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/*
# (C) 2008-2009 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 Lesser General Public License as published by
# the Free Software Foundation; either version 2.1 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 Lesser General Public License for more details.
#
# You should have received a copy of the GNU Lesser 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
*/
#include <errno.h>
#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#include <syscall.h>
#include <unistd.h>
#include "libv4lprocessing.h"
#include "libv4lprocessing-priv.h"
#include "../libv4lconvert-priv.h" /* for PIX_FMT defines */
static int autogain_active(struct v4lprocessing_data *data) {
return v4lcontrol_get_ctrl(data->control, V4LCONTROL_AUTOGAIN);
}
/* auto gain and exposure algorithm based on the knee algorithm described here:
http://ytse.tricolour.net/docs/LowLightOptimization.html */
static int autogain_calculate_lookup_tables(
struct v4lprocessing_data *data,
unsigned char *buf, const struct v4l2_format *fmt)
{
int x, y, target, steps, avg_lum = 0;
int gain, exposure, orig_gain, orig_exposure;
struct v4l2_control ctrl;
struct v4l2_queryctrl gainctrl, expoctrl;
const int deadzone = 8;
ctrl.id = V4L2_CID_EXPOSURE;
expoctrl.id = V4L2_CID_EXPOSURE;
if (syscall(SYS_ioctl, data->fd, VIDIOC_QUERYCTRL, &expoctrl) ||
syscall(SYS_ioctl, data->fd, VIDIOC_G_CTRL, &ctrl))
return 0;
exposure = orig_exposure = ctrl.value;
ctrl.id = V4L2_CID_GAIN;
gainctrl.id = V4L2_CID_GAIN;
if (syscall(SYS_ioctl, data->fd, VIDIOC_QUERYCTRL, &gainctrl) ||
syscall(SYS_ioctl, data->fd, VIDIOC_G_CTRL, &ctrl))
return 0;
gain = orig_gain = ctrl.value;
switch (fmt->fmt.pix.pixelformat) {
case V4L2_PIX_FMT_SGBRG8:
case V4L2_PIX_FMT_SGRBG8:
case V4L2_PIX_FMT_SBGGR8:
case V4L2_PIX_FMT_SRGGB8:
buf += fmt->fmt.pix.height * fmt->fmt.pix.bytesperline / 4 +
fmt->fmt.pix.width / 4;
for (y = 0; y < fmt->fmt.pix.height / 2; y++) {
for (x = 0; x < fmt->fmt.pix.width / 2; x++) {
avg_lum += *buf++;
}
buf += fmt->fmt.pix.bytesperline - fmt->fmt.pix.width / 2;
}
avg_lum /= fmt->fmt.pix.height * fmt->fmt.pix.width / 4;
break;
case V4L2_PIX_FMT_RGB24:
case V4L2_PIX_FMT_BGR24:
buf += fmt->fmt.pix.height * fmt->fmt.pix.bytesperline / 4 +
fmt->fmt.pix.width * 3 / 4;
for (y = 0; y < fmt->fmt.pix.height / 2; y++) {
for (x = 0; x < fmt->fmt.pix.width / 2; x++) {
avg_lum += *buf++;
avg_lum += *buf++;
avg_lum += *buf++;
}
buf += fmt->fmt.pix.bytesperline - fmt->fmt.pix.width * 3 / 2;
}
avg_lum /= fmt->fmt.pix.height * fmt->fmt.pix.width * 3 / 4;
break;
}
/* If we are off a multiple of deadzone, do multiple steps to reach the
desired lumination fast (with the risc of a slight overshoot) */
target = v4lcontrol_get_ctrl(data->control, V4LCONTROL_AUTOGAIN_TARGET);
steps = abs(target - avg_lum) / deadzone;
for (x = 0; x < steps; x++) {
if (avg_lum > target) {
if (exposure > expoctrl.default_value)
exposure--;
else if (gain > gainctrl.default_value)
gain--;
else if (exposure > expoctrl.minimum)
exposure--;
else if (gain > gainctrl.minimum)
gain--;
else
break;
} else {
if (gain < gainctrl.default_value)
gain++;
else if (exposure < expoctrl.default_value)
exposure++;
else if (gain < gainctrl.maximum)
gain++;
else if (exposure < expoctrl.maximum)
exposure++;
else
break;
}
}
if (gain != orig_gain) {
ctrl.id = V4L2_CID_GAIN;
ctrl.value = gain;
syscall(SYS_ioctl, data->fd, VIDIOC_S_CTRL, &ctrl);
}
if (exposure != orig_exposure) {
ctrl.id = V4L2_CID_EXPOSURE;
ctrl.value = exposure;
syscall(SYS_ioctl, data->fd, VIDIOC_S_CTRL, &ctrl);
}
return 0;
}
struct v4lprocessing_filter autogain_filter = {
autogain_active, autogain_calculate_lookup_tables };
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