diff options
Diffstat (limited to 'drivers/media')
| -rw-r--r-- | drivers/media/video/gspca/autogain_functions.h | 179 |
1 files changed, 179 insertions, 0 deletions
diff --git a/drivers/media/video/gspca/autogain_functions.h b/drivers/media/video/gspca/autogain_functions.h new file mode 100644 index 000000000000..46777eee678b --- /dev/null +++ b/drivers/media/video/gspca/autogain_functions.h @@ -0,0 +1,179 @@ +/* + * Functions for auto gain. + * + * Copyright (C) 2010-2011 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 + */ + +/* auto gain and exposure algorithm based on the knee algorithm described here: + http://ytse.tricolour.net/docs/LowLightOptimization.html + + Returns 0 if no changes were made, 1 if the gain and or exposure settings + where changed. */ +static inline int auto_gain_n_exposure( + struct gspca_dev *gspca_dev, + int avg_lum, + int desired_avg_lum, + int deadzone, + int gain_knee, + int exposure_knee) +{ + struct sd *sd = (struct sd *) gspca_dev; + int i, steps, gain, orig_gain, exposure, orig_exposure; + int retval = 0; + + orig_gain = gain = sd->ctrls[GAIN].val; + orig_exposure = exposure = sd->ctrls[EXPOSURE].val; + + /* 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 = abs(desired_avg_lum - avg_lum) / deadzone; + + PDEBUG(D_FRAM, "autogain: lum: %d, desired: %d, steps: %d", + avg_lum, desired_avg_lum, steps); + + for (i = 0; i < steps; i++) { + if (avg_lum > desired_avg_lum) { + if (gain > gain_knee) + gain--; + else if (exposure > exposure_knee) + exposure--; + else if (gain > sd->ctrls[GAIN].def) + gain--; + else if (exposure > sd->ctrls[EXPOSURE].min) + exposure--; + else if (gain > sd->ctrls[GAIN].min) + gain--; + else + break; + } else { + if (gain < sd->ctrls[GAIN].def) + gain++; + else if (exposure < exposure_knee) + exposure++; + else if (gain < gain_knee) + gain++; + else if (exposure < sd->ctrls[EXPOSURE].max) + exposure++; + else if (gain < sd->ctrls[GAIN].max) + gain++; + else + break; + } + } + + if (gain != orig_gain) { + sd->ctrls[GAIN].val = gain; + setgain(gspca_dev); + retval = 1; + } + if (exposure != orig_exposure) { + sd->ctrls[EXPOSURE].val = exposure; + setexposure(gspca_dev); + retval = 1; + } + + if (retval) + PDEBUG(D_FRAM, "autogain: changed gain: %d, expo: %d", + gain, exposure); + return retval; +} + +/* 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 inline int coarse_grained_expo_autogain( + struct gspca_dev *gspca_dev, + int avg_lum, + int desired_avg_lum, + int deadzone) +{ + struct sd *sd = (struct sd *) gspca_dev; + int steps, gain, orig_gain, exposure, orig_exposure; + int gain_low, gain_high; + int retval = 0; + + orig_gain = gain = sd->ctrls[GAIN].val; + orig_exposure = exposure = sd->ctrls[EXPOSURE].val; + + gain_low = (sd->ctrls[GAIN].max - sd->ctrls[GAIN].min) / 5 * 2; + gain_low += sd->ctrls[GAIN].min; + gain_high = (sd->ctrls[GAIN].max - sd->ctrls[GAIN].min) / 5 * 4; + gain_high += sd->ctrls[GAIN].min; + + /* 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 && + exposure < sd->ctrls[EXPOSURE].max) { + gain = gain_high; + sd->exp_too_low_cnt++; + sd->exp_too_high_cnt = 0; + } else if ((gain + steps) < gain_low && + exposure > sd->ctrls[EXPOSURE].min) { + gain = gain_low; + sd->exp_too_high_cnt++; + sd->exp_too_low_cnt = 0; + } else { + gain += steps; + if (gain > sd->ctrls[GAIN].max) + gain = sd->ctrls[GAIN].max; + else if (gain < sd->ctrls[GAIN].min) + gain = sd->ctrls[GAIN].min; + 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) { + sd->ctrls[GAIN].val = gain; + setgain(gspca_dev); + retval = 1; + } + if (exposure != orig_exposure) { + sd->ctrls[EXPOSURE].val = exposure; + setexposure(gspca_dev); + retval = 1; + } + + if (retval) + PDEBUG(D_FRAM, "autogain: changed gain: %d, expo: %d", + gain, exposure); + return retval; +} |