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| >Video for Linux Two API Specification: Revision 0.24</TH |
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| ><H1 |
| ><A |
| NAME="VIDIOC-CROPCAP" |
| ></A |
| >ioctl VIDIOC_CROPCAP</H1 |
| ><DIV |
| CLASS="REFNAMEDIV" |
| ><A |
| NAME="AEN7775" |
| ></A |
| ><H2 |
| >Name</H2 |
| >VIDIOC_CROPCAP -- Information about the video cropping and scaling abilities</DIV |
| ><DIV |
| CLASS="REFSYNOPSISDIV" |
| ><A |
| NAME="AEN7778" |
| ></A |
| ><H2 |
| >Synopsis</H2 |
| ><DIV |
| CLASS="FUNCSYNOPSIS" |
| ><P |
| ></P |
| ><A |
| NAME="AEN7779" |
| ></A |
| ><P |
| ><CODE |
| ><CODE |
| CLASS="FUNCDEF" |
| >int ioctl</CODE |
| >(int fd, int request, struct v4l2_cropcap |
| *argp);</CODE |
| ></P |
| ><P |
| ></P |
| ></DIV |
| ></DIV |
| ><DIV |
| CLASS="REFSECT1" |
| ><A |
| NAME="AEN7789" |
| ></A |
| ><H2 |
| >Arguments</H2 |
| ><P |
| ></P |
| ><DIV |
| CLASS="VARIABLELIST" |
| ><DL |
| ><DT |
| ><CODE |
| CLASS="PARAMETER" |
| >fd</CODE |
| ></DT |
| ><DD |
| ><P |
| >File descriptor returned by <A |
| HREF="r14090.htm" |
| ><CODE |
| CLASS="FUNCTION" |
| >open()</CODE |
| ></A |
| >.</P |
| ></DD |
| ><DT |
| ><CODE |
| CLASS="PARAMETER" |
| >request</CODE |
| ></DT |
| ><DD |
| ><P |
| >VIDIOC_CROPCAP</P |
| ></DD |
| ><DT |
| ><CODE |
| CLASS="PARAMETER" |
| >argp</CODE |
| ></DT |
| ><DD |
| ><P |
| ></P |
| ></DD |
| ></DL |
| ></DIV |
| ></DIV |
| ><DIV |
| CLASS="REFSECT1" |
| ><A |
| NAME="AEN7809" |
| ></A |
| ><H2 |
| >Description</H2 |
| ><P |
| >Applications use this function to query the cropping |
| limits, the pixel aspect of images and to calculate scale factors. |
| They set the <CODE |
| CLASS="STRUCTFIELD" |
| >type</CODE |
| > field of a v4l2_cropcap |
| structure to the respective buffer (stream) type and call the |
| <CODE |
| CLASS="CONSTANT" |
| >VIDIOC_CROPCAP</CODE |
| > ioctl with a pointer to this |
| structure. Drivers fill the rest of the structure. The results are |
| constant except when switching the video standard. Remember this |
| switch can occur implicit when switching the video input or |
| output.</P |
| ><DIV |
| CLASS="TABLE" |
| ><A |
| NAME="V4L2-CROPCAP" |
| ></A |
| ><P |
| ><B |
| >Table 1. struct <CODE |
| CLASS="STRUCTNAME" |
| >v4l2_cropcap</CODE |
| ></B |
| ></P |
| ><TABLE |
| BORDER="0" |
| FRAME="void" |
| WIDTH="100%" |
| CLASS="CALSTABLE" |
| ><COL |
| WIDTH="25%" |
| TITLE="C1"><COL |
| WIDTH="25%" |
| TITLE="C2"><COL |
| WIDTH="50%" |
| TITLE="C3"><TBODY |
| VALIGN="TOP" |
| ><TR |
| ><TD |
| >enum <A |
| HREF="x5953.htm#V4L2-BUF-TYPE" |
| >v4l2_buf_type</A |
| ></TD |
| ><TD |
| ><CODE |
| CLASS="STRUCTFIELD" |
| >type</CODE |
| ></TD |
| ><TD |
| >Type of the data stream, set by the application. |
| Only these types are valid here: |
| <CODE |
| CLASS="CONSTANT" |
| >V4L2_BUF_TYPE_VIDEO_CAPTURE</CODE |
| >, |
| <CODE |
| CLASS="CONSTANT" |
| >V4L2_BUF_TYPE_VIDEO_OUTPUT</CODE |
| >, |
| <CODE |
| CLASS="CONSTANT" |
| >V4L2_BUF_TYPE_VIDEO_OVERLAY</CODE |
| >, and custom (driver |
| defined) types with code <CODE |
| CLASS="CONSTANT" |
| >V4L2_BUF_TYPE_PRIVATE</CODE |
| > |
| and higher.</TD |
| ></TR |
| ><TR |
| ><TD |
| >struct <A |
| HREF="r7771.htm#V4L2-RECT-CROP" |
| >v4l2_rect</A |
| ></TD |
| ><TD |
| ><CODE |
| CLASS="STRUCTFIELD" |
| >bounds</CODE |
| ></TD |
| ><TD |
| >Defines the window within capturing or output is |
| possible, this may exclude for example the horizontal and vertical |
| blanking areas. The cropping rectangle cannot exceed these limits. |
| Width and height are defined in pixels, the driver writer is free to |
