Teletext Interface
- This interface aims at devices receiving and demodulating
+ 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 can be found on older
+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 is defined in
+ 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.) Conventional character
-device file names are /dev/vtx and
-/dev/vttuner, 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
-/dev/tlkN, device number 102, N.
+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. 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.
+192 to 223.
- 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.
+ 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.