1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3 * Functions for auto gain.
4 *
5 * Copyright (C) 2010-2012 Hans de Goede <hdegoede@redhat.com>
6 */
7 #include "gspca.h"
8
9 /* auto gain and exposure algorithm based on the knee algorithm described here:
10 http://ytse.tricolour.net/docs/LowLightOptimization.html
11
12 Returns 0 if no changes were made, 1 if the gain and or exposure settings
13 where changed. */
gspca_expo_autogain(struct gspca_dev * gspca_dev,int avg_lum,int desired_avg_lum,int deadzone,int gain_knee,int exposure_knee)14 int gspca_expo_autogain(
15 struct gspca_dev *gspca_dev,
16 int avg_lum,
17 int desired_avg_lum,
18 int deadzone,
19 int gain_knee,
20 int exposure_knee)
21 {
22 s32 gain, orig_gain, exposure, orig_exposure;
23 int i, steps, retval = 0;
24
25 if (v4l2_ctrl_g_ctrl(gspca_dev->autogain) == 0)
26 return 0;
27
28 orig_gain = gain = v4l2_ctrl_g_ctrl(gspca_dev->gain);
29 orig_exposure = exposure = v4l2_ctrl_g_ctrl(gspca_dev->exposure);
30
31 /* If we are of a multiple of deadzone, do multiple steps to reach the
32 desired lumination fast (with the risc of a slight overshoot) */
33 steps = abs(desired_avg_lum - avg_lum) / deadzone;
34
35 gspca_dbg(gspca_dev, D_FRAM, "autogain: lum: %d, desired: %d, steps: %d\n",
36 avg_lum, desired_avg_lum, steps);
37
38 for (i = 0; i < steps; i++) {
39 if (avg_lum > desired_avg_lum) {
40 if (gain > gain_knee)
41 gain--;
42 else if (exposure > exposure_knee)
43 exposure--;
44 else if (gain > gspca_dev->gain->default_value)
45 gain--;
46 else if (exposure > gspca_dev->exposure->minimum)
47 exposure--;
48 else if (gain > gspca_dev->gain->minimum)
49 gain--;
50 else
51 break;
52 } else {
53 if (gain < gspca_dev->gain->default_value)
54 gain++;
55 else if (exposure < exposure_knee)
56 exposure++;
57 else if (gain < gain_knee)
58 gain++;
59 else if (exposure < gspca_dev->exposure->maximum)
60 exposure++;
61 else if (gain < gspca_dev->gain->maximum)
62 gain++;
63 else
64 break;
65 }
66 }
67
68 if (gain != orig_gain) {
69 v4l2_ctrl_s_ctrl(gspca_dev->gain, gain);
70 retval = 1;
71 }
72 if (exposure != orig_exposure) {
73 v4l2_ctrl_s_ctrl(gspca_dev->exposure, exposure);
74 retval = 1;
75 }
76
77 if (retval)
78 gspca_dbg(gspca_dev, D_FRAM, "autogain: changed gain: %d, expo: %d\n",
79 gain, exposure);
80 return retval;
81 }
82 EXPORT_SYMBOL(gspca_expo_autogain);
83
84 /* Autogain + exposure algorithm for cameras with a coarse exposure control
85 (usually this means we can only control the clockdiv to change exposure)
86 As changing the clockdiv so that the fps drops from 30 to 15 fps for
87 example, will lead to a huge exposure change (it effectively doubles),
88 this algorithm normally tries to only adjust the gain (between 40 and
89 80 %) and if that does not help, only then changes exposure. This leads
90 to a much more stable image then using the knee algorithm which at
91 certain points of the knee graph will only try to adjust exposure,
92 which leads to oscillating as one exposure step is huge.
93
94 Returns 0 if no changes were made, 1 if the gain and or exposure settings
95 where changed. */
gspca_coarse_grained_expo_autogain(struct gspca_dev * gspca_dev,int avg_lum,int desired_avg_lum,int deadzone)96 int gspca_coarse_grained_expo_autogain(
97 struct gspca_dev *gspca_dev,
98 int avg_lum,
99 int desired_avg_lum,
100 int deadzone)
101 {
102 s32 gain_low, gain_high, gain, orig_gain, exposure, orig_exposure;
103 int steps, retval = 0;
104
105 if (v4l2_ctrl_g_ctrl(gspca_dev->autogain) == 0)
106 return 0;
107
108 orig_gain = gain = v4l2_ctrl_g_ctrl(gspca_dev->gain);
109 orig_exposure = exposure = v4l2_ctrl_g_ctrl(gspca_dev->exposure);
110
111 gain_low = (s32)(gspca_dev->gain->maximum - gspca_dev->gain->minimum) /
112 5 * 2 + gspca_dev->gain->minimum;
113 gain_high = (s32)(gspca_dev->gain->maximum - gspca_dev->gain->minimum) /
114 5 * 4 + gspca_dev->gain->minimum;
115
116 /* If we are of a multiple of deadzone, do multiple steps to reach the
117 desired lumination fast (with the risc of a slight overshoot) */
118 steps = (desired_avg_lum - avg_lum) / deadzone;
119
120 gspca_dbg(gspca_dev, D_FRAM, "autogain: lum: %d, desired: %d, steps: %d\n",
121 avg_lum, desired_avg_lum, steps);
122
123 if ((gain + steps) > gain_high &&
124 exposure < gspca_dev->exposure->maximum) {
125 gain = gain_high;
126 gspca_dev->exp_too_low_cnt++;
127 gspca_dev->exp_too_high_cnt = 0;
128 } else if ((gain + steps) < gain_low &&
129 exposure > gspca_dev->exposure->minimum) {
130 gain = gain_low;
131 gspca_dev->exp_too_high_cnt++;
132 gspca_dev->exp_too_low_cnt = 0;
133 } else {
134 gain += steps;
135 if (gain > gspca_dev->gain->maximum)
136 gain = gspca_dev->gain->maximum;
137 else if (gain < gspca_dev->gain->minimum)
138 gain = gspca_dev->gain->minimum;
139 gspca_dev->exp_too_high_cnt = 0;
140 gspca_dev->exp_too_low_cnt = 0;
141 }
142
143 if (gspca_dev->exp_too_high_cnt > 3) {
144 exposure--;
145 gspca_dev->exp_too_high_cnt = 0;
146 } else if (gspca_dev->exp_too_low_cnt > 3) {
147 exposure++;
148 gspca_dev->exp_too_low_cnt = 0;
149 }
150
151 if (gain != orig_gain) {
152 v4l2_ctrl_s_ctrl(gspca_dev->gain, gain);
153 retval = 1;
154 }
155 if (exposure != orig_exposure) {
156 v4l2_ctrl_s_ctrl(gspca_dev->exposure, exposure);
157 retval = 1;
158 }
159
160 if (retval)
161 gspca_dbg(gspca_dev, D_FRAM, "autogain: changed gain: %d, expo: %d\n",
162 gain, exposure);
163 return retval;
164 }
165 EXPORT_SYMBOL(gspca_coarse_grained_expo_autogain);
166