libcamera: pipeline: simple: converter: Add scaling support

Extend the SimpleConverter to support scaling, with reporting of the
minimum and maximum output sizes supported for a given input size.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Niklas Söderlund <niklas.soderlund@ragnatech.se>

src/libcamera/pipeline/simple/converter.cpp

@@ -8,6 +8,7 @@
 #include "converter.h"
 
 #include <algorithm>
+#include <limits.h>
 
 #include <libcamera/buffer.h>
 #include <libcamera/geometry.h>
@@ -93,7 +94,52 @@ std::vector<PixelFormat> SimpleConverter::formats(PixelFormat input)
 	return pixelFormats;
 }
 
-int SimpleConverter::configure(PixelFormat inputFormat,
+SizeRange SimpleConverter::sizes(const Size &input)
+{
+	if (!m2m_)
+		return {};
+
+	/*
+	 * Set the size on the input side (V4L2 output) of the converter to
+	 * enumerate the scaling capabilities on its output (V4L2 capture).
+	 */
+	V4L2DeviceFormat format;
+	format.fourcc = V4L2PixelFormat();
+	format.size = input;
+
+	int ret = m2m_->output()->setFormat(&format);
+	if (ret < 0) {
+		LOG(SimplePipeline, Error)
+			<< "Failed to set format: " << strerror(-ret);
+		return {};
+	}
+
+	SizeRange sizes;
+
+	format.size = { 1, 1 };
+	ret = m2m_->capture()->setFormat(&format);
+	if (ret < 0) {
+		LOG(SimplePipeline, Error)
+			<< "Failed to set format: " << strerror(-ret);
+		return {};
+	}
+
+	sizes.min = format.size;
+
+	format.size = { UINT_MAX, UINT_MAX };
+	ret = m2m_->capture()->setFormat(&format);
+	if (ret < 0) {
+		LOG(SimplePipeline, Error)
+			<< "Failed to set format: " << strerror(-ret);
+		return {};
+	}
+
+	sizes.max = format.size;
+
+	return sizes;
+}
+
+int SimpleConverter::configure(PixelFormat inputFormat, const Size &inputSize,
 			       StreamConfiguration *cfg)
 {
 	V4L2DeviceFormat format;
@@ -101,7 +147,7 @@ int SimpleConverter::configure(PixelFormat inputFormat,
 
 	V4L2PixelFormat videoFormat = m2m_->output()->toV4L2PixelFormat(inputFormat);
 	format.fourcc = videoFormat;
-	format.size = cfg->size;
+	format.size = inputSize;
 
 	ret = m2m_->output()->setFormat(&format);
 	if (ret < 0) {
@@ -110,18 +156,16 @@ int SimpleConverter::configure(PixelFormat inputFormat,
 		return ret;
 	}
 
-	if (format.fourcc != videoFormat || format.size != cfg->size) {
+	if (format.fourcc != videoFormat || format.size != inputSize) {
 		LOG(SimplePipeline, Error)
 			<< "Input format not supported";
 		return -EINVAL;
 	}
 
-	/*
+	/* Set the pixel format and size on the output. */
-	 * Set the pixel format on the output, the size is identical to the
-	 * input as we don't support scaling.
-	 */
 	videoFormat = m2m_->capture()->toV4L2PixelFormat(cfg->pixelFormat);
 	format.fourcc = videoFormat;
+	format.size = cfg->size;
 
 	ret = m2m_->capture()->setFormat(&format);
 	if (ret < 0) {

src/libcamera/pipeline/simple/converter.h

@@ -20,6 +20,7 @@ namespace libcamera {
 class FrameBuffer;
 class MediaDevice;
 struct Size;
+class SizeRange;
 struct StreamConfiguration;
 class V4L2M2MDevice;
 
@@ -33,8 +34,10 @@ public:
 	void close();
 
 	std::vector<PixelFormat> formats(PixelFormat input);
+	SizeRange sizes(const Size &input);
 
-	int configure(PixelFormat inputFormat, StreamConfiguration *cfg);
+	int configure(PixelFormat inputFormat, const Size &inputSize,
+		      StreamConfiguration *cfg);
 	int exportBuffers(unsigned int count,
 			  std::vector<std::unique_ptr<FrameBuffer>> *buffers);
 

src/libcamera/pipeline/simple/simple.cpp

@@ -555,7 +555,8 @@ int SimplePipelineHandler::configure(Camera *camera, CameraConfiguration *c)
 	useConverter_ = config->needConversion();
 
 	if (useConverter_) {
-		int ret = converter_->configure(pipeConfig.pixelFormat, &cfg);
+		int ret = converter_->configure(pipeConfig.pixelFormat,
+						cfg.size, &cfg);
 		if (ret < 0) {
 			LOG(SimplePipeline, Error)
 				<< "Unable to configure converter";