diff options
Diffstat (limited to 'drivers/media/video/gspca/coarse_expo_autogain.h')
| -rw-r--r-- | drivers/media/video/gspca/coarse_expo_autogain.h | 116 |
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 new file mode 100644 index 00000000000..1cb9d941eaf --- /dev/null +++ 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; +} |