From 849369d6c66d3054688672f97d31fceb8e8230fb Mon Sep 17 00:00:00 2001 From: root Date: Fri, 25 Dec 2015 04:40:36 +0000 Subject: initial_commit --- .../DocBook/v4l/vidioc-enum-frameintervals.xml | 270 +++++++++++++++++++++ 1 file changed, 270 insertions(+) create mode 100644 Documentation/DocBook/v4l/vidioc-enum-frameintervals.xml (limited to 'Documentation/DocBook/v4l/vidioc-enum-frameintervals.xml') diff --git a/Documentation/DocBook/v4l/vidioc-enum-frameintervals.xml b/Documentation/DocBook/v4l/vidioc-enum-frameintervals.xml new file mode 100644 index 00000000..3c216e11 --- /dev/null +++ b/Documentation/DocBook/v4l/vidioc-enum-frameintervals.xml @@ -0,0 +1,270 @@ + + + + ioctl VIDIOC_ENUM_FRAMEINTERVALS + &manvol; + + + + VIDIOC_ENUM_FRAMEINTERVALS + Enumerate frame intervals + + + + + + int ioctl + int fd + int request + struct v4l2_frmivalenum *argp + + + + + + Arguments + + + + fd + + &fd; + + + + request + + VIDIOC_ENUM_FRAMEINTERVALS + + + + argp + + Pointer to a &v4l2-frmivalenum; structure that +contains a pixel format and size and receives a frame interval. + + + + + + + Description + + This ioctl allows applications to enumerate all frame +intervals that the device supports for the given pixel format and +frame size. + The supported pixel formats and frame sizes can be obtained +by using the &VIDIOC-ENUM-FMT; and &VIDIOC-ENUM-FRAMESIZES; +functions. + The return value and the content of the +v4l2_frmivalenum.type field depend on the +type of frame intervals the device supports. Here are the semantics of +the function for the different cases: + + + Discrete: 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 +EINVAL 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. + + + Step-wise: The function +returns success if the given index value is zero and +EINVAL for any other index value. The +v4l2_frmivalenum.type field is set to +V4L2_FRMIVAL_TYPE_STEPWISE by the driver. Of the +union only the stepwise member is +valid. + + + Continuous: This is a +special case of the step-wise type above. The function returns success +if the given index value is zero and EINVAL for +any other index value. The +v4l2_frmivalenum.type field is set to +V4L2_FRMIVAL_TYPE_CONTINUOUS by the driver. Of +the union only the stepwise member is valid +and the step value is set to 1. + + + + When the application calls the function with index zero, it +must check the type field to determine the +type of frame interval enumeration the device supports. Only for the +V4L2_FRMIVAL_TYPE_DISCRETE type does it make +sense to increase the index value to receive more frame +intervals. + 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. + 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. + + + + Notes + + + + Frame intervals and frame +rates: The V4L2 API uses frame intervals instead of frame +rates. Given the frame interval the frame rate can be computed as +follows:frame_rate = 1 / frame_interval + + + + + + + Structs + + In the structs below, IN denotes a +value that has to be filled in by the application, +OUT denotes values that the driver fills in. The +application should zero out all members except for the +IN fields. + + + struct <structname>v4l2_frmival_stepwise</structname> + + &cs-str; + + + &v4l2-fract; + min + Minimum frame interval [s]. + + + &v4l2-fract; + max + Maximum frame interval [s]. + + + &v4l2-fract; + step + Frame interval step size [s]. + + + +
+ + + struct <structname>v4l2_frmivalenum</structname> + + + + + + + + __u32 + index + + IN: Index of the given frame interval in the +enumeration. + + + __u32 + pixel_format + + IN: Pixel format for which the frame intervals are +enumerated. + + + __u32 + width + + IN: Frame width for which the frame intervals are +enumerated. + + + __u32 + height + + IN: Frame height for which the frame intervals are +enumerated. + + + __u32 + type + + OUT: Frame interval type the device supports. + + + union + + + OUT: Frame interval with the given index. + + + + &v4l2-fract; + discrete + Frame interval [s]. + + + + &v4l2-frmival-stepwise; + stepwise + + + + __u32 + reserved[2] + + Reserved space for future use. + + + +
+ + + + Enums + + + enum <structname>v4l2_frmivaltypes</structname> + + &cs-def; + + + V4L2_FRMIVAL_TYPE_DISCRETE + 1 + Discrete frame interval. + + + V4L2_FRMIVAL_TYPE_CONTINUOUS + 2 + Continuous frame interval. + + + V4L2_FRMIVAL_TYPE_STEPWISE + 3 + Step-wise defined frame interval. + + + +
+ + + + &return-value; + + See the description section above for a list of return +values that errno can have. + + + + + -- cgit v1.2.3