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