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| author | Mauro Carvalho Chehab <mchehab@s-opensource.com> | 2016-07-08 16:40:06 +0200 |
|---|---|---|
| committer | Mauro Carvalho Chehab <mchehab@s-opensource.com> | 2016-07-08 16:59:40 +0200 |
| commit | 60c2820d0f6d3497975b6488e2599f8f611d8b95 (patch) | |
| tree | b3b03707c6438ea9b99cc57e847ebf517f968ab1 /Documentation/media/uapi/v4l/dev-teletext.rst | |
| parent | doc-rst: remove an invalid include from the docs (diff) | |
| download | linux-60c2820d0f6d3497975b6488e2599f8f611d8b95.tar.xz linux-60c2820d0f6d3497975b6488e2599f8f611d8b95.zip | |
doc_rst: rename the media Sphinx suff to Documentation/media
The name of the subsystem is "media", and not "linux_tv". Also,
as we plan to add other stuff there in the future, let's
rename also the media uAPI book to media_uapi, to make it
clearer.
No functional changes.
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
Diffstat (limited to 'Documentation/media/uapi/v4l/dev-teletext.rst')
| -rw-r--r-- | Documentation/media/uapi/v4l/dev-teletext.rst | 34 |
1 files changed, 34 insertions, 0 deletions
diff --git a/Documentation/media/uapi/v4l/dev-teletext.rst b/Documentation/media/uapi/v4l/dev-teletext.rst new file mode 100644 index 000000000000..2648f6b37ea3 --- /dev/null +++ b/Documentation/media/uapi/v4l/dev-teletext.rst @@ -0,0 +1,34 @@ +.. -*- coding: utf-8; mode: rst -*- + +.. _ttx: + +****************** +Teletext Interface +****************** + +This interface was aimed at devices receiving and demodulating Teletext +data [:ref:`ets300706`, :ref:`itu653`], evaluating the Teletext +packages and storing formatted pages in cache memory. Such devices are +usually implemented as microcontrollers with serial interface +(I:sup:`2`\ C) and could be found on old TV cards, dedicated Teletext +decoding cards and home-brew devices connected to the PC parallel port. + +The Teletext API was designed by Martin Buck. It was defined in the +kernel header file ``linux/videotext.h``, the specification is available +from +`ftp://ftp.gwdg.de/pub/linux/misc/videotext/ <ftp://ftp.gwdg.de/pub/linux/misc/videotext/>`__. +(Videotext is the name of the German public television Teletext +service.) + +Eventually the Teletext API was integrated into the V4L API with +character device file names ``/dev/vtx0`` to ``/dev/vtx31``, device +major number 81, minor numbers 192 to 223. + +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. + +Modern devices all use the :ref:`raw <raw-vbi>` or +:ref:`sliced` VBI API. |