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autogain_functions.h
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1 /*
2  * Functions for auto gain.
3  *
4  * Copyright (C) 2010-2011 Hans de Goede <[email protected]>
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  * You should have received a copy of the GNU General Public License
17  * along with this program; if not, write to the Free Software
18  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
19  */
20 
21 #ifdef WANT_REGULAR_AUTOGAIN
22 /* auto gain and exposure algorithm based on the knee algorithm described here:
23  http://ytse.tricolour.net/docs/LowLightOptimization.html
24 
25  Returns 0 if no changes were made, 1 if the gain and or exposure settings
26  where changed. */
27 static inline int auto_gain_n_exposure(
28  struct gspca_dev *gspca_dev,
29  int avg_lum,
30  int desired_avg_lum,
31  int deadzone,
32  int gain_knee,
33  int exposure_knee)
34 {
35  struct sd *sd = (struct sd *) gspca_dev;
36  int i, steps, gain, orig_gain, exposure, orig_exposure;
37  int retval = 0;
38 
39  orig_gain = gain = sd->ctrls[GAIN].val;
40  orig_exposure = exposure = sd->ctrls[EXPOSURE].val;
41 
42  /* If we are of a multiple of deadzone, do multiple steps to reach the
43  desired lumination fast (with the risc of a slight overshoot) */
44  steps = abs(desired_avg_lum - avg_lum) / deadzone;
45 
46  PDEBUG(D_FRAM, "autogain: lum: %d, desired: %d, steps: %d",
47  avg_lum, desired_avg_lum, steps);
48 
49  for (i = 0; i < steps; i++) {
50  if (avg_lum > desired_avg_lum) {
51  if (gain > gain_knee)
52  gain--;
53  else if (exposure > exposure_knee)
54  exposure--;
55  else if (gain > sd->ctrls[GAIN].def)
56  gain--;
57  else if (exposure > sd->ctrls[EXPOSURE].min)
58  exposure--;
59  else if (gain > sd->ctrls[GAIN].min)
60  gain--;
61  else
62  break;
63  } else {
64  if (gain < sd->ctrls[GAIN].def)
65  gain++;
66  else if (exposure < exposure_knee)
67  exposure++;
68  else if (gain < gain_knee)
69  gain++;
70  else if (exposure < sd->ctrls[EXPOSURE].max)
71  exposure++;
72  else if (gain < sd->ctrls[GAIN].max)
73  gain++;
74  else
75  break;
76  }
77  }
78 
79  if (gain != orig_gain) {
80  sd->ctrls[GAIN].val = gain;
81  setgain(gspca_dev);
82  retval = 1;
83  }
84  if (exposure != orig_exposure) {
85  sd->ctrls[EXPOSURE].val = exposure;
86  setexposure(gspca_dev);
87  retval = 1;
88  }
89 
90  if (retval)
91  PDEBUG(D_FRAM, "autogain: changed gain: %d, expo: %d",
92  gain, exposure);
93  return retval;
94 }
95 #endif
96 
97 #ifdef WANT_COARSE_EXPO_AUTOGAIN
98 /* Autogain + exposure algorithm for cameras with a coarse exposure control
99  (usually this means we can only control the clockdiv to change exposure)
100  As changing the clockdiv so that the fps drops from 30 to 15 fps for
101  example, will lead to a huge exposure change (it effectively doubles),
102  this algorithm normally tries to only adjust the gain (between 40 and
103  80 %) and if that does not help, only then changes exposure. This leads
104  to a much more stable image then using the knee algorithm which at
105  certain points of the knee graph will only try to adjust exposure,
106  which leads to oscilating as one exposure step is huge.
107 
108  Note this assumes that the sd struct for the cam in question has
109  exp_too_low_cnt and exp_too_high_cnt int members for use by this function.
110 
111  Returns 0 if no changes were made, 1 if the gain and or exposure settings
112  where changed. */
113 static inline int coarse_grained_expo_autogain(
114  struct gspca_dev *gspca_dev,
115  int avg_lum,
116  int desired_avg_lum,
117  int deadzone)
118 {
119  struct sd *sd = (struct sd *) gspca_dev;
120  int steps, gain, orig_gain, exposure, orig_exposure;
121  int gain_low, gain_high;
122  int retval = 0;
123 
124  orig_gain = gain = sd->ctrls[GAIN].val;
125  orig_exposure = exposure = sd->ctrls[EXPOSURE].val;
126 
127  gain_low = (sd->ctrls[GAIN].max - sd->ctrls[GAIN].min) / 5 * 2;
128  gain_low += sd->ctrls[GAIN].min;
129  gain_high = (sd->ctrls[GAIN].max - sd->ctrls[GAIN].min) / 5 * 4;
130  gain_high += sd->ctrls[GAIN].min;
131 
132  /* If we are of a multiple of deadzone, do multiple steps to reach the
133  desired lumination fast (with the risc of a slight overshoot) */
134  steps = (desired_avg_lum - avg_lum) / deadzone;
135 
136  PDEBUG(D_FRAM, "autogain: lum: %d, desired: %d, steps: %d",
137  avg_lum, desired_avg_lum, steps);
138 
139  if ((gain + steps) > gain_high &&
140  exposure < sd->ctrls[EXPOSURE].max) {
141  gain = gain_high;
142  sd->exp_too_low_cnt++;
143  sd->exp_too_high_cnt = 0;
144  } else if ((gain + steps) < gain_low &&
145  exposure > sd->ctrls[EXPOSURE].min) {
146  gain = gain_low;
147  sd->exp_too_high_cnt++;
148  sd->exp_too_low_cnt = 0;
149  } else {
150  gain += steps;
151  if (gain > sd->ctrls[GAIN].max)
152  gain = sd->ctrls[GAIN].max;
153  else if (gain < sd->ctrls[GAIN].min)
154  gain = sd->ctrls[GAIN].min;
155  sd->exp_too_high_cnt = 0;
156  sd->exp_too_low_cnt = 0;
157  }
158 
159  if (sd->exp_too_high_cnt > 3) {
160  exposure--;
161  sd->exp_too_high_cnt = 0;
162  } else if (sd->exp_too_low_cnt > 3) {
163  exposure++;
164  sd->exp_too_low_cnt = 0;
165  }
166 
167  if (gain != orig_gain) {
168  sd->ctrls[GAIN].val = gain;
169  setgain(gspca_dev);
170  retval = 1;
171  }
172  if (exposure != orig_exposure) {
173  sd->ctrls[EXPOSURE].val = exposure;
174  setexposure(gspca_dev);
175  retval = 1;
176  }
177 
178  if (retval)
179  PDEBUG(D_FRAM, "autogain: changed gain: %d, expo: %d",
180  gain, exposure);
181  return retval;
182 }
183 #endif