drivers/media/usb/gspca/autogain_functions.c

   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  * 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 #include "gspca.h"
  21
  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 int gspca_expo_autogain(
  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         s32 gain, orig_gain, exposure, orig_exposure;
  36         int i, steps, retval = 0;
  37
  38         if (v4l2_ctrl_g_ctrl(gspca_dev->autogain) == 0)
  39                 return 0;
  40
  41         orig_gain = gain = v4l2_ctrl_g_ctrl(gspca_dev->gain);
  42         orig_exposure = exposure = v4l2_ctrl_g_ctrl(gspca_dev->exposure);
  43
  44         /* If we are of a multiple of deadzone, do multiple steps to reach the
  45            desired lumination fast (with the risc of a slight overshoot) */
  46         steps = abs(desired_avg_lum - avg_lum) / deadzone;
  47
  48         PDEBUG(D_FRAM, "autogain: lum: %d, desired: %d, steps: %d",
  49                 avg_lum, desired_avg_lum, steps);
  50
  51         for (i = 0; i < steps; i++) {
  52                 if (avg_lum > desired_avg_lum) {
  53                         if (gain > gain_knee)
  54                                 gain--;
  55                         else if (exposure > exposure_knee)
  56                                 exposure--;
  57                         else if (gain > gspca_dev->gain->default_value)
  58                                 gain--;
  59                         else if (exposure > gspca_dev->exposure->minimum)
  60                                 exposure--;
  61                         else if (gain > gspca_dev->gain->minimum)
  62                                 gain--;
  63                         else
  64                                 break;
  65                 } else {
  66                         if (gain < gspca_dev->gain->default_value)
  67                                 gain++;
  68                         else if (exposure < exposure_knee)
  69                                 exposure++;
  70                         else if (gain < gain_knee)
  71                                 gain++;
  72                         else if (exposure < gspca_dev->exposure->maximum)
  73                                 exposure++;
  74                         else if (gain < gspca_dev->gain->maximum)
  75                                 gain++;
  76                         else
  77                                 break;
  78                 }
  79         }
  80
  81         if (gain != orig_gain) {
  82                 v4l2_ctrl_s_ctrl(gspca_dev->gain, gain);
  83                 retval = 1;
  84         }
  85         if (exposure != orig_exposure) {
  86                 v4l2_ctrl_s_ctrl(gspca_dev->exposure, exposure);
  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 EXPORT_SYMBOL(gspca_expo_autogain);
  96
  97 /* Autogain + exposure algorithm for cameras with a coarse exposure control
  98    (usually this means we can only control the clockdiv to change exposure)
  99    As changing the clockdiv so that the fps drops from 30 to 15 fps for
 100    example, will lead to a huge exposure change (it effectively doubles),
 101    this algorithm normally tries to only adjust the gain (between 40 and
 102    80 %) and if that does not help, only then changes exposure. This leads
 103    to a much more stable image then using the knee algorithm which at
 104    certain points of the knee graph will only try to adjust exposure,
 105    which leads to oscilating as one exposure step is huge.
 106
 107    Returns 0 if no changes were made, 1 if the gain and or exposure settings
 108    where changed. */
 109 int gspca_coarse_grained_expo_autogain(
 110                         struct gspca_dev *gspca_dev,
 111                         int avg_lum,
 112                         int desired_avg_lum,
 113                         int deadzone)
 114 {
 115         s32 gain_low, gain_high, gain, orig_gain, exposure, orig_exposure;
 116         int steps, retval = 0;
 117
 118         if (v4l2_ctrl_g_ctrl(gspca_dev->autogain) == 0)
 119                 return 0;
 120
 121         orig_gain = gain = v4l2_ctrl_g_ctrl(gspca_dev->gain);
 122         orig_exposure = exposure = v4l2_ctrl_g_ctrl(gspca_dev->exposure);
 123
 124         gain_low  = (gspca_dev->gain->maximum - gspca_dev->gain->minimum) /
 125                     5 * 2 + gspca_dev->gain->minimum;
 126         gain_high = (gspca_dev->gain->maximum - gspca_dev->gain->minimum) /
 127                     5 * 4 + gspca_dev->gain->minimum;
 128
 129         /* If we are of a multiple of deadzone, do multiple steps to reach the
 130            desired lumination fast (with the risc of a slight overshoot) */
 131         steps = (desired_avg_lum - avg_lum) / deadzone;
 132
 133         PDEBUG(D_FRAM, "autogain: lum: %d, desired: %d, steps: %d",
 134                 avg_lum, desired_avg_lum, steps);
 135
 136         if ((gain + steps) > gain_high &&
 137             exposure < gspca_dev->exposure->maximum) {
 138                 gain = gain_high;
 139                 gspca_dev->exp_too_low_cnt++;
 140                 gspca_dev->exp_too_high_cnt = 0;
 141         } else if ((gain + steps) < gain_low &&
 142                    exposure > gspca_dev->exposure->minimum) {
 143                 gain = gain_low;
 144                 gspca_dev->exp_too_high_cnt++;
 145                 gspca_dev->exp_too_low_cnt = 0;
 146         } else {
 147                 gain += steps;
 148                 if (gain > gspca_dev->gain->maximum)
 149                         gain = gspca_dev->gain->maximum;
 150                 else if (gain < gspca_dev->gain->minimum)
 151                         gain = gspca_dev->gain->minimum;
 152                 gspca_dev->exp_too_high_cnt = 0;
 153                 gspca_dev->exp_too_low_cnt = 0;
 154         }
 155
 156         if (gspca_dev->exp_too_high_cnt > 3) {
 157                 exposure--;
 158                 gspca_dev->exp_too_high_cnt = 0;
 159         } else if (gspca_dev->exp_too_low_cnt > 3) {
 160                 exposure++;
 161                 gspca_dev->exp_too_low_cnt = 0;
 162         }
 163
 164         if (gain != orig_gain) {
 165                 v4l2_ctrl_s_ctrl(gspca_dev->gain, gain);
 166                 retval = 1;
 167         }
 168         if (exposure != orig_exposure) {
 169                 v4l2_ctrl_s_ctrl(gspca_dev->exposure, exposure);
 170                 retval = 1;
 171         }
 172
 173         if (retval)
 174                 PDEBUG(D_FRAM, "autogain: changed gain: %d, expo: %d",
 175                         gain, exposure);
 176         return retval;
 177 }
 178 EXPORT_SYMBOL(gspca_coarse_grained_expo_autogain);