1 /*
2 * Functions for auto gain.
3 *
4 * Copyright (C) 2010-2012 Hans de Goede <hdegoede@redhat.com>
5 *
6 * This program is free software; you can redistribute it and/or modify
7 * it under the terms of the GNU General Public License as published by
8 * the Free Software Foundation; either version 2 of the License, or
9 * (at your option) any later version.
10 *
11 * This program is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 * GNU General Public License for more details.
15 */
16 #include "gspca.h"
17
18 /* auto gain and exposure algorithm based on the knee algorithm described here:
19 http://ytse.tricolour.net/docs/LowLightOptimization.html
20
21 Returns 0 if no changes were made, 1 if the gain and or exposure settings
22 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)23 int gspca_expo_autogain(
24 struct gspca_dev *gspca_dev,
25 int avg_lum,
26 int desired_avg_lum,
27 int deadzone,
28 int gain_knee,
29 int exposure_knee)
30 {
31 s32 gain, orig_gain, exposure, orig_exposure;
32 int i, steps, retval = 0;
33
34 if (v4l2_ctrl_g_ctrl(gspca_dev->autogain) == 0)
35 return 0;
36
37 orig_gain = gain = v4l2_ctrl_g_ctrl(gspca_dev->gain);
38 orig_exposure = exposure = v4l2_ctrl_g_ctrl(gspca_dev->exposure);
39
40 /* If we are of a multiple of deadzone, do multiple steps to reach the
41 desired lumination fast (with the risc of a slight overshoot) */
42 steps = abs(desired_avg_lum - avg_lum) / deadzone;
43
44 gspca_dbg(gspca_dev, D_FRAM, "autogain: lum: %d, desired: %d, steps: %d\n",
45 avg_lum, desired_avg_lum, steps);
46
47 for (i = 0; i < steps; i++) {
48 if (avg_lum > desired_avg_lum) {
49 if (gain > gain_knee)
50 gain--;
51 else if (exposure > exposure_knee)
52 exposure--;
53 else if (gain > gspca_dev->gain->default_value)
54 gain--;
55 else if (exposure > gspca_dev->exposure->minimum)
56 exposure--;
57 else if (gain > gspca_dev->gain->minimum)
58 gain--;
59 else
60 break;
61 } else {
62 if (gain < gspca_dev->gain->default_value)
63 gain++;
64 else if (exposure < exposure_knee)
65 exposure++;
66 else if (gain < gain_knee)
67 gain++;
68 else if (exposure < gspca_dev->exposure->maximum)
69 exposure++;
70 else if (gain < gspca_dev->gain->maximum)
71 gain++;
72 else
73 break;
74 }
75 }
76
77 if (gain != orig_gain) {
78 v4l2_ctrl_s_ctrl(gspca_dev->gain, gain);
79 retval = 1;
80 }
81 if (exposure != orig_exposure) {
82 v4l2_ctrl_s_ctrl(gspca_dev->exposure, exposure);
83 retval = 1;
84 }
85
86 if (retval)
87 gspca_dbg(gspca_dev, D_FRAM, "autogain: changed gain: %d, expo: %d\n",
88 gain, exposure);
89 return retval;
90 }
91 EXPORT_SYMBOL(gspca_expo_autogain);
92
93 /* Autogain + exposure algorithm for cameras with a coarse exposure control
94 (usually this means we can only control the clockdiv to change exposure)
95 As changing the clockdiv so that the fps drops from 30 to 15 fps for
96 example, will lead to a huge exposure change (it effectively doubles),
97 this algorithm normally tries to only adjust the gain (between 40 and
98 80 %) and if that does not help, only then changes exposure. This leads
99 to a much more stable image then using the knee algorithm which at
100 certain points of the knee graph will only try to adjust exposure,
101 which leads to oscilating as one exposure step is huge.
102
103 Returns 0 if no changes were made, 1 if the gain and or exposure settings
104 where changed. */
gspca_coarse_grained_expo_autogain(struct gspca_dev * gspca_dev,int avg_lum,int desired_avg_lum,int deadzone)105 int gspca_coarse_grained_expo_autogain(
106 struct gspca_dev *gspca_dev,
107 int avg_lum,
108 int desired_avg_lum,
109 int deadzone)
110 {
111 s32 gain_low, gain_high, gain, orig_gain, exposure, orig_exposure;
112 int steps, retval = 0;
113
114 if (v4l2_ctrl_g_ctrl(gspca_dev->autogain) == 0)
115 return 0;
116
117 orig_gain = gain = v4l2_ctrl_g_ctrl(gspca_dev->gain);
118 orig_exposure = exposure = v4l2_ctrl_g_ctrl(gspca_dev->exposure);
119
120 gain_low = (s32)(gspca_dev->gain->maximum - gspca_dev->gain->minimum) /
121 5 * 2 + gspca_dev->gain->minimum;
122 gain_high = (s32)(gspca_dev->gain->maximum - gspca_dev->gain->minimum) /
123 5 * 4 + gspca_dev->gain->minimum;
124
125 /* If we are of a multiple of deadzone, do multiple steps to reach the
126 desired lumination fast (with the risc of a slight overshoot) */
127 steps = (desired_avg_lum - avg_lum) / deadzone;
128
129 gspca_dbg(gspca_dev, D_FRAM, "autogain: lum: %d, desired: %d, steps: %d\n",
130 avg_lum, desired_avg_lum, steps);
131
132 if ((gain + steps) > gain_high &&
133 exposure < gspca_dev->exposure->maximum) {
134 gain = gain_high;
135 gspca_dev->exp_too_low_cnt++;
136 gspca_dev->exp_too_high_cnt = 0;
137 } else if ((gain + steps) < gain_low &&
138 exposure > gspca_dev->exposure->minimum) {
139 gain = gain_low;
140 gspca_dev->exp_too_high_cnt++;
141 gspca_dev->exp_too_low_cnt = 0;
142 } else {
143 gain += steps;
144 if (gain > gspca_dev->gain->maximum)
145 gain = gspca_dev->gain->maximum;
146 else if (gain < gspca_dev->gain->minimum)
147 gain = gspca_dev->gain->minimum;
148 gspca_dev->exp_too_high_cnt = 0;
149 gspca_dev->exp_too_low_cnt = 0;
150 }
151
152 if (gspca_dev->exp_too_high_cnt > 3) {
153 exposure--;
154 gspca_dev->exp_too_high_cnt = 0;
155 } else if (gspca_dev->exp_too_low_cnt > 3) {
156 exposure++;
157 gspca_dev->exp_too_low_cnt = 0;
158 }
159
160 if (gain != orig_gain) {
161 v4l2_ctrl_s_ctrl(gspca_dev->gain, gain);
162 retval = 1;
163 }
164 if (exposure != orig_exposure) {
165 v4l2_ctrl_s_ctrl(gspca_dev->exposure, exposure);
166 retval = 1;
167 }
168
169 if (retval)
170 gspca_dbg(gspca_dev, D_FRAM, "autogain: changed gain: %d, expo: %d\n",
171 gain, exposure);
172 return retval;
173 }
174 EXPORT_SYMBOL(gspca_coarse_grained_expo_autogain);
175