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     40 >Video for Linux Two API Specification: Revision 0.24</TH
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     56 >Chapter 4. Interfaces</TD
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     75 ><A
     76 NAME="TTX"
     77 >4.9. Teletext Interface</A
     78 ></H1
     79 ><P
     80 >This interface aims at devices receiving and demodulating
     81 Teletext data [<A
     82 HREF="b17127.htm#ETS300706"
     83 ><ABBR
     84 CLASS="ABBREV"
     85 >ETS&nbsp;300&nbsp;706</ABBR
     86 ></A
     87 >, <A
     88 HREF="b17127.htm#ITU653"
     89 ><ABBR
     90 CLASS="ABBREV"
     91 >ITU&nbsp;BT.653</ABBR
     92 ></A
     93 >], evaluating the
     94 Teletext packages and storing formatted pages in cache memory. Such
     95 devices are usually implemented as microcontrollers with serial
     96 interface (I<SUP
     97 >2</SUP
     98 >C) and can be found on older
     99 TV cards, dedicated Teletext decoding cards and home-brew devices
    100 connected to the PC parallel port.</P
    101 ><P
    102 >The Teletext API was designed by Martin Buck. It is defined in
    103 the kernel header file <TT
    104 CLASS="FILENAME"
    105 >linux/videotext.h</TT
    106 >, the
    107 specification is available from <A
    108 HREF="http://home.pages.de/~videotext/"
    109 TARGET="_top"
    110 >http://home.pages.de/~videotext/</A
    111 >. (Videotext is the name of
    112 the German public television Teletext service.) Conventional character
    113 device file names are <TT
    114 CLASS="FILENAME"
    115 >/dev/vtx</TT
    116 > and
    117 <TT
    118 CLASS="FILENAME"
    119 >/dev/vttuner</TT
    120 >, with device number 83, 0 and 83, 16
    121 respectively. A similar interface exists for the Philips SAA5249
    122 Teletext decoder [specification?] with character device file names
    123 <TT
    124 CLASS="FILENAME"
    125 >/dev/tlkN</TT
    126 >, device number 102, N.</P
    127 ><P
    128 >Eventually the Teletext API was integrated into the V4L API
    129 with character device file names <TT
    130 CLASS="FILENAME"
    131 >/dev/vtx0</TT
    132 > to
    133 <TT
    134 CLASS="FILENAME"
    135 >/dev/vtx31</TT
    136 >, device major number 81, minor numbers
    137 192 to 223. For reference the V4L Teletext API specification is
    138 reproduced here in full: "Teletext interfaces talk the existing VTX
    139 API." Teletext devices with major number 83 and 102 will be removed in
    140 Linux 2.6.</P
    141 ><P
    142 >There are no plans to replace the Teletext API or to integrate
    143 it into V4L2. Please write to the Video4Linux mailing list: <A
    144 HREF="https://listman.redhat.com/mailman/listinfo/video4linux-list"
    145 TARGET="_top"
    146 >https://listman.redhat.com/mailman/listinfo/video4linux-list</A
    147 >
    148 when the need arises.</P
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