[libcamera-devel] [RFC 1/4] libcamera: camera_sensor: Cache rotationTransform_

[Jacopo Mondi]

Hi Umang

On Wed, Jun 21, 2023 at 10:51:33AM +0530, Umang Jain wrote:
> Hi Jacopo,
>
> Thank you for the patch.
>
> On 6/20/23 7:59 PM, Jacopo Mondi via libcamera-devel wrote:
> > The rotationTransform_ depends on a V4L2 control whose value does not
> > change for the whole lifetime of the camera.
> >
> > Instead of re-calculating it everytime the camera is configured, cache
> > it at properties initialization time.
> >
> > Signed-off-by: Jacopo Mondi <jacopo.mondi at ideasonboard.com>
> > ---
> >   include/libcamera/internal/camera_sensor.h |  1 +
> >   src/libcamera/camera_sensor.cpp            | 54 +++++++++++++---------
> >   2 files changed, 32 insertions(+), 23 deletions(-)
> >
> > diff --git a/include/libcamera/internal/camera_sensor.h b/include/libcamera/internal/camera_sensor.h
> > index 02c77ab037da..02b4b4d25e6d 100644
> > --- a/include/libcamera/internal/camera_sensor.h
> > +++ b/include/libcamera/internal/camera_sensor.h
> > @@ -107,6 +107,7 @@ private:
> >   	Rectangle activeArea_;
> >   	const BayerFormat *bayerFormat_;
> >   	bool supportFlips_;
> > +	Transform rotationTransform_;
> >   	ControlList properties_;
> > diff --git a/src/libcamera/camera_sensor.cpp b/src/libcamera/camera_sensor.cpp
> > index f3a5aa37149f..a15a6c89c5c8 100644
> > --- a/src/libcamera/camera_sensor.cpp
> > +++ b/src/libcamera/camera_sensor.cpp
> > @@ -461,18 +461,36 @@ int CameraSensor::initProperties()
> >   	const auto &rotationControl = controls.find(V4L2_CID_CAMERA_SENSOR_ROTATION);
> >   	if (rotationControl != controls.end()) {
> > +		propertyValue = rotationControl->second.def().get<int32_t>();
> > +
> >   		/*
> > -		 * validateTransform() compensates for the mounting rotation.
> > -		 * However, as a camera sensor can only compensate rotations
> > -		 * by applying H/VFlips, only rotation of 180 degrees are
> > -		 * automatically compensated. The other valid rotations (Rot90
> > -		 * and Rot270) require transposition, which the camera sensor
> > -		 * cannot perform, so leave them untouched.
> > +		 * Cache the Transform associated with the camera mounting
> > +		 * rotation for later use in validateTransform().
> > +		 */
> > +		bool success;
> > +		rotationTransform_ = transformFromRotation(propertyValue, &success);
>
> Probably a good time to convert to std::optional<> here? Or it can be done
> on top. Either way I don't mind, as long as it happens ;-)

Would would it give an std::optional<> here ?

In case "nothing" has to be done, transformFromRotation() returns
Identity and pipeline handlers can safely pass it to
CameraSensor::setFormat(). True we can make the optional "transform"
argument of CameraSensor::setFormat() and std::optional<> too...

>
> Other than that, the code looks fine to me.
>
> Reviewed-by: Umang Jain <umang.jain at ideasonboard.com>
>
> > +		if (!success) {
> > +			LOG(CameraSensor, Warning)
> > +				<< "Invalid rotation of " << propertyValue
> > +				<< " degrees - ignoring";
> > +			rotationTransform_ = Transform::Identity;
> > +		}
> > +
> > +		/*
> > +		 * Adjust property::Rotation as validateTransform() compensates
> > +		 * for the mounting rotation. However, as a camera sensor can
> > +		 * only compensate rotations by applying H/VFlips, only rotation
> > +		 * of 180 degrees are automatically compensated. The other valid
> > +		 * rotations (Rot90 and Rot270) require transposition, which the
> > +		 * camera sensor cannot perform, so leave them untouched.
> >   		 */
> > -		propertyValue = rotationControl->second.def().get<int32_t>();
> >   		if (propertyValue == 180 && supportFlips_)
> >   			propertyValue = 0;
> >   		properties_.set(properties::Rotation, propertyValue);
> > +	} else {
> > +		LOG(CameraSensor, Warning)
> > +			<< "Rotation control not available, default to 0 degreees";
> > +		rotationTransform_ = Transform::Identity;
> >   	}
> >   	properties_.set(properties::PixelArraySize, pixelArraySize_);
> > @@ -1038,21 +1056,11 @@ void CameraSensor::updateControlInfo()
> >    */
> >   Transform CameraSensor::validateTransform(Transform *transform) const
> >   {
> > -	/* Adjust the requested transform to compensate the sensor mounting rotation. */
> > -	const ControlInfoMap &controls = subdev_->controls();
> > -	int rotation = 0;
> > -
> > -	const auto &rotationControl = controls.find(V4L2_CID_CAMERA_SENSOR_ROTATION);
> > -	if (rotationControl != controls.end())
> > -		rotation = rotationControl->second.def().get<int32_t>();
> > -
> > -	bool success;
> > -	Transform rotationTransform = transformFromRotation(rotation, &success);
> > -	if (!success)
> > -		LOG(CameraSensor, Warning) << "Invalid rotation of " << rotation
> > -					   << " degrees - ignoring";
> > -
> > -	Transform combined = *transform * rotationTransform;
> > +	/*
> > +	 * Combine the requested transform to compensate the sensor mounting
> > +	 * rotation.
> > +	 */
> > +	Transform combined = *transform * rotationTransform_;
> >   	/*
> >   	 * We combine the platform and user transform, but must "adjust away"
> > @@ -1083,7 +1091,7 @@ Transform CameraSensor::validateTransform(Transform *transform) const
> >   		 * rise to this is the inverse of the rotation. (Recall that
> >   		 * combined = transform * rotationTransform.)
> >   		 */
> > -		*transform = -rotationTransform;
> > +		*transform = -rotationTransform_;
> >   		combined = Transform::Identity;
> >   	}
>