[libcamera-devel] [PATCH 2/2] ipa: raspberrypi: AGC: handle modes with different sensitivities
Naushir Patuck
naush at raspberrypi.com
Wed Jun 2 12:03:32 CEST 2021
Hi David,
Thank you for your work.
On Thu, 27 May 2021 at 09:45, David Plowman <david.plowman at raspberrypi.com>
wrote:
> 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 at raspberrypi.com>
>
These changes look sensible to me.
Reviewed-by: Naushir Patuck <naush at raspberrpi.com>
> ---
> src/ipa/raspberrypi/controller/rpi/agc.cpp | 25 +++++++++++++++++-----
> src/ipa/raspberrypi/controller/rpi/agc.hpp | 1 +
> 2 files changed, 21 insertions(+), 5 deletions(-)
>
> diff --git a/src/ipa/raspberrypi/controller/rpi/agc.cpp
> b/src/ipa/raspberrypi/controller/rpi/agc.cpp
> index f4cd5d26..6f0e9702 100644
> --- a/src/ipa/raspberrypi/controller/rpi/agc.cpp
> +++ b/src/ipa/raspberrypi/controller/rpi/agc.cpp
> @@ -155,7 +155,7 @@ Agc::Agc(Controller *controller)
> : AgcAlgorithm(controller), metering_mode_(nullptr),
> exposure_mode_(nullptr), constraint_mode_(nullptr),
> frame_count_(0), lock_count_(0),
> - last_target_exposure_(0.0),
> + last_target_exposure_(0.0), last_sensitivity_(0.0),
> ev_(1.0), flicker_period_(0.0),
> max_shutter_(0), fixed_shutter_(0), fixed_analogue_gain_(0.0)
> {
> @@ -261,7 +261,7 @@ 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)
> {
> housekeepConfig();
> @@ -285,9 +285,20 @@ 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
> @@ -301,6 +312,10 @@ void Agc::SwitchMode([[maybe_unused]] CameraMode
> const &camera_mode,
> }
>
> writeAndFinish(metadata, false);
> +
> + // We must remember the sensitivity of this mode for the next
> SwitchMode.
> + ASSERT(camera_mode.sensitivity != 0.0);
> + last_sensitivity_ = camera_mode.sensitivity;
> }
>
> void Agc::Prepare(Metadata *image_metadata)
> diff --git a/src/ipa/raspberrypi/controller/rpi/agc.hpp
> b/src/ipa/raspberrypi/controller/rpi/agc.hpp
> index 0427fb59..025878a2 100644
> --- a/src/ipa/raspberrypi/controller/rpi/agc.hpp
> +++ b/src/ipa/raspberrypi/controller/rpi/agc.hpp
> @@ -122,6 +122,7 @@ private:
> int lock_count_;
> DeviceStatus last_device_status_;
> double last_target_exposure_;
> + double last_sensitivity_; // sensitivity of the previous camera
> mode
> // Below here the "settings" that applications can change.
> std::string metering_mode_name_;
> std::string exposure_mode_name_;
> --
> 2.20.1
>
>
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