26984b0995
Some sensors only allow controlling the exposure by changing the clockdiv, which means that exposure takes pretty large jumps (for example when going from a div of 1 to 2, the exposure doubles). Use 2 different entries in the controls array for these 2 different types of exposure (always disabling one), and; Add a new autogain algorithm for the coarse exposure case, which normally changes the gain setting, only touching the exposure setting if the desired luminance cannot be reached with gain, and after an exposure change once more first tries gain, etc. Thus avoiding exposure changes, and the resulting oscilation because of the huge steps these exposure controls take. Signed-off-by: Hans de Goede <hdegoede@redhat.com> Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
116 lines
4 KiB
C
116 lines
4 KiB
C
/*
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* Auto gain algorithm for camera's with a coarse exposure control
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*
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* Copyright (C) 2010 Hans de Goede <hdegoede@redhat.com>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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*/
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/* Autogain + exposure algorithm for cameras with a coarse exposure control
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(usually this means we can only control the clockdiv to change exposure)
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As changing the clockdiv so that the fps drops from 30 to 15 fps for
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example, will lead to a huge exposure change (it effectively doubles),
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this algorithm normally tries to only adjust the gain (between 40 and
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80 %) and if that does not help, only then changes exposure. This leads
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to a much more stable image then using the knee algorithm which at
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certain points of the knee graph will only try to adjust exposure,
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which leads to oscilating as one exposure step is huge.
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Note this assumes that the sd struct for the cam in question has
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exp_too_high_cnt and exp_too_high_cnt int members for use by this function.
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Returns 0 if no changes were made, 1 if the gain and or exposure settings
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where changed. */
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static int gspca_coarse_grained_expo_autogain(struct gspca_dev *gspca_dev,
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int avg_lum, int desired_avg_lum, int deadzone)
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{
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int i, steps, gain, orig_gain, exposure, orig_exposure;
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int gain_low, gain_high;
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const struct ctrl *gain_ctrl = NULL;
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const struct ctrl *exposure_ctrl = NULL;
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struct sd *sd = (struct sd *) gspca_dev;
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int retval = 0;
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for (i = 0; i < gspca_dev->sd_desc->nctrls; i++) {
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if (gspca_dev->ctrl_dis & (1 << i))
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continue;
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if (gspca_dev->sd_desc->ctrls[i].qctrl.id == V4L2_CID_GAIN)
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gain_ctrl = &gspca_dev->sd_desc->ctrls[i];
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if (gspca_dev->sd_desc->ctrls[i].qctrl.id == V4L2_CID_EXPOSURE)
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exposure_ctrl = &gspca_dev->sd_desc->ctrls[i];
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}
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if (!gain_ctrl || !exposure_ctrl) {
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PDEBUG(D_ERR, "Error: gspca_coarse_grained_expo_autogain "
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"called on cam without gain or exposure");
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return 0;
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}
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if (gain_ctrl->get(gspca_dev, &gain) ||
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exposure_ctrl->get(gspca_dev, &exposure))
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return 0;
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orig_gain = gain;
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orig_exposure = exposure;
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gain_low =
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(gain_ctrl->qctrl.maximum - gain_ctrl->qctrl.minimum) / 5 * 2;
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gain_low += gain_ctrl->qctrl.minimum;
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gain_high =
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(gain_ctrl->qctrl.maximum - gain_ctrl->qctrl.minimum) / 5 * 4;
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gain_high += gain_ctrl->qctrl.minimum;
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/* If we are of a multiple of deadzone, do multiple steps to reach the
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desired lumination fast (with the risc of a slight overshoot) */
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steps = (desired_avg_lum - avg_lum) / deadzone;
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PDEBUG(D_FRAM, "autogain: lum: %d, desired: %d, steps: %d",
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avg_lum, desired_avg_lum, steps);
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if ((gain + steps) > gain_high &&
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sd->exposure < exposure_ctrl->qctrl.maximum) {
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gain = gain_high;
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sd->exp_too_low_cnt++;
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} else if ((gain + steps) < gain_low &&
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sd->exposure > exposure_ctrl->qctrl.minimum) {
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gain = gain_low;
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sd->exp_too_high_cnt++;
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} else {
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gain += steps;
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if (gain > gain_ctrl->qctrl.maximum)
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gain = gain_ctrl->qctrl.maximum;
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else if (gain < gain_ctrl->qctrl.minimum)
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gain = gain_ctrl->qctrl.minimum;
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sd->exp_too_high_cnt = 0;
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sd->exp_too_low_cnt = 0;
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}
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if (sd->exp_too_high_cnt > 3) {
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exposure--;
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sd->exp_too_high_cnt = 0;
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} else if (sd->exp_too_low_cnt > 3) {
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exposure++;
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sd->exp_too_low_cnt = 0;
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}
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if (gain != orig_gain) {
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gain_ctrl->set(gspca_dev, gain);
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retval = 1;
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}
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if (exposure != orig_exposure) {
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exposure_ctrl->set(gspca_dev, exposure);
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retval = 1;
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}
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return retval;
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}
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