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 #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. */
  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 oscillating 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. */
 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);