From 57f0f512b273f60d52568b8c6b77e17f5636edc0 Mon Sep 17 00:00:00 2001 From: André Fabian Silva Delgado Date: Wed, 5 Aug 2015 17:04:01 -0300 Subject: Initial import --- Documentation/DocBook/media/v4l/dev-teletext.xml | 29 ++++++++++++++++++++++++ 1 file changed, 29 insertions(+) create mode 100644 Documentation/DocBook/media/v4l/dev-teletext.xml (limited to 'Documentation/DocBook/media/v4l/dev-teletext.xml') diff --git a/Documentation/DocBook/media/v4l/dev-teletext.xml b/Documentation/DocBook/media/v4l/dev-teletext.xml new file mode 100644 index 000000000..bd21c64d7 --- /dev/null +++ b/Documentation/DocBook/media/v4l/dev-teletext.xml @@ -0,0 +1,29 @@ + Teletext Interface + + This interface was aimed at devices receiving and demodulating +Teletext data [, ], evaluating the +Teletext packages and storing formatted pages in cache memory. Such +devices are usually implemented as microcontrollers with serial +interface (I2C) 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/. (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 raw or +sliced VBI API. -- cgit v1.2.3-54-g00ecf