libcamera: ipu3: imgu: Calculate ImgU pipe configuration

Instrument the ImgU component to dynamically calculate the image
manipulation pipeline intermediate sizes.

To correctly configure the ImgU it is necessary to program the IF, BDS
and GDC sizes, which are currently fixed to the input frame size.

The procedure used to calculate the intermediate sizes has been ported
from the pipe_config.py python script, available at:
https://github.com/intel/intel-ipu3-pipecfg
at revision:
61e83f2f7606 ("Add more information into README")

Define two structures (ImgUDevice::Pipe and ImgUDevice::PipeConfig)
to allow the pipeline handler to supply and retrieve configuration
parameters from the ImgU.

Finally, add a new operation to the ImgUDevice that calculates
the pipe configuration parameters based on the requested input and
output sizes.

Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Niklas Söderlund <niklas.soderlund@ragnatech.se>
Signed-off-by: Jacopo Mondi <jacopo@jmondi.org>

3 files changed, 376 insertions, 1 deletions

diff --git a/src/libcamera/pipeline/ipu3/imgu.cpp b/src/libcamera/pipeline/ipu3/imgu.cpp
index 4bec4b2f..e621e293 100644
--- a/src/libcamera/pipeline/ipu3/imgu.cpp
+++ b/src/libcamera/pipeline/ipu3/imgu.cpp
@@ -7,6 +7,9 @@
 
 #include "imgu.h"
 
+#include <limits>
+#include <math.h>
+
 #include <linux/media-bus-format.h>
 
 #include <libcamera/formats.h>
@@ -14,11 +17,306 @@
 
 #include "libcamera/internal/log.h"
 #include "libcamera/internal/media_device.h"
+#include "libcamera/internal/utils.h"
 
 namespace libcamera {
 
 LOG_DECLARE_CATEGORY(IPU3)
 
