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| >Video for Linux Two API Specification: Revision 0.24</TH |
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| ><H1 |
| ><A |
| NAME="VIDIOC-ENUM-FRAMEINTERVALS" |
| ></A |
| >ioctl VIDIOC_ENUM_FRAMEINTERVALS</H1 |
| ><DIV |
| CLASS="REFNAMEDIV" |
| ><A |
| NAME="AEN8728" |
| ></A |
| ><H2 |
| >Name</H2 |
| >VIDIOC_ENUM_FRAMEINTERVALS -- Enumerate frame intervals</DIV |
| ><DIV |
| CLASS="REFSYNOPSISDIV" |
| ><A |
| NAME="AEN8731" |
| ></A |
| ><H2 |
| >Synopsis</H2 |
| ><DIV |
| CLASS="FUNCSYNOPSIS" |
| ><P |
| ></P |
| ><A |
| NAME="AEN8732" |
| ></A |
| ><P |
| ><CODE |
| ><CODE |
| CLASS="FUNCDEF" |
| >int ioctl</CODE |
| >(int fd, int request, struct v4l2_frmivalenum *argp);</CODE |
| ></P |
| ><P |
| ></P |
| ></DIV |
| ></DIV |
| ><DIV |
| CLASS="REFSECT1" |
| ><A |
| NAME="AEN8742" |
| ></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_ENUM_FRAMEINTERVALS</P |
| ></DD |
| ><DT |
| ><CODE |
| CLASS="PARAMETER" |
| >argp</CODE |
| ></DT |
| ><DD |
| ><P |
| >Pointer to a struct <A |
| HREF="r8724.htm#V4L2-FRMIVALENUM" |
| >v4l2_frmivalenum</A |
| > structure that |
| contains a pixel format and size and receives a frame interval.</P |
| ></DD |
| ></DL |
| ></DIV |
| ></DIV |
| ><DIV |
| CLASS="REFSECT1" |
| ><A |
| NAME="AEN8763" |
| ></A |
| ><H2 |
| >Description</H2 |
| ><P |
| >This ioctl allows applications to enumerate all frame |
| intervals that the device supports for the given pixel format and |
| frame size.</P |
| ><P |
| >The supported pixel formats and frame sizes can be obtained |
| by using the <A |
| HREF="r8367.htm" |
| ><CODE |
| CLASS="CONSTANT" |
| >VIDIOC_ENUM_FMT</CODE |
| ></A |
| > and <A |
| HREF="r8494.htm" |
| ><CODE |
| CLASS="CONSTANT" |
| >VIDIOC_ENUM_FRAMESIZES</CODE |
| ></A |
| > |
| functions.</P |
| ><P |
| >The return value and the content of the |
| <CODE |
| CLASS="STRUCTFIELD" |
| >v4l2_frmivalenum.type</CODE |
| > field depend on the |
| type of frame intervals the device supports. Here are the semantics of |
| the function for the different cases:</P |
| ><P |
| ></P |
| ><UL |
| ><LI |
| ><P |
| ><SPAN |
| CLASS="bold" |
| ><B |
| CLASS="EMPHASIS" |
| >Discrete:</B |
| ></SPAN |
| > The function |
| returns success if the given index value (zero-based) is valid. The |
| application should increase the index by one for each call until |
| <CODE |
| CLASS="CONSTANT" |
| >EINVAL</CODE |
| > is returned. The `v4l2_frmivalenum.type` |
| field is set to `V4L2_FRMIVAL_TYPE_DISCRETE` by the driver. Of the |
| union only the `discrete` member is valid.</P |
| ></LI |
| ><LI |
| ><P |
| ><SPAN |
| CLASS="bold" |
| ><B |
| CLASS="EMPHASIS" |
| >Step-wise:</B |
| ></SPAN |
| > The function |
| returns success if the given index value is zero and |
| <CODE |
| CLASS="CONSTANT" |
| >EINVAL</CODE |
| > for any other index value. The |
| <CODE |
| CLASS="STRUCTFIELD" |
| >v4l2_frmivalenum.type</CODE |
| > field is set to |
| <CODE |
| CLASS="CONSTANT" |
| >V4L2_FRMIVAL_TYPE_STEPWISE</CODE |
| > by the driver. Of the |
| union only the <CODE |
| CLASS="STRUCTFIELD" |
| >stepwise</CODE |
| > member is |
| valid.</P |
| ></LI |
| ><LI |
| ><P |
| ><SPAN |
| CLASS="bold" |
| ><B |
| CLASS="EMPHASIS" |
| >Continuous:</B |
| ></SPAN |
| > This is a |
| special case of the step-wise type above. The function returns success |
| if the given index value is zero and <CODE |
| CLASS="CONSTANT" |
| >EINVAL</CODE |
| > for |
| any other index value. The |
| <CODE |
