| <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> |
| |
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