[media] gspca: New file autogain_functions.h

This file contains functions for the auto gain.
It must be used with the new control mechanism.

Acked-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Jean-François Moine <moinejf@free.fr>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

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 00000000000..46777eee678
--- /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;
+}