| CLASS="STRUCTFIELD" |
| >v4l2_frmivalenum.type</CODE |
| > field is set to |
| <CODE |
| CLASS="CONSTANT" |
| >V4L2_FRMIVAL_TYPE_CONTINUOUS</CODE |
| > by the driver. Of |
| the union only the <CODE |
| CLASS="STRUCTFIELD" |
| >stepwise</CODE |
| > member is valid |
| and the <CODE |
| CLASS="STRUCTFIELD" |
| >step</CODE |
| > value is set to 1.</P |
| ></LI |
| ></UL |
| ><P |
| >When the application calls the function with index zero, it |
| must check the <CODE |
| CLASS="STRUCTFIELD" |
| >type</CODE |
| > field to determine the |
| type of frame interval enumeration the device supports. Only for the |
| <CODE |
| CLASS="CONSTANT" |
| >V4L2_FRMIVAL_TYPE_DISCRETE</CODE |
| > type does it make |
| sense to increase the index value to receive more frame |
| intervals.</P |
| ><P |
| >Note that the order in which the frame intervals are |
| returned has no special meaning. In particular does it not say |
| anything about potential default frame intervals.</P |
| ><P |
| >Applications can assume that the enumeration data does not |
| change without any interaction from the application itself. This means |
| that the enumeration data is consistent if the application does not |
| perform any other ioctl calls while it runs the frame interval |
| enumeration.</P |
| ></DIV |
| ><DIV |
| CLASS="REFSECT1" |
| ><A |
| NAME="AEN8798" |
| ></A |
| ><H2 |
| >Notes</H2 |
| ><P |
| ></P |
| ><UL |
| ><LI |
| ><P |
| ><SPAN |
| CLASS="bold" |
| ><B |
| CLASS="EMPHASIS" |
| >Frame intervals and frame |
| rates:</B |
| ></SPAN |
| > The V4L2 API uses frame intervals instead of frame |
| rates. Given the frame interval the frame rate can be computed as |
| follows:<PRE |
| CLASS="SCREEN" |
| >frame_rate = 1 / frame_interval</PRE |
| ></P |
| ></LI |
| ></UL |
| ></DIV |
| ><DIV |
| CLASS="REFSECT1" |
| ><A |
| NAME="AEN8805" |
| ></A |
| ><H2 |
| >Structs</H2 |
| ><P |
| >In the structs below, <SPAN |
| CLASS="emphasis" |
| ><I |
| CLASS="EMPHASIS" |
| >IN</I |
| ></SPAN |
| > denotes a |
| value that has to be filled in by the application, |
| <SPAN |
| CLASS="emphasis" |
| ><I |
| CLASS="EMPHASIS" |
| >OUT</I |
| ></SPAN |
| > denotes values that the driver fills in. The |
| application should zero out all members except for the |
| <SPAN |
| CLASS="emphasis" |
| ><I |
| CLASS="EMPHASIS" |
| >IN</I |
| ></SPAN |
| > fields.</P |
| ><DIV |
| CLASS="TABLE" |
| ><A |
| NAME="V4L2-FRMIVAL-STEPWISE" |
| ></A |
| ><P |
| ><B |
| >Table 1. struct <CODE |
| CLASS="STRUCTNAME" |
| >v4l2_frmival_stepwise</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 |
| >struct <A |
| HREF="r9288.htm#V4L2-FRACT" |
| >v4l2_fract</A |
| ></TD |
| ><TD |
| ><CODE |
| CLASS="STRUCTFIELD" |
| >min</CODE |
| ></TD |
| ><TD |
| >Minimum frame interval [s].</TD |
| ></TR |
| ><TR |
| ><TD |
| >struct <A |
| HREF="r9288.htm#V4L2-FRACT" |
| >v4l2_fract</A |
| ></TD |
| ><TD |
| ><CODE |
| CLASS="STRUCTFIELD" |
| >max</CODE |
| ></TD |
| ><TD |
| >Maximum frame interval [s].</TD |
| ></TR |
| ><TR |
| ><TD |
| >struct <A |
| HREF="r9288.htm#V4L2-FRACT" |
| >v4l2_fract</A |
| ></TD |
| ><TD |
| ><CODE |
| CLASS="STRUCTFIELD" |
| >step</CODE |
| ></TD |
| ><TD |
| >Frame interval step size [s].</TD |
| ></TR |
| ></TBODY |
| ></TABLE |
| ></DIV |
| ><DIV |
| CLASS="TABLE" |
| ><A |
| NAME="V4L2-FRMIVALENUM" |
| ></A |
| ><P |
| ><B |
| >Table 2. struct <CODE |
| CLASS="STRUCTNAME" |
| >v4l2_frmivalenum</CODE |
| ></B |
| ></P |
| ><TABLE |
| BORDER="0" |
| FRAME="void" |
| WIDTH="100%" |
