mirror of https://gitee.com/openkylin/linux.git
41 lines
1.9 KiB
XML
41 lines
1.9 KiB
XML
<title>Teletext Interface</title>
|
|
|
|
<para>This interface aims at devices receiving and demodulating
|
|
Teletext data [<xref linkend="ets300706" />, <xref linkend="itu653" />], evaluating the
|
|
Teletext packages and storing formatted pages in cache memory. Such
|
|
devices are usually implemented as microcontrollers with serial
|
|
interface (I<superscript>2</superscript>C) and can be found on older
|
|
TV cards, dedicated Teletext decoding cards and home-brew devices
|
|
connected to the PC parallel port.</para>
|
|
|
|
<para>The Teletext API was designed by Martin Buck. It is defined in
|
|
the kernel header file <filename>linux/videotext.h</filename>, the
|
|
specification is available from <ulink url="ftp://ftp.gwdg.de/pub/linux/misc/videotext/">
|
|
ftp://ftp.gwdg.de/pub/linux/misc/videotext/</ulink>. (Videotext is the name of
|
|
the German public television Teletext service.) Conventional character
|
|
device file names are <filename>/dev/vtx</filename> and
|
|
<filename>/dev/vttuner</filename>, with device number 83, 0 and 83, 16
|
|
respectively. A similar interface exists for the Philips SAA5249
|
|
Teletext decoder [specification?] with character device file names
|
|
<filename>/dev/tlkN</filename>, device number 102, N.</para>
|
|
|
|
<para>Eventually the Teletext API was integrated into the V4L API
|
|
with character device file names <filename>/dev/vtx0</filename> to
|
|
<filename>/dev/vtx31</filename>, device major number 81, minor numbers
|
|
192 to 223. For reference the V4L Teletext API specification is
|
|
reproduced here in full: "Teletext interfaces talk the existing VTX
|
|
API." Teletext devices with major number 83 and 102 will be removed in
|
|
Linux 2.6.</para>
|
|
|
|
<para>There are no plans to replace the Teletext API or to integrate
|
|
it into V4L2. Please write to the linux-media mailing list: &v4l-ml;
|
|
when the need arises.</para>
|
|
|
|
<!--
|
|
Local Variables:
|
|
mode: sgml
|
|
sgml-parent-document: "v4l2.sgml"
|
|
indent-tabs-mode: nil
|
|
End:
|
|
-->
|