Hans de Goede | 26984b0 | 2010-02-01 13:18:37 -0300 | [diff] [blame] | 1 | /* |
| 2 | * Auto gain algorithm for camera's with a coarse exposure control |
| 3 | * |
| 4 | * Copyright (C) 2010 Hans de Goede <hdegoede@redhat.com> |
| 5 | * |
| 6 | * This program is free software; you can redistribute it and/or modify |
| 7 | * it under the terms of the GNU General Public License as published by |
| 8 | * the Free Software Foundation; either version 2 of the License, or |
| 9 | * (at your option) any later version. |
| 10 | * |
| 11 | * This program is distributed in the hope that it will be useful, |
| 12 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 13 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 14 | * GNU General Public License for more details. |
| 15 | * |
| 16 | * You should have received a copy of the GNU General Public License |
| 17 | * along with this program; if not, write to the Free Software |
| 18 | * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA |
| 19 | */ |
| 20 | |
| 21 | /* Autogain + exposure algorithm for cameras with a coarse exposure control |
| 22 | (usually this means we can only control the clockdiv to change exposure) |
| 23 | As changing the clockdiv so that the fps drops from 30 to 15 fps for |
| 24 | example, will lead to a huge exposure change (it effectively doubles), |
| 25 | this algorithm normally tries to only adjust the gain (between 40 and |
| 26 | 80 %) and if that does not help, only then changes exposure. This leads |
| 27 | to a much more stable image then using the knee algorithm which at |
| 28 | certain points of the knee graph will only try to adjust exposure, |
| 29 | which leads to oscilating as one exposure step is huge. |
| 30 | |
| 31 | Note this assumes that the sd struct for the cam in question has |
| 32 | exp_too_high_cnt and exp_too_high_cnt int members for use by this function. |
| 33 | |
| 34 | Returns 0 if no changes were made, 1 if the gain and or exposure settings |
| 35 | where changed. */ |
| 36 | static int gspca_coarse_grained_expo_autogain(struct gspca_dev *gspca_dev, |
| 37 | int avg_lum, int desired_avg_lum, int deadzone) |
| 38 | { |
| 39 | int i, steps, gain, orig_gain, exposure, orig_exposure; |
| 40 | int gain_low, gain_high; |
| 41 | const struct ctrl *gain_ctrl = NULL; |
| 42 | const struct ctrl *exposure_ctrl = NULL; |
| 43 | struct sd *sd = (struct sd *) gspca_dev; |
| 44 | int retval = 0; |
| 45 | |
| 46 | for (i = 0; i < gspca_dev->sd_desc->nctrls; i++) { |
| 47 | if (gspca_dev->ctrl_dis & (1 << i)) |
| 48 | continue; |
| 49 | if (gspca_dev->sd_desc->ctrls[i].qctrl.id == V4L2_CID_GAIN) |
| 50 | gain_ctrl = &gspca_dev->sd_desc->ctrls[i]; |
| 51 | if (gspca_dev->sd_desc->ctrls[i].qctrl.id == V4L2_CID_EXPOSURE) |
| 52 | exposure_ctrl = &gspca_dev->sd_desc->ctrls[i]; |
| 53 | } |
| 54 | if (!gain_ctrl || !exposure_ctrl) { |
| 55 | PDEBUG(D_ERR, "Error: gspca_coarse_grained_expo_autogain " |
| 56 | "called on cam without gain or exposure"); |
| 57 | return 0; |
| 58 | } |
| 59 | |
| 60 | if (gain_ctrl->get(gspca_dev, &gain) || |
| 61 | exposure_ctrl->get(gspca_dev, &exposure)) |
| 62 | return 0; |
| 63 | |
| 64 | orig_gain = gain; |
| 65 | orig_exposure = exposure; |
| 66 | gain_low = |
| 67 | (gain_ctrl->qctrl.maximum - gain_ctrl->qctrl.minimum) / 5 * 2; |
| 68 | gain_low += gain_ctrl->qctrl.minimum; |
| 69 | gain_high = |
| 70 | (gain_ctrl->qctrl.maximum - gain_ctrl->qctrl.minimum) / 5 * 4; |
| 71 | gain_high += gain_ctrl->qctrl.minimum; |
| 72 | |
| 73 | /* If we are of a multiple of deadzone, do multiple steps to reach the |
| 74 | desired lumination fast (with the risc of a slight overshoot) */ |
| 75 | steps = (desired_avg_lum - avg_lum) / deadzone; |
| 76 | |
| 77 | PDEBUG(D_FRAM, "autogain: lum: %d, desired: %d, steps: %d", |
| 78 | avg_lum, desired_avg_lum, steps); |
| 79 | |
| 80 | if ((gain + steps) > gain_high && |
| 81 | sd->exposure < exposure_ctrl->qctrl.maximum) { |
| 82 | gain = gain_high; |
| 83 | sd->exp_too_low_cnt++; |
| 84 | } else if ((gain + steps) < gain_low && |
| 85 | sd->exposure > exposure_ctrl->qctrl.minimum) { |
| 86 | gain = gain_low; |
| 87 | sd->exp_too_high_cnt++; |
| 88 | } else { |
| 89 | gain += steps; |
| 90 | if (gain > gain_ctrl->qctrl.maximum) |
| 91 | gain = gain_ctrl->qctrl.maximum; |
| 92 | else if (gain < gain_ctrl->qctrl.minimum) |
| 93 | gain = gain_ctrl->qctrl.minimum; |
| 94 | sd->exp_too_high_cnt = 0; |
| 95 | sd->exp_too_low_cnt = 0; |
| 96 | } |
| 97 | |
| 98 | if (sd->exp_too_high_cnt > 3) { |
| 99 | exposure--; |
| 100 | sd->exp_too_high_cnt = 0; |
| 101 | } else if (sd->exp_too_low_cnt > 3) { |
| 102 | exposure++; |
| 103 | sd->exp_too_low_cnt = 0; |
| 104 | } |
| 105 | |
| 106 | if (gain != orig_gain) { |
| 107 | gain_ctrl->set(gspca_dev, gain); |
| 108 | retval = 1; |
| 109 | } |
| 110 | if (exposure != orig_exposure) { |
| 111 | exposure_ctrl->set(gspca_dev, exposure); |
| 112 | retval = 1; |
| 113 | } |
| 114 | |
| 115 | return retval; |
| 116 | } |