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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 @@ | |||
1 | <title>Teletext Interface</title> | 1 | <title>Teletext Interface</title> |
2 | 2 | ||
3 | <para>This interface aims at devices receiving and demodulating | 3 | <para>This interface was aimed at devices receiving and demodulating |
4 | Teletext data [<xref linkend="ets300706" />, <xref linkend="itu653" />], evaluating the | 4 | Teletext data [<xref linkend="ets300706" />, <xref linkend="itu653" />], evaluating the |
5 | Teletext packages and storing formatted pages in cache memory. Such | 5 | Teletext packages and storing formatted pages in cache memory. Such |
6 | devices are usually implemented as microcontrollers with serial | 6 | devices are usually implemented as microcontrollers with serial |
7 | interface (I<superscript>2</superscript>C) and can be found on older | 7 | interface (I<superscript>2</superscript>C) and could be found on old |
8 | TV cards, dedicated Teletext decoding cards and home-brew devices | 8 | TV cards, dedicated Teletext decoding cards and home-brew devices |
9 | connected to the PC parallel port.</para> | 9 | connected to the PC parallel port.</para> |
10 | 10 | ||
11 | <para>The Teletext API was designed by Martin Buck. It is defined in | 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 | 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/"> | 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 | 14 | ftp://ftp.gwdg.de/pub/linux/misc/videotext/</ulink>. (Videotext is the name of |
15 | the German public television Teletext service.) Conventional character | 15 | the German public television Teletext service.)</para> |
16 | device file names are <filename>/dev/vtx</filename> and | ||
17 | <filename>/dev/vttuner</filename>, with device number 83, 0 and 83, 16 | ||
18 | respectively. A similar interface exists for the Philips SAA5249 | ||
19 | Teletext decoder [specification?] with character device file names | ||
20 | <filename>/dev/tlkN</filename>, device number 102, N.</para> | ||
21 | 16 | ||
22 | <para>Eventually the Teletext API was integrated into the V4L API | 17 | <para>Eventually the Teletext API was integrated into the V4L API |
23 | with character device file names <filename>/dev/vtx0</filename> to | 18 | with character device file names <filename>/dev/vtx0</filename> to |
24 | <filename>/dev/vtx31</filename>, device major number 81, minor numbers | 19 | <filename>/dev/vtx31</filename>, device major number 81, minor numbers |
25 | 192 to 223. For reference the V4L Teletext API specification is | 20 | 192 to 223.</para> |
26 | reproduced here in full: "Teletext interfaces talk the existing VTX | ||
27 | API." Teletext devices with major number 83 and 102 will be removed in | ||
28 | Linux 2.6.</para> | ||
29 | 21 | ||
30 | <para>There are no plans to replace the Teletext API or to integrate | 22 | <para>However, teletext decoders were quickly replaced by more |
31 | it into V4L2. Please write to the linux-media mailing list: &v4l-ml; | 23 | generic VBI demodulators and those dedicated teletext decoders no longer exist. |
32 | when the need arises.</para> | 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> | ||
33 | 30 | ||
34 | <!-- | 31 | <!-- |
35 | Local Variables: | 32 | Local Variables: |