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-rw-r--r--drivers/media/video/gspca/coarse_expo_autogain.h116
1 files changed, 116 insertions, 0 deletions
diff --git a/drivers/media/video/gspca/coarse_expo_autogain.h b/drivers/media/video/gspca/coarse_expo_autogain.h
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index 00000000000..1cb9d941eaf
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+++ b/drivers/media/video/gspca/coarse_expo_autogain.h
@@ -0,0 +1,116 @@
+/*
+ * Auto gain algorithm for camera's with a coarse exposure control
+ *
+ * Copyright (C) 2010 Hans de Goede <hdegoede@redhat.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+ */
+
+/* Autogain + exposure algorithm for cameras with a coarse exposure control
+ (usually this means we can only control the clockdiv to change exposure)
+ As changing the clockdiv so that the fps drops from 30 to 15 fps for
+ example, will lead to a huge exposure change (it effectively doubles),
+ this algorithm normally tries to only adjust the gain (between 40 and
+ 80 %) and if that does not help, only then changes exposure. This leads
+ to a much more stable image then using the knee algorithm which at
+ certain points of the knee graph will only try to adjust exposure,
+ which leads to oscilating as one exposure step is huge.
+
+ Note this assumes that the sd struct for the cam in question has
+ exp_too_high_cnt and exp_too_high_cnt int members for use by this function.
+
+ Returns 0 if no changes were made, 1 if the gain and or exposure settings
+ where changed. */
+static int gspca_coarse_grained_expo_autogain(struct gspca_dev *gspca_dev,
+ int avg_lum, int desired_avg_lum, int deadzone)
+{
+ int i, steps, gain, orig_gain, exposure, orig_exposure;
+ int gain_low, gain_high;
+ const struct ctrl *gain_ctrl = NULL;
+ const struct ctrl *exposure_ctrl = NULL;
+ struct sd *sd = (struct sd *) gspca_dev;
+ int retval = 0;
+
+ for (i = 0; i < gspca_dev->sd_desc->nctrls; i++) {
+ if (gspca_dev->ctrl_dis & (1 << i))
+ continue;
+ if (gspca_dev->sd_desc->ctrls[i].qctrl.id == V4L2_CID_GAIN)
+ gain_ctrl = &gspca_dev->sd_desc->ctrls[i];
+ if (gspca_dev->sd_desc->ctrls[i].qctrl.id == V4L2_CID_EXPOSURE)
+ exposure_ctrl = &gspca_dev->sd_desc->ctrls[i];
+ }
+ if (!gain_ctrl || !exposure_ctrl) {
+ PDEBUG(D_ERR, "Error: gspca_coarse_grained_expo_autogain "
+ "called on cam without gain or exposure");
+ return 0;
+ }
+
+ if (gain_ctrl->get(gspca_dev, &gain) ||
+ exposure_ctrl->get(gspca_dev, &exposure))
+ return 0;
+
+ orig_gain = gain;
+ orig_exposure = exposure;
+ gain_low =
+ (gain_ctrl->qctrl.maximum - gain_ctrl->qctrl.minimum) / 5 * 2;
+ gain_low += gain_ctrl->qctrl.minimum;
+ gain_high =
+ (gain_ctrl->qctrl.maximum - gain_ctrl->qctrl.minimum) / 5 * 4;
+ gain_high += gain_ctrl->qctrl.minimum;
+
+ /* If we are of a multiple of deadzone, do multiple steps to reach the
+ desired lumination fast (with the risc of a slight overshoot) */
+ steps = (desired_avg_lum - avg_lum) / deadzone;
+
+ PDEBUG(D_FRAM, "autogain: lum: %d, desired: %d, steps: %d",
+ avg_lum, desired_avg_lum, steps);
+
+ if ((gain + steps) > gain_high &&
+ sd->exposure < exposure_ctrl->qctrl.maximum) {
+ gain = gain_high;
+ sd->exp_too_low_cnt++;
+ } else if ((gain + steps) < gain_low &&
+ sd->exposure > exposure_ctrl->qctrl.minimum) {
+ gain = gain_low;
+ sd->exp_too_high_cnt++;
+ } else {
+ gain += steps;
+ if (gain > gain_ctrl->qctrl.maximum)
+ gain = gain_ctrl->qctrl.maximum;
+ else if (gain < gain_ctrl->qctrl.minimum)
+ gain = gain_ctrl->qctrl.minimum;
+ sd->exp_too_high_cnt = 0;
+ sd->exp_too_low_cnt = 0;
+ }
+
+ if (sd->exp_too_high_cnt > 3) {
+ exposure--;
+ sd->exp_too_high_cnt = 0;
+ } else if (sd->exp_too_low_cnt > 3) {
+ exposure++;
+ sd->exp_too_low_cnt = 0;
+ }
+
+ if (gain != orig_gain) {
+ gain_ctrl->set(gspca_dev, gain);
+ retval = 1;
+ }
+ if (exposure != orig_exposure) {
+ exposure_ctrl->set(gspca_dev, exposure);
+ retval = 1;
+ }
+
+ return retval;
+}