+namespace {
+
+/*
+ * The procedure to calculate the ImgU pipe configuration has been ported
+ * from the pipe_config.py python script, available at:
+ * https://github.com/intel/intel-ipu3-pipecfg
+ * at revision: 61e83f2f7606 ("Add more information into README")
+ */
+
+static constexpr unsigned int FILTER_H = 4;
+
+static constexpr unsigned int IF_ALIGN_W = 2;
+static constexpr unsigned int IF_ALIGN_H = 4;
+
+static constexpr unsigned int BDS_ALIGN_W = 2;
+static constexpr unsigned int BDS_ALIGN_H = 4;
+
+static constexpr unsigned int IF_CROP_MAX_W = 40;
+static constexpr unsigned int IF_CROP_MAX_H = 540;
+
+static constexpr float BDS_SF_MAX = 2.5;
+static constexpr float BDS_SF_MIN = 1.0;
+static constexpr float BDS_SF_STEP = 0.03125;
+
+/* BSD scaling factors: min=1, max=2.5, step=1/32 */
+const std::vector<float> bdsScalingFactors = {
+	1, 1.03125, 1.0625, 1.09375, 1.125, 1.15625, 1.1875, 1.21875, 1.25,
+	1.28125, 1.3125, 1.34375, 1.375, 1.40625, 1.4375, 1.46875, 1.5, 1.53125,
+	1.5625, 1.59375, 1.625, 1.65625, 1.6875, 1.71875, 1.75, 1.78125, 1.8125,
+	1.84375, 1.875, 1.90625, 1.9375, 1.96875, 2, 2.03125, 2.0625, 2.09375,
+	2.125, 2.15625, 2.1875, 2.21875, 2.25, 2.28125, 2.3125, 2.34375, 2.375,
+	2.40625, 2.4375, 2.46875, 2.5
+};
+
+/* GDC scaling factors: min=1, max=16, step=1/4 */
+const std::vector<float> gdcScalingFactors = {
+	1, 1.25, 1.5, 1.75, 2, 2.25, 2.5, 2.75, 3, 3.25, 3.5, 3.75, 4, 4.25,
+	4.5, 4.75, 5, 5.25, 5.5, 5.75, 6, 6.25, 6.5, 6.75, 7, 7.25, 7.5, 7.75,
+	8, 8.25, 8.5, 8.75, 9, 9.25, 9.5, 9.75, 10, 10.25, 10.5, 10.75, 11,
+	11.25, 11.5, 11.75, 12, 12.25, 12.5, 12.75, 13, 13.25, 13.5, 13.75, 14,
+	14.25, 14.5, 14.75, 15, 15.25, 15.5, 15.75, 16,
+};
+
+std::vector<ImgUDevice::PipeConfig> pipeConfigs;
+
+struct FOV {
+	float w;
+	float h;
+
+	bool isLarger(const FOV &other)
+	{
+		if (w > other.w)
+			return true;
+		if (w == other.w && h > other.h)
+			return true;
+		return false;
+	}
+};
+
+/* Approximate a scaling factor sf to the closest one available in a range. */
+float findScaleFactor(float sf, const std::vector<float> &range,
+		      bool roundDown = false)
+{
+	if (sf <= range[0])
+		return range[0];
+	if (sf >= range[range.size() - 1])
+		return range[range.size() - 1];
+
+	float bestDiff = std::numeric_limits<float>::max();
+	unsigned int index = 0;
+	for (unsigned int i = 0; i < range.size(); ++i) {
+		float diff = std::abs(sf - range[i]);
+		if (diff < bestDiff) {
+			bestDiff = diff;
+			index = i;
+		}
+	}
+
+	if (roundDown && index > 0 && sf < range[index])
+		index--;
+
+	return range[index];
+}
+
+bool isSameRatio(const Size &in, const Size &out)
+{
+	float inRatio = static_cast<float>(in.width) / in.height;
+	float outRatio = static_cast<float>(out.width) / out.height;
+
+	if (std::abs(inRatio - outRatio) > 0.1)
+		return false;
+
+	return true;
+}
+
+void calculateBDSHeight(ImgUDevice::Pipe *pipe, const Size &iif, const Size &gdc,
+			unsigned int bdsWidth, float bdsSF)
+{
+	unsigned int minIFHeight = iif.height - IF_CROP_MAX_H;
+	unsigned int minBDSHeight = gdc.height + FILTER_H * 2;
+	unsigned int ifHeight;
+	float bdsHeight;
+
+	if (!isSameRatio(pipe->input, gdc)) {
+		float estIFHeight = (iif.width * gdc.height) /
+				    static_cast<float>(gdc.width);
+		estIFHeight = utils::clamp<float>(estIFHeight, minIFHeight, iif.height);
+		bool found = false;
+
+		ifHeight = utils::alignUp(estIFHeight, IF_ALIGN_H);
+		while (ifHeight >= minIFHeight && ifHeight / bdsSF >= minBDSHeight) {
+
+			bdsHeight = ifHeight / bdsSF;
+			if (std::fmod(bdsHeight, 1.0) == 0) {
+				unsigned int bdsIntHeight = static_cast<unsigned int>(bdsHeight);
+
+				if (!(bdsIntHeight % BDS_ALIGN_H)) {
+					found = true;
+					break;
+				}
+			}
+
+			ifHeight -= IF_ALIGN_H;
+		}
+
+		ifHeight = utils::alignUp(estIFHeight, IF_ALIGN_H);
+		while (ifHeight <= iif.height && ifHeight / bdsSF >= minBDSHeight) {
+
+			bdsHeight = ifHeight / bdsSF;
+			if (std::fmod(bdsHeight, 1.0) == 0) {
+				unsigned int bdsIntHeight = static_cast<unsigned int>(bdsHeight);
+
+				if (!(bdsIntHeight % BDS_ALIGN_H)) {
+					found = true;
+					break;
+				}
+			}
+
+			ifHeight += IF_ALIGN_H;
+		}
+
+		if (found) {
+			unsigned int bdsIntHeight = static_cast<unsigned int>(bdsHeight);
+
+			pipeConfigs.push_back({ bdsSF, { iif.width, ifHeight },
+						{ bdsWidth, bdsIntHeight }, gdc });
+			return;
+		}
+	} else {
+		ifHeight = utils::alignUp(iif.height, IF_ALIGN_H);
+		while (ifHeight > minIFHeight && ifHeight / bdsSF >= minBDSHeight) {
+
