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>ioctl VIDIOC_QUERYSTD</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="Function Reference" 14HREF="r7624.htm"><LINK 15REL="PREVIOUS" 16TITLE="ioctl VIDIOC_QUERYCTRL, VIDIOC_QUERYMENU" 17HREF="r13317.htm"><LINK 18REL="NEXT" 19TITLE="ioctl VIDIOC_REQBUFS" 20HREF="r13696.htm"></HEAD 21><BODY 22CLASS="REFENTRY" 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="r13317.htm" 49ACCESSKEY="P" 50>Prev</A 51></TD 52><TD 53WIDTH="80%" 54ALIGN="center" 55VALIGN="bottom" 56></TD 57><TD 58WIDTH="10%" 59ALIGN="right" 60VALIGN="bottom" 61><A 62HREF="r13696.htm" 63ACCESSKEY="N" 64>Next</A 65></TD 66></TR 67></TABLE 68><HR 69ALIGN="LEFT" 70WIDTH="100%"></DIV 71><H1 72><A 73NAME="VIDIOC-QUERYSTD" 74></A 75>ioctl VIDIOC_QUERYSTD</H1 76><DIV 77CLASS="REFNAMEDIV" 78><A 79NAME="AEN13645" 80></A 81><H2 82>Name</H2 83>VIDIOC_QUERYSTD -- Sense the video standard received by the current 84input</DIV 85><DIV 86CLASS="REFSYNOPSISDIV" 87><A 88NAME="AEN13648" 89></A 90><H2 91>Synopsis</H2 92><DIV 93CLASS="FUNCSYNOPSIS" 94><P 95></P 96><A 97NAME="AEN13649" 98></A 99><P 100><CODE 101><CODE 102CLASS="FUNCDEF" 103>int ioctl</CODE 104>(int fd, int request, v4l2_std_id *argp);</CODE 105></P 106><P 107></P 108></DIV 109></DIV 110><DIV 111CLASS="REFSECT1" 112><A 113NAME="AEN13659" 114></A 115><H2 116>Arguments</H2 117><P 118></P 119><DIV 120CLASS="VARIABLELIST" 121><DL 122><DT 123><CODE 124CLASS="PARAMETER" 125>fd</CODE 126></DT 127><DD 128><P 129>File descriptor returned by <A 130HREF="r14090.htm" 131><CODE 132CLASS="FUNCTION" 133>open()</CODE 134></A 135>.</P 136></DD 137><DT 138><CODE 139CLASS="PARAMETER" 140>request</CODE 141></DT 142><DD 143><P 144>VIDIOC_QUERYSTD</P 145></DD 146><DT 147><CODE 148CLASS="PARAMETER" 149>argp</CODE 150></DT 151><DD 152><P 153></P 154></DD 155></DL 156></DIV 157></DIV 158><DIV 159CLASS="REFSECT1" 160><A 161NAME="AEN13679" 162></A 163><H2 164>Description</H2 165><P 166>The hardware may be able to detect the current video 167standard automatically. To do so, applications call <CODE 168CLASS="CONSTANT" 169>VIDIOC_QUERYSTD</CODE 170> with a pointer to a <A 171HREF="r9288.htm#V4L2-STD-ID" 172>v4l2_std_id</A 173> type. The 174driver stores here a set of candidates, this can be a single flag or a 175set of supported standards if for example the hardware can only 176distinguish between 50 and 60 Hz systems. When detection is not 177possible or fails, the set must contain all standards supported by the 178current video input or output.</P 179></DIV 180><DIV 181CLASS="REFSECT1" 182><A 183NAME="AEN13684" 184></A 185><H2 186>Return Value</H2 187><P 188>On success <SPAN 189CLASS="RETURNVALUE" 190>0</SPAN 191> is returned, on error <SPAN 192CLASS="RETURNVALUE" 193>-1</SPAN 194> and the <CODE 195CLASS="VARNAME" 196>errno</CODE 197> variable is set appropriately:</P 198><P 199></P 200><DIV 201CLASS="VARIABLELIST" 202><DL 203><DT 204><SPAN 205CLASS="ERRORCODE" 206>EINVAL</SPAN 207></DT 208><DD 209><P 210>This ioctl is not supported.</P 211></DD 212></DL 213></DIV 214></DIV 215><DIV 216CLASS="NAVFOOTER" 217><HR 218ALIGN="LEFT" 219WIDTH="100%"><TABLE 220SUMMARY="Footer navigation table" 221WIDTH="100%" 222BORDER="0" 223CELLPADDING="0" 224CELLSPACING="0" 225><TR 226><TD 227WIDTH="33%" 228ALIGN="left" 229VALIGN="top" 230><A 231HREF="r13317.htm" 232ACCESSKEY="P" 233>Prev</A 234></TD 235><TD 236WIDTH="34%" 237ALIGN="center" 238VALIGN="top" 239><A 240HREF="book1.htm" 241ACCESSKEY="H" 242>Home</A 243></TD 244><TD 245WIDTH="33%" 246ALIGN="right" 247VALIGN="top" 248><A 249HREF="r13696.htm" 250ACCESSKEY="N" 251>Next</A 252></TD 253></TR 254><TR 255><TD 256WIDTH="33%" 257ALIGN="left" 258VALIGN="top" 259>ioctl VIDIOC_QUERYCTRL, VIDIOC_QUERYMENU</TD 260><TD 261WIDTH="34%" 262ALIGN="center" 263VALIGN="top" 264><A 265HREF="r7624.htm" 266ACCESSKEY="U" 267>Up</A 268></TD 269><TD 270WIDTH="33%" 271ALIGN="right" 272VALIGN="top" 273>ioctl VIDIOC_REQBUFS</TD 274></TR 275></TABLE 276></DIV 277></BODY 278></HTML 279> 280