1 <title>Teletext Interface</title> 2 3 <para>This interface aims at devices receiving and demodulating 4Teletext data [<xref linkend="ets300706" />, <xref linkend="itu653" />], evaluating the 5Teletext packages and storing formatted pages in cache memory. Such 6devices are usually implemented as microcontrollers with serial 7interface (I<superscript>2</superscript>C) and can be found on older 8TV cards, dedicated Teletext decoding cards and home-brew devices 9connected to the PC parallel port.</para> 10 11 <para>The Teletext API was designed by Martin Buck. It is defined in 12the kernel header file <filename>linux/videotext.h</filename>, the 13specification is available from <ulink url="ftp://ftp.gwdg.de/pub/linux/misc/videotext/"> 14ftp://ftp.gwdg.de/pub/linux/misc/videotext/</ulink>. (Videotext is the name of 15the German public television Teletext service.) Conventional character 16device file names are <filename>/dev/vtx</filename> and 17<filename>/dev/vttuner</filename>, with device number 83, 0 and 83, 16 18respectively. A similar interface exists for the Philips SAA5249 19Teletext decoder [specification?] with character device file names 20<filename>/dev/tlkN</filename>, device number 102, N.</para> 21 22 <para>Eventually the Teletext API was integrated into the V4L API 23with character device file names <filename>/dev/vtx0</filename> to 24<filename>/dev/vtx31</filename>, device major number 81, minor numbers 25192 to 223. For reference the V4L Teletext API specification is 26reproduced here in full: "Teletext interfaces talk the existing VTX 27API." Teletext devices with major number 83 and 102 will be removed in 28Linux 2.6.</para> 29 30 <para>There are no plans to replace the Teletext API or to integrate 31it into V4L2. Please write to the linux-media mailing list: &v4l-ml; 32when the need arises.</para> 33 34 <!-- 35Local Variables: 36mode: sgml 37sgml-parent-document: "v4l2.sgml" 38indent-tabs-mode: nil 39End: 40 --> 41