4.9. Teletext Interface

This interface aims at devices receiving and demodulating Teletext data [[ETS 300 706], [ITU BT.653]], 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 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 kernel header file linux/videotext.h, the specification is available from http://home.pages.de/~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.

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.

There are no plans to replace the Teletext API or to integrate it into V4L2. Please write to the linux-media mailing list: https://linuxtv.org/lists.php when the need arises.