Based on kernel version 4.0. Page generated on 2015-04-14 21:23 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>