drivers/media/usb/gspca/autogain_functions.c

   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. */
  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. */
  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);