Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
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1.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
2.. c:namespace:: V4L
3
4.. _image-source-controls:
5
6******************************
7Image Source Control Reference
8******************************
9
10The Image Source control class is intended for low-level control of
11image source devices such as image sensors. The devices feature an
12analogue to digital converter and a bus transmitter to transmit the
13image data out of the device.
14
15
16.. _image-source-control-id:
17
18Image Source Control IDs
19========================
20
21``V4L2_CID_IMAGE_SOURCE_CLASS (class)``
22 The IMAGE_SOURCE class descriptor.
23
24``V4L2_CID_VBLANK (integer)``
25 Vertical blanking. The idle period after every frame during which no
26 image data is produced. The unit of vertical blanking is a line.
27 Every line has length of the image width plus horizontal blanking at
28 the pixel rate defined by ``V4L2_CID_PIXEL_RATE`` control in the
29 same sub-device.
30
31``V4L2_CID_HBLANK (integer)``
32 Horizontal blanking. The idle period after every line of image data
33 during which no image data is produced. The unit of horizontal
34 blanking is pixels.
35
36``V4L2_CID_ANALOGUE_GAIN (integer)``
37 Analogue gain is gain affecting all colour components in the pixel
38 matrix. The gain operation is performed in the analogue domain
39 before A/D conversion.
40
41``V4L2_CID_TEST_PATTERN_RED (integer)``
42 Test pattern red colour component.
43
44``V4L2_CID_TEST_PATTERN_GREENR (integer)``
45 Test pattern green (next to red) colour component.
46
47``V4L2_CID_TEST_PATTERN_BLUE (integer)``
48 Test pattern blue colour component.
49
50``V4L2_CID_TEST_PATTERN_GREENB (integer)``
51 Test pattern green (next to blue) colour component.
52
53``V4L2_CID_UNIT_CELL_SIZE (struct)``
54 This control returns the unit cell size in nanometers. The struct
55 :c:type:`v4l2_area` provides the width and the height in separate
56 fields to take into consideration asymmetric pixels.
57 This control does not take into consideration any possible hardware
58 binning.
59 The unit cell consists of the whole area of the pixel, sensitive and
60 non-sensitive.
61 This control is required for automatic calibration of sensors/cameras.
62
63.. c:type:: v4l2_area
64
65.. flat-table:: struct v4l2_area
66 :header-rows: 0
67 :stub-columns: 0
68 :widths: 1 1 2
69
70 * - __u32
71 - ``width``
72 - Width of the area.
73 * - __u32
74 - ``height``
75 - Height of the area.
76
77``V4L2_CID_NOTIFY_GAINS (integer array)``
78 The sensor is notified what gains will be applied to the different
79 colour channels by subsequent processing (such as by an ISP). The
80 sensor is merely informed of these values in case it performs
81 processing that requires them, but it does not apply them itself to
82 the output pixels.
83
84 Currently it is defined only for Bayer sensors, and is an array
85 control taking 4 gain values, being the gains for each of the
86 Bayer channels. The gains are always in the order B, Gb, Gr and R,
87 irrespective of the exact Bayer order of the sensor itself.
88
89 The use of an array allows this control to be extended to sensors
90 with, for example, non-Bayer CFAs (colour filter arrays).
91
92 The units for the gain values are linear, with the default value
93 representing a gain of exactly 1.0. For example, if this default value
94 is reported as being (say) 128, then a value of 192 would represent
95 a gain of exactly 1.5.