211 lines
5.4 KiB
ReStructuredText
211 lines
5.4 KiB
ReStructuredText
.. -*- coding: utf-8; mode: rst -*-
|
|
|
|
.. _VIDIOC_ENUM_FRAMESIZES:
|
|
|
|
****************************
|
|
ioctl VIDIOC_ENUM_FRAMESIZES
|
|
****************************
|
|
|
|
Name
|
|
====
|
|
|
|
VIDIOC_ENUM_FRAMESIZES - Enumerate frame sizes
|
|
|
|
|
|
Synopsis
|
|
========
|
|
|
|
.. c:function:: int ioctl( int fd, VIDIOC_ENUM_FRAMESIZES, struct v4l2_frmsizeenum *argp )
|
|
:name: VIDIOC_ENUM_FRAMESIZES
|
|
|
|
|
|
Arguments
|
|
=========
|
|
|
|
``fd``
|
|
File descriptor returned by :ref:`open() <func-open>`.
|
|
|
|
``argp``
|
|
Pointer to struct :c:type:`v4l2_frmsizeenum`
|
|
that contains an index and pixel format and receives a frame width
|
|
and height.
|
|
|
|
|
|
Description
|
|
===========
|
|
|
|
This ioctl allows applications to enumerate all frame sizes (i. e. width
|
|
and height in pixels) that the device supports for the given pixel
|
|
format.
|
|
|
|
The supported pixel formats can be obtained by using the
|
|
:ref:`VIDIOC_ENUM_FMT` function.
|
|
|
|
The return value and the content of the ``v4l2_frmsizeenum.type`` field
|
|
depend on the type of frame sizes 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_frmsizeenum.type`` field is set to
|
|
``V4L2_FRMSIZE_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_frmsizeenum.type`` field is set to
|
|
``V4L2_FRMSIZE_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_frmsizeenum.type``
|
|
field is set to ``V4L2_FRMSIZE_TYPE_CONTINUOUS`` by the driver. Of
|
|
the union only the ``stepwise`` member is valid and the
|
|
``step_width`` and ``step_height`` values are set to 1.
|
|
|
|
When the application calls the function with index zero, it must check
|
|
the ``type`` field to determine the type of frame size enumeration the
|
|
device supports. Only for the ``V4L2_FRMSIZE_TYPE_DISCRETE`` type does
|
|
it make sense to increase the index value to receive more frame sizes.
|
|
|
|
.. note::
|
|
|
|
The order in which the frame sizes are returned has no special
|
|
meaning. In particular does it not say anything about potential default
|
|
format sizes.
|
|
|
|
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 size enumeration.
|
|
|
|
|
|
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.
|
|
|
|
|
|
.. c:type:: v4l2_frmsize_discrete
|
|
|
|
.. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.7cm}|
|
|
|
|
.. flat-table:: struct v4l2_frmsize_discrete
|
|
:header-rows: 0
|
|
:stub-columns: 0
|
|
:widths: 1 1 2
|
|
|
|
* - __u32
|
|
- ``width``
|
|
- Width of the frame [pixel].
|
|
* - __u32
|
|
- ``height``
|
|
- Height of the frame [pixel].
|
|
|
|
|
|
|
|
.. c:type:: v4l2_frmsize_stepwise
|
|
|
|
.. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.7cm}|
|
|
|
|
.. flat-table:: struct v4l2_frmsize_stepwise
|
|
:header-rows: 0
|
|
:stub-columns: 0
|
|
:widths: 1 1 2
|
|
|
|
* - __u32
|
|
- ``min_width``
|
|
- Minimum frame width [pixel].
|
|
* - __u32
|
|
- ``max_width``
|
|
- Maximum frame width [pixel].
|
|
* - __u32
|
|
- ``step_width``
|
|
- Frame width step size [pixel].
|
|
* - __u32
|
|
- ``min_height``
|
|
- Minimum frame height [pixel].
|
|
* - __u32
|
|
- ``max_height``
|
|
- Maximum frame height [pixel].
|
|
* - __u32
|
|
- ``step_height``
|
|
- Frame height step size [pixel].
|
|
|
|
|
|
|
|
.. c:type:: v4l2_frmsizeenum
|
|
|
|
.. tabularcolumns:: |p{1.4cm}|p{5.9cm}|p{2.3cm}|p{8.0cm}|
|
|
|
|
.. flat-table:: struct v4l2_frmsizeenum
|
|
:header-rows: 0
|
|
:stub-columns: 0
|
|
|
|
* - __u32
|
|
- ``index``
|
|
-
|
|
- IN: Index of the given frame size in the enumeration.
|
|
* - __u32
|
|
- ``pixel_format``
|
|
-
|
|
- IN: Pixel format for which the frame sizes are enumerated.
|
|
* - __u32
|
|
- ``type``
|
|
-
|
|
- OUT: Frame size type the device supports.
|
|
* - union
|
|
-
|
|
-
|
|
- OUT: Frame size with the given index.
|
|
* -
|
|
- struct :c:type:`v4l2_frmsize_discrete`
|
|
- ``discrete``
|
|
-
|
|
* -
|
|
- struct :c:type:`v4l2_frmsize_stepwise`
|
|
- ``stepwise``
|
|
-
|
|
* - __u32
|
|
- ``reserved[2]``
|
|
-
|
|
- Reserved space for future use. Must be zeroed by drivers and
|
|
applications.
|
|
|
|
|
|
|
|
Enums
|
|
=====
|
|
|
|
|
|
.. c:type:: v4l2_frmsizetypes
|
|
|
|
.. tabularcolumns:: |p{6.6cm}|p{2.2cm}|p{8.7cm}|
|
|
|
|
.. flat-table:: enum v4l2_frmsizetypes
|
|
:header-rows: 0
|
|
:stub-columns: 0
|
|
:widths: 3 1 4
|
|
|
|
* - ``V4L2_FRMSIZE_TYPE_DISCRETE``
|
|
- 1
|
|
- Discrete frame size.
|
|
* - ``V4L2_FRMSIZE_TYPE_CONTINUOUS``
|
|
- 2
|
|
- Continuous frame size.
|
|
* - ``V4L2_FRMSIZE_TYPE_STEPWISE``
|
|
- 3
|
|
- Step-wise defined frame size.
|
|
|
|
|
|
Return Value
|
|
============
|
|
|
|
On success 0 is returned, on error -1 and the ``errno`` variable is set
|
|
appropriately. The generic error codes are described at the
|
|
:ref:`Generic Error Codes <gen-errors>` chapter.
|