| choose origin and units of the coordinate system in the analog |
| domain.</TD |
| ></TR |
| ><TR |
| ><TD |
| >struct <A |
| HREF="r7771.htm#V4L2-RECT-CROP" |
| >v4l2_rect</A |
| ></TD |
| ><TD |
| ><CODE |
| CLASS="STRUCTFIELD" |
| >defrect</CODE |
| ></TD |
| ><TD |
| >Default cropping rectangle, it shall cover the |
| "whole picture". Assuming pixel aspect 1/1 this could be for example a |
| 640 × 480 rectangle for NTSC, a |
| 768 × 576 rectangle for PAL and SECAM centered over |
| the active picture area. The same co-ordinate system as for |
| <CODE |
| CLASS="STRUCTFIELD" |
| >bounds</CODE |
| > is used.</TD |
| ></TR |
| ><TR |
| ><TD |
| >struct <A |
| HREF="r9288.htm#V4L2-FRACT" |
| >v4l2_fract</A |
| ></TD |
| ><TD |
| ><CODE |
| CLASS="STRUCTFIELD" |
| >pixelaspect</CODE |
| ></TD |
| ><TD |
| ><P |
| >This is the pixel aspect (y / x) when no |
| scaling is applied, the ratio of the actual sampling |
| frequency and the frequency required to get square |
| pixels.</P |
| ><P |
| >When cropping coordinates refer to square pixels, |
| the driver sets <CODE |
| CLASS="STRUCTFIELD" |
| >pixelaspect</CODE |
| > to 1/1. Other |
| common values are 54/59 for PAL and SECAM, 11/10 for NTSC sampled |
| according to [<A |
| HREF="b17127.htm#ITU601" |
| ><ABBR |
| CLASS="ABBREV" |
| >ITU BT.601</ABBR |
| ></A |
| >].</P |
| ></TD |
| ></TR |
| ></TBODY |
| ></TABLE |
| ></DIV |
| ><DIV |
| CLASS="TABLE" |
| ><A |
| NAME="V4L2-RECT-CROP" |
| ></A |
| ><P |
| ><B |
| >Table 2. struct <CODE |
| CLASS="STRUCTNAME" |
| >v4l2_rect</CODE |
| ></B |
| ></P |
| ><TABLE |
| BORDER="0" |
| FRAME="void" |
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| CLASS="CALSTABLE" |
| ><COL |
| WIDTH="25%" |
| TITLE="C1"><COL |
| WIDTH="25%" |
| TITLE="C2"><COL |
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| VALIGN="TOP" |
| ><TR |
| ><TD |
| >__s32</TD |
| ><TD |
| ><CODE |
| CLASS="STRUCTFIELD" |
| >left</CODE |
| ></TD |
| ><TD |
| >Horizontal offset of the top, left corner of the |
| rectangle, in pixels.</TD |
| ></TR |
| ><TR |
| ><TD |
| >__s32</TD |
| ><TD |
| ><CODE |
| CLASS="STRUCTFIELD" |
| >top</CODE |
| ></TD |
| ><TD |
| >Vertical offset of the top, left corner of the |
| rectangle, in pixels.</TD |
| ></TR |
| ><TR |
| ><TD |
| >__s32</TD |
| ><TD |
| ><CODE |
| CLASS="STRUCTFIELD" |
| >width</CODE |
| ></TD |
| ><TD |
| >Width of the rectangle, in pixels.</TD |
| ></TR |
| ><TR |
| ><TD |
| >__s32</TD |
| ><TD |
| ><CODE |
| CLASS="STRUCTFIELD" |
| >height</CODE |
| ></TD |
| ><TD |
| >Height of the rectangle, in pixels. Width |
| and height cannot be negative, the fields are signed for |
| hysterical reasons. </TD |
| ></TR |
| ></TBODY |
| ></TABLE |
| ></DIV |
| ></DIV |
| ><DIV |
| CLASS="REFSECT1" |
| ><A |
| NAME="AEN7885" |
| ></A |
| ><H2 |
| >Return Value</H2 |
| ><P |
| >On success <SPAN |
| CLASS="RETURNVALUE" |
| >0</SPAN |
| > is returned, on error <SPAN |
| CLASS="RETURNVALUE" |
| >-1</SPAN |
| > and the <CODE |
| CLASS="VARNAME" |
| >errno</CODE |
| > variable is set appropriately:</P |
| ><P |
| ></P |
| ><DIV |
| CLASS="VARIABLELIST" |
| ><DL |
| ><DT |
| ><SPAN |
| CLASS="ERRORCODE" |
| >EINVAL</SPAN |
| ></DT |
| ><DD |
| ><P |
| >The struct <A |
| HREF="r7771.htm#V4L2-CROPCAP" |
| >v4l2_cropcap</A |
| > <CODE |
| CLASS="STRUCTFIELD" |
| >type</CODE |
| > is |
| invalid or the ioctl is not supported. This is not permitted for |
| video capture, output and overlay devices, which must support |
| <CODE |
| CLASS="CONSTANT" |
| >VIDIOC_CROPCAP</CODE |
| >.</P |
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| ></DL |
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