+			bdsHeight = ifHeight / bdsSF;
+			if (std::fmod(ifHeight, 1.0) == 0 && std::fmod(bdsHeight, 1.0) == 0) {
+				unsigned int bdsIntHeight = static_cast<unsigned int>(bdsHeight);
+
+				if (!(ifHeight % IF_ALIGN_H) &&
+				    !(bdsIntHeight % BDS_ALIGN_H)) {
+					pipeConfigs.push_back({ bdsSF, { iif.width, ifHeight },
+								{ bdsWidth, bdsIntHeight }, gdc });
+				}
+			}
+
+			ifHeight -= IF_ALIGN_H;
+		}
+	}
+}
+
+void calculateBDS(ImgUDevice::Pipe *pipe, const Size &iif, const Size &gdc, float bdsSF)
+{
+	unsigned int minBDSWidth = gdc.width + FILTER_H * 2;
+
+	float sf = bdsSF;
+	while (sf <= BDS_SF_MAX && sf >= BDS_SF_MIN) {
+		float bdsWidth = static_cast<float>(iif.width) / sf;
+
+		if (std::fmod(bdsWidth, 1.0) == 0) {
+			unsigned int bdsIntWidth = static_cast<unsigned int>(bdsWidth);
+			if (!(bdsIntWidth % BDS_ALIGN_W) && bdsWidth >= minBDSWidth)
+				calculateBDSHeight(pipe, iif, gdc, bdsIntWidth, sf);
+		}
+
+		sf += BDS_SF_STEP;
+	}
+
+	sf = bdsSF;
+	while (sf <= BDS_SF_MAX && sf >= BDS_SF_MIN) {
+		float bdsWidth = static_cast<float>(iif.width) / sf;
+
+		if (std::fmod(bdsWidth, 1.0) == 0) {
+			unsigned int bdsIntWidth = static_cast<unsigned int>(bdsWidth);
+			if (!(bdsIntWidth % BDS_ALIGN_W) && bdsWidth >= minBDSWidth)
+				calculateBDSHeight(pipe, iif, gdc, bdsIntWidth, sf);
+		}
+
+		sf -= BDS_SF_STEP;
+	}
+}
+
+Size calculateGDC(ImgUDevice::Pipe *pipe)
+{
+	const Size &in = pipe->input;
+	const Size &main = pipe->main;
+	const Size &vf = pipe->viewfinder;
+	Size gdc;
+
+	if (!vf.isNull()) {
+		gdc.width = main.width;
+
+		float ratio = (main.width * vf.height) / static_cast<float>(vf.width);
+		gdc.height = std::max(static_cast<float>(main.height), ratio);
+
+		return gdc;
+	}
+
+	if (!isSameRatio(in, main)) {
+		gdc = main;
+		return gdc;
+	}
+
+	float totalSF = static_cast<float>(in.width) / main.width;
+	float bdsSF = totalSF > 2 ? 2 : 1;
+	float yuvSF = totalSF / bdsSF;
+	float sf = findScaleFactor(yuvSF, gdcScalingFactors);
+
+	gdc.width = main.width * sf;
+	gdc.height = main.height * sf;
+
+	return gdc;
+}
+
+FOV calcFOV(const Size &in, const ImgUDevice::PipeConfig &pipe)
+{
+	FOV fov{};
+
+	float inW = static_cast<float>(in.width);
+	float inH = static_cast<float>(in.height);
+	float ifCropW = static_cast<float>(in.width - pipe.iif.width);
+	float ifCropH = static_cast<float>(in.height - pipe.iif.height);
+	float gdcCropW = static_cast<float>(pipe.bds.width - pipe.gdc.width) * pipe.bds_sf;
+	float gdcCropH = static_cast<float>(pipe.bds.height - pipe.gdc.height) * pipe.bds_sf;
+
+	fov.w = (inW - (ifCropW + gdcCropW)) / inW;
+	fov.h = (inH - (ifCropH + gdcCropH)) / inH;
+
+	return fov;
+}
+
+} /* namespace */
+
+/**
+ * \struct PipeConfig
+ * \brief The ImgU pipe configuration parameters
+ *
+ * The ImgU image pipeline is composed of several hardware blocks that crop
+ * and scale the input image to obtain the desired output sizes. The
+ * scaling/cropping operations of those components is configured though the
+ * V4L2 selection API and the V4L2 subdev API applied to the ImgU media entity.
+ *
+ * The configurable components in the pipeline are:
+ * - IF: image feeder
+ * - BDS: bayer downscaler
+ * - GDC: geometric distorsion correction
+ *
+ * The IF crop rectangle is controlled by the V4L2_SEL_TGT_CROP selection target
+ * applied to the ImgU media entity sink pad number 0. The BDS scaler is
+ * controlled by the V4L2_SEL_TGT_COMPOSE target on the same pad, while the GDC
+ * output size is configured with the VIDIOC_SUBDEV_S_FMT IOCTL, again on pad
+ * number 0.
+ *
+ * The PipeConfig structure collects the sizes of each of those components
+ * plus the BDS scaling factor used to calculate the field of view
+ * of the final images.
+ */
+
+/**
+ * \struct Pipe
+ * \brief Describe the ImgU requested configuration
+ *
+ * The ImgU unit processes images through several components, which have
+ * to be properly configured inspecting the input image size and the desired
+ * output sizes. This structure collects the ImgU input configuration and the
+ * requested main output and viewfinder configurations.
+ *
+ * \var Pipe::input
+ * \brief The input image size
+ *
+ * \var Pipe::main
+ * \brief The requested main output size
+ *
+ * \var Pipe::viewfinder
+ * \brief The requested viewfinder output size
+ */
+
 /**
  * \brief Initialize components of the ImgU instance
  * \param[in] mediaDevice The ImgU instance media device
@@ -75,6 +373,63 @@ int ImgUDevice::init(MediaDevice *media, unsigned int index)
 }
 
