[libcamera-devel] [PATCH v2 2/2] libcamera: raspberrypi: recalculate camera exposure/gain when camera mode changes

[Laurent Pinchart]

Hi David,

Thank you for the patch.

Nitpicking a little bit, the commit message subject prefix should be
"libcamera: ipa: raspberrypi:". Same for 1/2.

On Thu, Jun 18, 2020 at 12:12:36PM +0100, David Plowman wrote:
> This commit causes the AGC to recalculate its camera exposure/gain
> values when the camera mode changes. For example it's possible
> that the exposure profile could be changed by the application so
> the division between exposure time and analogue gain may be
> different.
> 
> The other underlying reason (and which this commit accomplishes too)
> is that the sensor's line timing may change in a new mode, and because
> V4L2 drivers store a number of exposure _lines_, the resulting _time_
> will "change under our feet". So we have to go through the process of
> recalculating the correct number of lines and writing this back to the
> sensor with every mode switch, regardless of anything else.

I wonder if in the future we shouldn't try to abstract this in the
CameraSensor class, to avoid having to deal with this sensor-specific
behaviour in IPAs. Not something for this patch series.

> Signed-off-by: David Plowman <david.plowman at raspberrypi.com>

Reviewed-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>

Both patches applied to my tree with the subjects updated. I'll push to
master after running the compilation tests.

> ---
>  src/ipa/raspberrypi/controller/rpi/agc.cpp | 12 +++++++++++
>  src/ipa/raspberrypi/controller/rpi/agc.hpp |  1 +
>  src/ipa/raspberrypi/raspberrypi.cpp        | 25 +++++++++++-----------
>  3 files changed, 26 insertions(+), 12 deletions(-)
> 
> diff --git a/src/ipa/raspberrypi/controller/rpi/agc.cpp b/src/ipa/raspberrypi/controller/rpi/agc.cpp
> index a474287..c02b5ec 100644
> --- a/src/ipa/raspberrypi/controller/rpi/agc.cpp
> +++ b/src/ipa/raspberrypi/controller/rpi/agc.cpp
> @@ -221,6 +221,18 @@ void Agc::SetConstraintMode(std::string const &constraint_mode_name)
>  	constraint_mode_name_ = constraint_mode_name;
>  }
>  
> +void Agc::SwitchMode(CameraMode const &camera_mode, Metadata *metadata)
> +{
> +	// On a mode switch, it's possible the exposure profile could change,
> +	// so we run through the dividing up of exposure/gain again and
> +	// write the results into the metadata we've been given.
> +	if (status_.total_exposure_value) {
> +		housekeepConfig();
> +		divvyupExposure();
> +		writeAndFinish(metadata, false);
> +	}
> +}
> +
>  void Agc::Prepare(Metadata *image_metadata)
>  {
>  	AgcStatus status;
> diff --git a/src/ipa/raspberrypi/controller/rpi/agc.hpp b/src/ipa/raspberrypi/controller/rpi/agc.hpp
> index dbcefba..9a7e89c 100644
> --- a/src/ipa/raspberrypi/controller/rpi/agc.hpp
> +++ b/src/ipa/raspberrypi/controller/rpi/agc.hpp
> @@ -75,6 +75,7 @@ public:
>  	void SetMeteringMode(std::string const &metering_mode_name) override;
>  	void SetExposureMode(std::string const &exposure_mode_name) override;
>  	void SetConstraintMode(std::string const &contraint_mode_name) override;
> +	void SwitchMode(CameraMode const &camera_mode, Metadata *metadata) override;
>  	void Prepare(Metadata *image_metadata) override;
>  	void Process(StatisticsPtr &stats, Metadata *image_metadata) override;
>  
> diff --git a/src/ipa/raspberrypi/raspberrypi.cpp b/src/ipa/raspberrypi/raspberrypi.cpp
> index d6fd3df..42c84b1 100644
> --- a/src/ipa/raspberrypi/raspberrypi.cpp
> +++ b/src/ipa/raspberrypi/raspberrypi.cpp
> @@ -247,29 +247,30 @@ void IPARPi::configure(const CameraSensorInfo &sensorInfo,
>  		mistrust_count_ = helper_->MistrustFramesStartup();
>  	}
>  
> +	struct AgcStatus agcStatus;
> +	/* These zero values mean not program anything (unless overwritten). */
> +	agcStatus.shutter_time = 0.0;
> +	agcStatus.analogue_gain = 0.0;
> +
>  	if (!controllerInit_) {
>  		/* Load the tuning file for this sensor. */
>  		controller_.Read(tuningFile_.c_str());
>  		controller_.Initialise();
>  		controllerInit_ = true;
>  
> -		/* Calculate initial values for gain and exposure. */
> -		int32_t gain_code = helper_->GainCode(DEFAULT_ANALOGUE_GAIN);
> -		int32_t exposure_lines = helper_->ExposureLines(DEFAULT_EXPOSURE_TIME);
> -
> -		ControlList ctrls(unicam_ctrls_);
> -		ctrls.set(V4L2_CID_ANALOGUE_GAIN, gain_code);
> -		ctrls.set(V4L2_CID_EXPOSURE, exposure_lines);
> -
> -		IPAOperationData op;
> -		op.operation = RPI_IPA_ACTION_V4L2_SET_STAGGERED;
> -		op.controls.push_back(ctrls);
> -		queueFrameAction.emit(0, op);
> +		/* Supply initial values for gain and exposure. */
> +		agcStatus.shutter_time = DEFAULT_EXPOSURE_TIME;
> +		agcStatus.analogue_gain = DEFAULT_ANALOGUE_GAIN;
>  	}
>  
>  	RPi::Metadata metadata;
>  	controller_.SwitchMode(mode_, &metadata);
>  
> +	/* SwitchMode may supply updated exposure/gain values to use. */
> +	metadata.Get("agc.status", agcStatus);
> +	if (agcStatus.shutter_time != 0.0 && agcStatus.analogue_gain != 0.0)
> +		applyAGC(&agcStatus);
> +
>  	lastMode_ = mode_;
>  }
>  

-- 
Regards,

Laurent Pinchart