libcamera: formats: Add planeSize() helpers to PixelFormatInfo

Add two helpers functions to the PixelFormatInfo class to compute the
byte size of a given plane, taking the frame size, the stride, the
alignment constraints and the vertical subsampling into account.

Use the new functions through the code base to replace manual
implementations.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Reviewed-by: Hirokazu Honda <hiroh@chromium.org>

include/libcamera/internal/formats.h

@@ -41,6 +41,10 @@ public:
 
 	unsigned int stride(unsigned int width, unsigned int plane,
 			    unsigned int align = 1) const;
+	unsigned int planeSize(const Size &size, unsigned int plane,
+			       unsigned int align = 1) const;
+	unsigned int planeSize(unsigned int height, unsigned int plane,
+			       unsigned int stride) const;
 	unsigned int frameSize(const Size &size, unsigned int align = 1) const;
 	unsigned int frameSize(const Size &size,
 			       const std::array<unsigned int, 3> &strides) const;

src/android/mm/generic_camera_buffer.cpp

@@ -107,16 +107,9 @@ CameraBuffer::Private::Private([[maybe_unused]] CameraBuffer *cameraBuffer,
 
 	unsigned int offset = 0;
 	for (unsigned int i = 0; i < numPlanes; ++i) {
-		/*
+		const unsigned int planeSize = info.planeSize(size, i);
-		 * \todo Remove if this plane size computation function is
-		 * added to PixelFormatInfo.
-		 */
-		const unsigned int vertSubSample = info.planes[i].verticalSubSampling;
-		const unsigned int stride = info.stride(size.width, i, 1u);
-		const unsigned int planeSize =
-			stride * ((size.height + vertSubSample - 1) / vertSubSample);
 
-		planeInfo_[i].stride = stride;
+		planeInfo_[i].stride = info.stride(size.width, i, 1u);
 		planeInfo_[i].offset = offset;
 		planeInfo_[i].size = planeSize;
 

src/android/yuv/post_processor_yuv.cpp

@@ -134,11 +134,9 @@ void PostProcessorYuv::calculateLengths(const StreamConfiguration &inCfg,
 		sourceStride_[i] = inCfg.stride;
 		destinationStride_[i] = nv12Info.stride(destinationSize_.width, i, 1);
 
-		const unsigned int vertSubSample =
+		sourceLength_[i] = nv12Info.planeSize(sourceSize_.height, i,
-			nv12Info.planes[i].verticalSubSampling;
+						      sourceStride_[i]);
-		sourceLength_[i] = sourceStride_[i] *
+		destinationLength_[i] = nv12Info.planeSize(destinationSize_.height, i,
-			((sourceSize_.height + vertSubSample - 1) / vertSubSample);
+							   destinationStride_[i]);
-		destinationLength_[i] = destinationStride_[i] *
-			((destinationSize_.height + vertSubSample - 1) / vertSubSample);
 	}
 }

src/libcamera/formats.cpp

@@ -11,6 +11,7 @@
 #include <errno.h>
 
 #include <libcamera/base/log.h>
+#include <libcamera/base/utils.h>
 
 #include <libcamera/formats.h>
 
@@ -800,33 +801,81 @@ unsigned int PixelFormatInfo::stride(unsigned int width, unsigned int plane,
 	return (stride + align - 1) / align * align;
 }
 
+/**
+ * \brief Compute the number of bytes necessary to store a plane of a frame
+ * \param[in] size The size of the frame, in pixels
+ * \param[in] plane The plane index
+ * \param[in] align The stride alignment, in bytes (1 for default alignment)
+ *
+ * The plane size is computed by multiplying the line stride and the frame
+ * height, taking subsampling and other format characteristics into account.
+ * Stride alignment constraints may be specified through the \a align parameter.
+ *
+ * \sa stride()
+ *
+ * \return The number of bytes necessary to store the plane, or 0 if the
+ * PixelFormatInfo instance is not valid or the plane number isn't valid for the
+ * format
+ */
+unsigned int PixelFormatInfo::planeSize(const Size &size, unsigned int plane,
+					unsigned int align) const
+{
+	unsigned int stride = PixelFormatInfo::stride(size.width, plane, align);
+	if (!stride)
+		return 0;
+
+	return planeSize(size.height, plane, stride);
+}
+
+/**
+ * \brief Compute the number of bytes necessary to store a plane of a frame
+ * \param[in] height The height of the frame, in pixels
+ * \param[in] plane The plane index
+ * \param[in] stride The plane stride, in bytes
+ *
+ * The plane size is computed by multiplying the line stride and the frame
+ * height, taking subsampling and other format characteristics into account.
+ * Stride alignment constraints may be specified through the \a align parameter.
+ *
+ * \return The number of bytes necessary to store the plane, or 0 if the
+ * PixelFormatInfo instance is not valid or the plane number isn't valid for the
+ * format
+ */
+unsigned int PixelFormatInfo::planeSize(unsigned int height, unsigned int plane,
+					unsigned int stride) const
+{
+	unsigned int vertSubSample = planes[plane].verticalSubSampling;
+	if (!vertSubSample)
+		return 0;
+
+	/* stride * ceil(height / verticalSubSampling) */
+	return stride * ((height + vertSubSample - 1) / vertSubSample);
+}
+
 /**
  * \brief Compute the number of bytes necessary to store a frame
  * \param[in] size The size of the frame, in pixels
  * \param[in] align The stride alignment, in bytes (1 for default alignment)
  *
- * The frame is computed by adding the product of the line stride and the frame
+ * The frame size is computed by adding the size of all planes, as computed by
- * height for all planes, taking subsampling and other format characteristics
+ * planeSize(), using the specified alignment constraints for all planes. For
- * into account. Additional stride alignment constraints may be specified
+ * more complex stride constraints, use the frameSize() overloaded version that
- * through the \a align parameter, and will apply to all planes. For more
+ * takes an array of stride values.
- * complex stride constraints, use the frameSize() overloaded version that takes
- * an array of stride values.
  *
- * \sa stride()
+ * \sa planeSize()
  *
  * \return The number of bytes necessary to store the frame, or 0 if the
  * PixelFormatInfo instance is not valid
  */
 unsigned int PixelFormatInfo::frameSize(const Size &size, unsigned int align) const
 {
-	/* stride * ceil(height / verticalSubSampling) */
 	unsigned int sum = 0;
-	for (unsigned int i = 0; i < 3; i++) {
+
-		unsigned int vertSubSample = planes[i].verticalSubSampling;
+	for (const auto &[i, plane] : utils::enumerate(planes)) {
-		if (!vertSubSample)
+		if (plane.bytesPerGroup == 0)
-			continue;
+			break;
-		sum += stride(size.width, i, align)
+
-		     * ((size.height + vertSubSample - 1) / vertSubSample);
+		sum += planeSize(size, i, align);
 	}
 
 	return sum;

src/libcamera/v4l2_videodevice.cpp

@@ -1337,11 +1337,7 @@ std::unique_ptr<FrameBuffer> V4L2VideoDevice::createBuffer(unsigned int index)
 			planes[i].offset = offset;
 
 			/* \todo Take the V4L2 stride into account */
-			const unsigned int vertSubSample =
+			planes[i].length = info.planeSize(format_.size, i);
-				info.planes[i].verticalSubSampling;
-			planes[i].length =
-				info.stride(format_.size.width, i, 1u) *
-				((format_.size.height + vertSubSample - 1) / vertSubSample);
 			offset += planes[i].length;
 		}
 	}