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Diffstat (limited to 'Documentation/DocBook/v4l/dev-teletext.xml')
| -rw-r--r-- | Documentation/DocBook/v4l/dev-teletext.xml | 29 |
1 files changed, 13 insertions, 16 deletions
diff --git a/Documentation/DocBook/v4l/dev-teletext.xml b/Documentation/DocBook/v4l/dev-teletext.xml index 76184e8ed618..414b1cfff9f4 100644 --- a/Documentation/DocBook/v4l/dev-teletext.xml +++ b/Documentation/DocBook/v4l/dev-teletext.xml @@ -1,35 +1,32 @@ <title>Teletext Interface</title> - <para>This interface aims at devices receiving and demodulating + <para>This interface was aimed 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 +interface (I<superscript>2</superscript>C) and could be found on old 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 + <para>The Teletext API was designed by Martin Buck. It was 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> +the German public television Teletext service.)</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> +192 to 223.</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> + <para>However, teletext decoders were quickly replaced by more +generic VBI demodulators and those dedicated teletext decoders no longer exist. +For many years the vtx devices were still around, even though nobody used +them. So the decision was made to finally remove support for the Teletext API in +kernel 2.6.37.</para> + + <para>Modern devices all use the <link linkend="raw-vbi">raw</link> or +<link linkend="sliced">sliced</link> VBI API.</para> <!-- Local Variables: |