| CLASS="CALSTABLE" |
| ><COL |
| WIDTH="25%" |
| TITLE="C1"><COL |
| WIDTH="25%" |
| TITLE="C2"><COL |
| WIDTH="25%" |
| TITLE="C3"><COL |
| WIDTH="25%" |
| TITLE="C4"><TBODY |
| VALIGN="TOP" |
| ><TR |
| ><TD |
| >__u32</TD |
| ><TD |
| ><CODE |
| CLASS="STRUCTFIELD" |
| >index</CODE |
| ></TD |
| ><TD |
| > </TD |
| ><TD |
| >IN: Index of the given frame interval in the |
| enumeration.</TD |
| ></TR |
| ><TR |
| ><TD |
| >__u32</TD |
| ><TD |
| ><CODE |
| CLASS="STRUCTFIELD" |
| >pixel_format</CODE |
| ></TD |
| ><TD |
| > </TD |
| ><TD |
| >IN: Pixel format for which the frame intervals are |
| enumerated.</TD |
| ></TR |
| ><TR |
| ><TD |
| >__u32</TD |
| ><TD |
| ><CODE |
| CLASS="STRUCTFIELD" |
| >width</CODE |
| ></TD |
| ><TD |
| > </TD |
| ><TD |
| >IN: Frame width for which the frame intervals are |
| enumerated.</TD |
| ></TR |
| ><TR |
| ><TD |
| >__u32</TD |
| ><TD |
| ><CODE |
| CLASS="STRUCTFIELD" |
| >height</CODE |
| ></TD |
| ><TD |
| > </TD |
| ><TD |
| >IN: Frame height for which the frame intervals are |
| enumerated.</TD |
| ></TR |
| ><TR |
| ><TD |
| >__u32</TD |
| ><TD |
| ><CODE |
| CLASS="STRUCTFIELD" |
| >type</CODE |
| ></TD |
| ><TD |
| > </TD |
| ><TD |
| >OUT: Frame interval type the device supports.</TD |
| ></TR |
| ><TR |
| ><TD |
| >union</TD |
| ><TD |
| > </TD |
| ><TD |
| > </TD |
| ><TD |
| >OUT: Frame interval with the given index.</TD |
| ></TR |
| ><TR |
| ><TD |
| > </TD |
| ><TD |
| >struct <A |
| HREF="r9288.htm#V4L2-FRACT" |
| >v4l2_fract</A |
| ></TD |
| ><TD |
| ><CODE |
| CLASS="STRUCTFIELD" |
| >discrete</CODE |
| ></TD |
| ><TD |
| >Frame interval [s].</TD |
| ></TR |
| ><TR |
| ><TD |
| > </TD |
| ><TD |
| >struct <A |
| HREF="r8724.htm#V4L2-FRMIVAL-STEPWISE" |
| >v4l2_frmival_stepwise</A |
| ></TD |
| ><TD |
| ><CODE |
| CLASS="STRUCTFIELD" |
| >stepwise</CODE |
| ></TD |
| ><TD |
| > </TD |
| ></TR |
| ><TR |
| ><TD |
| >__u32</TD |
| ><TD |
| ><CODE |
| CLASS="STRUCTFIELD" |
| >reserved[2]</CODE |
| ></TD |
| ><TD |
| > </TD |
| ><TD |
| >Reserved space for future use.</TD |
| ></TR |
| ></TBODY |
| ></TABLE |
| ></DIV |
| ></DIV |
| ><DIV |
| CLASS="REFSECT1" |
| ><A |
| NAME="AEN8902" |
| ></A |
| ><H2 |
| >Enums</H2 |
| ><DIV |
| CLASS="TABLE" |
| ><A |
| NAME="V4L2-FRMIVALTYPES" |
| ></A |
| ><P |
| ><B |
| >Table 3. enum <CODE |
| CLASS="STRUCTNAME" |
| >v4l2_frmivaltypes</CODE |
| ></B |
| ></P |
| ><TABLE |
| BORDER="0" |
| FRAME="void" |
| WIDTH="100%" |
| CLASS="CALSTABLE" |
| ><COL |
| WIDTH="38%" |
| TITLE="C1"><COL |
| WIDTH="12%" |
| TITLE="C2"><COL |
| WIDTH="50%" |
| TITLE="C3"><TBODY |
| VALIGN="TOP" |
| ><TR |
| ><TD |
| ><CODE |
| CLASS="CONSTANT" |
| >V4L2_FRMIVAL_TYPE_DISCRETE</CODE |
| ></TD |
| ><TD |
| >1</TD |
| ><TD |
| >Discrete frame interval.</TD |
| ></TR |
| ><TR |
| ><TD |
| ><CODE |
| CLASS="CONSTANT" |
| >V4L2_FRMIVAL_TYPE_CONTINUOUS</CODE |
| ></TD |
| ><TD |
| >2</TD |
| ><TD |
| >Continuous frame interval.</TD |
| ></TR |
| ><TR |
| ><TD |
| ><CODE |
| CLASS="CONSTANT" |
| >V4L2_FRMIVAL_TYPE_STEPWISE</CODE |
| ></TD |
| ><TD |
| >3</TD |
| ><TD |
| >Step-wise defined frame interval.</TD |
| ></TR |
| ></TBODY |
| ></TABLE |
| ></DIV |
| ></DIV |
| ><DIV |
| CLASS="REFSECT1" |
| ><A |
| NAME="AEN8928" |
| ></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 |
| >See the description section above for a list of return |
| values that <CODE |
| CLASS="VARNAME" |
| >errno</CODE |
| > can have.</P |
| ></DIV |
| ><DIV |
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