1<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN""http://www.w3.org/TR/html4/loose.dtd"> 2<HTML 3><HEAD 4><TITLE 5>Teletext Interface</TITLE 6><META 7NAME="GENERATOR" 8CONTENT="Modular DocBook HTML Stylesheet Version 1.79"><LINK 9REL="HOME" 10TITLE="Video for Linux Two API Specification" 11HREF="book1.htm"><LINK 12REL="UP" 13TITLE="Interfaces" 14HREF="c6488.htm"><LINK 15REL="PREVIOUS" 16TITLE="Sliced VBI Data Interface" 17HREF="x7236.htm"><LINK 18REL="NEXT" 19TITLE="Radio Interface" 20HREF="x7578.htm"></HEAD 21><BODY 22CLASS="SECTION" 23BGCOLOR="#FFFFFF" 24TEXT="#000000" 25LINK="#0000FF" 26VLINK="#840084" 27ALINK="#0000FF" 28><DIV 29CLASS="NAVHEADER" 30><TABLE 31SUMMARY="Header navigation table" 32WIDTH="100%" 33BORDER="0" 34CELLPADDING="0" 35CELLSPACING="0" 36><TR 37><TH 38COLSPAN="3" 39ALIGN="center" 40>Video for Linux Two API Specification: Revision 0.24</TH 41></TR 42><TR 43><TD 44WIDTH="10%" 45ALIGN="left" 46VALIGN="bottom" 47><A 48HREF="x7236.htm" 49ACCESSKEY="P" 50>Prev</A 51></TD 52><TD 53WIDTH="80%" 54ALIGN="center" 55VALIGN="bottom" 56>Chapter 4. Interfaces</TD 57><TD 58WIDTH="10%" 59ALIGN="right" 60VALIGN="bottom" 61><A 62HREF="x7578.htm" 63ACCESSKEY="N" 64>Next</A 65></TD 66></TR 67></TABLE 68><HR 69ALIGN="LEFT" 70WIDTH="100%"></DIV 71><DIV 72CLASS="SECTION" 73><H1 74CLASS="SECTION" 75><A 76NAME="TTX" 77>4.9. Teletext Interface</A 78></H1 79><P 80>This interface aims at devices receiving and demodulating 81Teletext data [<A 82HREF="b17127.htm#ETS300706" 83><ABBR 84CLASS="ABBREV" 85>ETS 300 706</ABBR 86></A 87>, <A 88HREF="b17127.htm#ITU653" 89><ABBR 90CLASS="ABBREV" 91>ITU BT.653</ABBR 92></A 93>], evaluating the 94Teletext packages and storing formatted pages in cache memory. Such 95devices are usually implemented as microcontrollers with serial 96interface (I<SUP 97>2</SUP 98>C) and can be found on older 99TV cards, dedicated Teletext decoding cards and home-brew devices 100connected to the PC parallel port.</P 101><P 102>The Teletext API was designed by Martin Buck. It is defined in 103the kernel header file <TT 104CLASS="FILENAME" 105>linux/videotext.h</TT 106>, the 107specification is available from <A 108HREF="http://home.pages.de/~videotext/" 109TARGET="_top" 110>http://home.pages.de/~videotext/</A 111>. (Videotext is the name of 112the German public television Teletext service.) Conventional character 113device file names are <TT 114CLASS="FILENAME" 115>/dev/vtx</TT 116> and 117<TT 118CLASS="FILENAME" 119>/dev/vttuner</TT 120>, with device number 83, 0 and 83, 16 121respectively. A similar interface exists for the Philips SAA5249 122Teletext decoder [specification?] with character device file names 123<TT 124CLASS="FILENAME" 125>/dev/tlkN</TT 126>, device number 102, N.</P 127><P 128>Eventually the Teletext API was integrated into the V4L API 129with character device file names <TT 130CLASS="FILENAME" 131>/dev/vtx0</TT 132> to 133<TT 134CLASS="FILENAME" 135>/dev/vtx31</TT 136>, device major number 81, minor numbers 137192 to 223. For reference the V4L Teletext API specification is 138reproduced here in full: "Teletext interfaces talk the existing VTX 139API." Teletext devices with major number 83 and 102 will be removed in 140Linux 2.6.</P 141><P 142>There are no plans to replace the Teletext API or to integrate 143it into V4L2. Please write to the Video4Linux mailing list: <A 144HREF="https://listman.redhat.com/mailman/listinfo/video4linux-list" 145TARGET="_top" 146>https://listman.redhat.com/mailman/listinfo/video4linux-list</A 147> 148when the need arises.</P 149></DIV 150><DIV 151CLASS="NAVFOOTER" 152><HR 153ALIGN="LEFT" 154WIDTH="100%"><TABLE 155SUMMARY="Footer navigation table" 156WIDTH="100%" 157BORDER="0" 158CELLPADDING="0" 159CELLSPACING="0" 160><TR 161><TD 162WIDTH="33%" 163ALIGN="left" 164VALIGN="top" 165><A 166HREF="x7236.htm" 167ACCESSKEY="P" 168>Prev</A 169></TD 170><TD 171WIDTH="34%" 172ALIGN="center" 173VALIGN="top" 174><A 175HREF="book1.htm" 176ACCESSKEY="H" 177>Home</A 178></TD 179><TD 180WIDTH="33%" 181ALIGN="right" 182VALIGN="top" 183><A 184HREF="x7578.htm" 185ACCESSKEY="N" 186>Next</A 187></TD 188></TR 189><TR 190><TD 191WIDTH="33%" 192ALIGN="left" 193VALIGN="top" 194>Sliced VBI Data Interface</TD 195><TD 196WIDTH="34%" 197ALIGN="center" 198VALIGN="top" 199><A 200HREF="c6488.htm" 201ACCESSKEY="U" 202>Up</A 203></TD 204><TD 205WIDTH="33%" 206ALIGN="right" 207VALIGN="top" 208>Radio Interface</TD 209></TR 210></TABLE 211></DIV 212></BODY 213></HTML 214> 215