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     40 >Video for Linux Two API Specification: Revision 0.24</TH
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     73 ><H1
     74 CLASS="SECTION"
     75 ><A
     76 NAME="VIDEO"
     77 >1.4. Video Inputs and Outputs</A
     78 ></H1
     79 ><P
     80 >Video inputs and outputs are physical connectors of a
     81 device. These can be for example RF connectors (antenna/cable), CVBS
     82 a.k.a. Composite Video, S-Video or RGB connectors. Only video and VBI
     83 capture devices have inputs, output devices have outputs, at least one
     84 each. Radio devices have no video inputs or outputs.</P
     85 ><P
     86 >To learn about the number and attributes of the
     87 available inputs and outputs applications can enumerate them with the
     88 <A
     89 HREF="r8936.htm"
     90 ><CODE
     91 CLASS="CONSTANT"
     92 >VIDIOC_ENUMINPUT</CODE
     93 ></A
     94 > and <A
     95 HREF="r9149.htm"
     96 ><CODE
     97 CLASS="CONSTANT"
     98 >VIDIOC_ENUMOUTPUT</CODE
     99 ></A
    100 > ioctl, respectively. The
    101 struct&nbsp;<A
    102 HREF="r8936.htm#V4L2-INPUT"
    103 >v4l2_input</A
    104 > returned by the <CODE
    105 CLASS="CONSTANT"
    106 >VIDIOC_ENUMINPUT</CODE
    107 >
    108 ioctl also contains signal status information applicable when the
    109 current video input is queried.</P
    110 ><P
    111 >The <A
    112 HREF="r11217.htm"
    113 ><CODE
    114 CLASS="CONSTANT"
    115 >VIDIOC_G_INPUT</CODE
    116 ></A
    117 > and <A
    118 HREF="r11612.htm"
    119 ><CODE
    120 CLASS="CONSTANT"
    121 >VIDIOC_G_OUTPUT</CODE
    122 ></A
    123 > ioctl return the
    124 index of the current video input or output. To select a different
    125 input or output applications call the <A
    126 HREF="r11217.htm"
    127 ><CODE
    128 CLASS="CONSTANT"
    129 >VIDIOC_S_INPUT</CODE
    130 ></A
    131 > and
    132 <A
    133 HREF="r11612.htm"
    134 ><CODE
    135 CLASS="CONSTANT"
    136 >VIDIOC_S_OUTPUT</CODE
    137 ></A
    138 > ioctl. Drivers must implement all the input ioctls
    139 when the device has one or more inputs, all the output ioctls when the
    140 device has one or more outputs.</P
    141 ><DIV
    142 CLASS="EXAMPLE"
    143 ><A
    144 NAME="AEN328"
    145 ></A
    146 ><P
    147 ><B
    148 >Example 1-1. Information about the current video input</B
    149 ></P
    150 ><PRE
    151 CLASS="PROGRAMLISTING"
    152 >struct&nbsp;<A
    153 HREF="r8936.htm#V4L2-INPUT"
    154 >v4l2_input</A
    155 > input;
    156 int index;
    157 
    158 if (-1 == ioctl (fd, <A
    159 HREF="r11217.htm"
    160 ><CODE
    161 CLASS="CONSTANT"
    162 >VIDIOC_G_INPUT</CODE
    163 ></A
    164 >, &amp;index)) {
    165         perror ("VIDIOC_G_INPUT");
    166         exit (EXIT_FAILURE);
    167 }
    168 
    169 memset (&amp;input, 0, sizeof (input));
    170 input.index = index;
    171 
    172 if (-1 == ioctl (fd, <A
    173 HREF="r8936.htm"
    174 ><CODE
    175 CLASS="CONSTANT"
    176 >VIDIOC_ENUMINPUT</CODE
    177 ></A
    178 >, &amp;input)) {
    179         perror ("VIDIOC_ENUMINPUT");
    180         exit (EXIT_FAILURE);
    181 }
    182 
    183 printf ("Current input: %s\n", input.name);
    184       </PRE
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    186 ><DIV
    187 CLASS="EXAMPLE"
    188 ><A
    189 NAME="AEN336"
    190 ></A
    191 ><P
    192 ><B
    193 >Example 1-2. Switching to the first video input</B
    194 ></P
    195 ><PRE
    196 CLASS="PROGRAMLISTING"
    197 >int index;
    198 
    199 index = 0;
    200 
    201 if (-1 == ioctl (fd, <A
    202 HREF="r11217.htm"
    203 ><CODE
    204 CLASS="CONSTANT"
    205 >VIDIOC_S_INPUT</CODE
    206 ></A
    207 >, &amp;index)) {
    208         perror ("VIDIOC_S_INPUT");
    209         exit (EXIT_FAILURE);
    210 }
    211       </PRE
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