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ipa: raspberrypi: AGC: handle modes with different sensitivities

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When the sensor is switched to a mode with a different sensitivity,
the target exposure values need to be adjusted proportionately to
maintain the same image brightness.

Signed-off-by: David Plowman <david.plowman@raspberrypi.com>
Reviewed-by: Naushir Patuck <naush@raspberrypi.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
This commit is contained in:
David Plowman 2021-07-18 19:51:25 +01:00 • committed by Kieran Bingham
parent d0c429c34c
commit abaa45d627
2 changed files with 23 additions and 5 deletions
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27
src/ipa/raspberrypi/controller/rpi/agc.cpp
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@ -163,7 +163,7 @@ Agc::Agc(Controller *controller)
: AgcAlgorithm(controller), metering_mode_(nullptr),
exposure_mode_(nullptr), constraint_mode_(nullptr),
frame_count_(0), lock_count_(0),
last_target_exposure_(0s),
last_target_exposure_(0s), last_sensitivity_(0.0),
ev_(1.0), flicker_period_(0s),
max_shutter_(0s), fixed_shutter_(0s), fixed_analogue_gain_(0.0)
{
@ -268,9 +268,12 @@ void Agc::SetConstraintMode(std::string const &constraint_mode_name)
constraint_mode_name_ = constraint_mode_name;
}
void Agc::SwitchMode([[maybe_unused]] CameraMode const &camera_mode,
void Agc::SwitchMode(CameraMode const &camera_mode,
Metadata *metadata)
{
/* AGC expects the mode sensitivity always to be non-zero. */
ASSERT(camera_mode.sensitivity);
housekeepConfig();
Duration fixed_shutter = clipShutter(fixed_shutter_);
@ -292,9 +295,20 @@ void Agc::SwitchMode([[maybe_unused]] CameraMode const &camera_mode,
filtered_.shutter = fixed_shutter;
filtered_.analogue_gain = fixed_analogue_gain_;
} else if (status_.total_exposure_value) {
// On a mode switch, it's possible the exposure profile could change,
// or a fixed exposure/gain might be set so we divide up the exposure/
// gain again, but we don't change any target values.
// On a mode switch, various things could happen:
// - the exposure profile might change
// - a fixed exposure or gain might be set
// - the new mode's sensitivity might be different
// We cope with the last of these by scaling the target values. After
// that we just need to re-divide the exposure/gain according to the
// current exposure profile, which takes care of everything else.
double ratio = last_sensitivity_ / camera_mode.sensitivity;
target_.total_exposure_no_dg *= ratio;
target_.total_exposure *= ratio;
filtered_.total_exposure_no_dg *= ratio;
filtered_.total_exposure *= ratio;
divideUpExposure();
} else {
// We come through here on startup, when at least one of the shutter
@ -308,6 +322,9 @@ void Agc::SwitchMode([[maybe_unused]] CameraMode const &camera_mode,
}
writeAndFinish(metadata, false);
// We must remember the sensitivity of this mode for the next SwitchMode.
last_sensitivity_ = camera_mode.sensitivity;
}
void Agc::Prepare(Metadata *image_metadata)