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.. Permission is granted to copy, distribute and/or modify this
.. document under the terms of the GNU Free Documentation License,
.. Version 1.1 or any later version published by the Free Software
.. Foundation, with no Invariant Sections, no Front-Cover Texts
.. and no Back-Cover Texts. A copy of the license is included at
.. Documentation/media/uapi/fdl-appendix.rst.
.. TODO: replace it to GFDL-1.1-or-later WITH no-invariant-sections
.. _image-process-controls:
Image Process Control Reference
The Image Process control class is intended for low-level control of
image processing functions. Unlike ``V4L2_CID_IMAGE_SOURCE_CLASS``, the
controls in this class affect processing the image, and do not control
capturing of it.
.. _image-process-control-id:
Image Process Control IDs
The IMAGE_PROC class descriptor.
``V4L2_CID_LINK_FREQ (integer menu)``
Data bus frequency. Together with the media bus pixel code, bus type
(clock cycles per sample), the data bus frequency defines the pixel
rate (``V4L2_CID_PIXEL_RATE``) in the pixel array (or possibly
elsewhere, if the device is not an image sensor). The frame rate can
be calculated from the pixel clock, image width and height and
horizontal and vertical blanking. While the pixel rate control may
be defined elsewhere than in the subdev containing the pixel array,
the frame rate cannot be obtained from that information. This is
because only on the pixel array it can be assumed that the vertical
and horizontal blanking information is exact: no other blanking is
allowed in the pixel array. The selection of frame rate is performed
by selecting the desired horizontal and vertical blanking. The unit
of this control is Hz.
``V4L2_CID_PIXEL_RATE (64-bit integer)``
Pixel rate in the source pads of the subdev. This control is
read-only and its unit is pixels / second.
``V4L2_CID_TEST_PATTERN (menu)``
Some capture/display/sensor devices have the capability to generate
test pattern images. These hardware specific test patterns can be
used to test if a device is working properly.
The video deinterlacing mode (such as Bob, Weave, ...). The menu items are
driver specific and are documented in :ref:`v4l-drivers`.
``V4L2_CID_DIGITAL_GAIN (integer)``
Digital gain is the value by which all colour components
are multiplied by. Typically the digital gain applied is the
control value divided by e.g. 0x100, meaning that to get no
digital gain the control value needs to be 0x100. The no-gain
configuration is also typically the default.