 /**
+ * \brief Calculate the ImgU pipe configuration parameters
+ * \param[in] pipe The requested ImgU configuration
+ * \return An ImgUDevice::PipeConfig instance on success, an empty configuration
+ * otherwise
+ */
+ImgUDevice::PipeConfig ImgUDevice::calculatePipeConfig(Pipe *pipe)
+{
+	pipeConfigs.clear();
+
+	LOG(IPU3, Debug) << "Calculating pipe configuration for: ";
+	LOG(IPU3, Debug) << "input: " << pipe->input.toString();
+	LOG(IPU3, Debug) << "main: " << pipe->main.toString();
+	LOG(IPU3, Debug) << "vf: " << pipe->viewfinder.toString();
+
+	const Size &in = pipe->input;
+	Size gdc = calculateGDC(pipe);
+
+	unsigned int ifWidth = utils::alignUp(in.width, IF_ALIGN_W);
+	unsigned int ifHeight = in.height;
+	unsigned int minIfWidth = in.width - IF_CROP_MAX_W;
+	float bdsSF = static_cast<float>(in.width) / gdc.width;
+	float sf = findScaleFactor(bdsSF, bdsScalingFactors, true);
+
+	while (ifWidth >= minIfWidth) {
+		Size iif{ ifWidth, ifHeight };
+		calculateBDS(pipe, iif, gdc, sf);
+
+		ifWidth -= IF_ALIGN_W;
+	}
+
+	if (pipeConfigs.size() == 0) {
+		LOG(IPU3, Error) << "Failed to calculate pipe configuration";
+		return {};
+	}
+
+	FOV bestFov = calcFOV(pipe->input, pipeConfigs[0]);
+	unsigned int bestIndex = 0;
+	unsigned int p = 0;
+	for (auto pipeConfig : pipeConfigs) {
+		FOV fov = calcFOV(pipe->input, pipeConfig);
+		if (fov.isLarger(bestFov)) {
+			bestFov = fov;
+			bestIndex = p;
+		}
+
+		++p;
+	}
+
+	LOG(IPU3, Debug) << "Computed pipe configuration: ";
+	LOG(IPU3, Debug) << "IF: " << pipeConfigs[bestIndex].iif.toString();
+	LOG(IPU3, Debug) << "BDS: " << pipeConfigs[bestIndex].bds.toString();
+	LOG(IPU3, Debug) << "GDC: " << pipeConfigs[bestIndex].gdc.toString();
+
+	return pipeConfigs[bestIndex];
+}
+
+/**
  * \brief Configure the ImgU unit input
  * \param[in] size The ImgU input frame size
  * \param[in] inputFormat The format to be applied to ImgU input
diff --git a/src/libcamera/pipeline/ipu3/imgu.h b/src/libcamera/pipeline/ipu3/imgu.h
index 23ec1ca1..2f9dc022 100644
--- a/src/libcamera/pipeline/ipu3/imgu.h
+++ b/src/libcamera/pipeline/ipu3/imgu.h
@@ -23,8 +23,28 @@ struct StreamConfiguration;
 class ImgUDevice
 {
 public:
+	struct PipeConfig {
+		float bds_sf;
+		Size iif;
+		Size bds;
+		Size gdc;
+
+		bool isNull() const
+		{
+			return iif.isNull() || bds.isNull() || gdc.isNull();
+		}
+	};
+
+	struct Pipe {
+		Size input;
+		Size main;
+		Size viewfinder;
+	};
+
 	int init(MediaDevice *media, unsigned int index);
 
+	PipeConfig calculatePipeConfig(Pipe *pipe);
+
 	int configureInput(const Size &size, V4L2DeviceFormat *inputFormat);
 
 	int configureOutput(const StreamConfiguration &cfg,
diff --git a/src/libcamera/pipeline/ipu3/ipu3.cpp b/src/libcamera/pipeline/ipu3/ipu3.cpp
index a081a81c..c20ab3ab 100644
--- a/src/libcamera/pipeline/ipu3/ipu3.cpp
+++ b/src/libcamera/pipeline/ipu3/ipu3.cpp
@@ -314,7 +314,7 @@ CameraConfiguration *PipelineHandlerIPU3::generateConfiguration(Camera *camera,
 			 * to the ImgU  maximum output size) and aligned down to
 			 * the required frame margin.
 			 *
-			 * \todo Clarify the alignment constraints as exaplained
+			 * \todo Clarify the alignment constraints as explained
 			 * in validate()
 			 */
 			size = sensorResolution.boundedTo(IMGU_OUTPUT_MAX_SIZE);