content="DocBook XSL Stylesheets V1.78.1"><link rel="home" href="index.html" title="LINUX MEDIA INFRASTRUCTURE API"><link rel="up" href="devices.html" title="Chapter 4. Interfaces"><link rel="prev" href="sliced.html" title="Sliced VBI Data Interface"><link rel="next" href="radio.html" title="Radio Interface"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Teletext Interface</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="sliced.html">Prev</a> </td><th width="60%" align="center">Chapter 4. Interfaces</th><td width="20%" align="right"> <a accesskey="n" href="radio.html">Next</a></td></tr></table><hr></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="ttx"></a>Teletext Interface</h2></div></div></div><p>This interface was aimed at devices receiving and demodulating 2Teletext data [<a class="xref" href="bi01.html#ets300706" title='ETS 300 706 "Enhanced Teletext specification"'>[<abbr class="abbrev">ETS 300 706</abbr>]</a>, <a class="xref" href="bi01.html#itu653" title='ITU-R Recommendation BT.653-3 "Teletext systems"'>[<abbr class="abbrev">ITU BT.653</abbr>]</a>], evaluating the 3Teletext packages and storing formatted pages in cache memory. Such 4devices are usually implemented as microcontrollers with serial 5interface (I<sup>2</sup>C) and could be found on old 6TV cards, dedicated Teletext decoding cards and home-brew devices 7connected to the PC parallel port.</p><p>The Teletext API was designed by Martin Buck. It was defined in 8the kernel header file <code class="filename">linux/videotext.h</code>, the 9specification is available from <a class="ulink" href="ftp://ftp.gwdg.de/pub/linux/misc/videotext/" target="_top"> 10ftp://ftp.gwdg.de/pub/linux/misc/videotext/</a>. (Videotext is the name of 11the German public television Teletext service.)</p><p>Eventually the Teletext API was integrated into the V4L API 12with character device file names <code class="filename">/dev/vtx0</code> to 13<code class="filename">/dev/vtx31</code>, device major number 81, minor numbers 14192 to 223.</p><p>However, teletext decoders were quickly replaced by more 15generic VBI demodulators and those dedicated teletext decoders no longer exist. 16For many years the vtx devices were still around, even though nobody used 17them. So the decision was made to finally remove support for the Teletext API in 18kernel 2.6.37.</p><p>Modern devices all use the <a class="link" href="raw-vbi.html" title="Raw VBI Data Interface">raw</a> or 19<a class="link" href="sliced.html" title="Sliced VBI Data Interface">sliced</a> VBI API.</p></div><div class="navfooter"><hr><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="sliced.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="devices.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="radio.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Sliced VBI Data Interface </td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top"> Radio Interface</td></tr></table></div></body></html> 20