Add lcameraBuff Stage 2 plugin with YUV attach and unit tests.

Introduce params parsing, pixel/format decisions, capture layout, shared
YuvStimProducer per camera, and channel stimulus buffers with attach flow.

Co-authored-by: Cursor <cursoragent@cursor.com>

stimBuffApis/lcameraBuff/pixelAndColorFormatDecisions.cpp

@@ -0,0 +1,141 @@
+#include <pixelAndColorFormatDecisions.h>
+#include <algorithm>
+#include <cctype>
+#include <stdexcept>
+#include <string>
+#include <unordered_set>
+
+namespace smo {
+namespace stim_buff {
+namespace lcamera_buff {
+
+namespace {
+
+std::string normalizeFourccToken(std::string token)
+{
+	for (char& character : token)
+	{
+		character = static_cast<char>(
+			std::toupper(static_cast<unsigned char>(character)));
+	}
+
+	return token;
+}
+
+bool fourccInSet(
+	const std::string& fourcc,
+	const std::unordered_set<std::string>& candidates)
+{
+	return candidates.find(fourcc) != candidates.end();
+}
+
+const std::unordered_set<std::string>& yuv420FourccSet()
+{
+	static const std::unordered_set<std::string> fourccs = {
+		"YU12", "YV12", "YUV420", "YVU420", "NV12", "NV21",
+	};
+	return fourccs;
+}
+
+const std::unordered_set<std::string>& yuv422FourccSet()
+{
+	static const std::unordered_set<std::string> fourccs = {
+		"YUYV", "YVYU", "UYVY", "VYUY", "YUV422", "YVU422",
+		"NV16", "NV61", "YU16", "YV16",
+	};
+	return fourccs;
+}
+
+const std::unordered_set<std::string>& yuv444FourccSet()
+{
+	static const std::unordered_set<std::string> fourccs = {
+		"YUV444", "YVU444",
+	};
+	return fourccs;
+}
+
+unsigned chromaPlaneWidth(unsigned frameWidth, YuvChromaSubsampling subsampling)
+{
+	switch (subsampling)
+	{
+		case YuvChromaSubsampling::Yuv420:
+		case YuvChromaSubsampling::Yuv422:
+			return (frameWidth + 1u) / 2u;
+
+		case YuvChromaSubsampling::Yuv444:
+			return frameWidth;
+	}
+
+	throw std::logic_error(
+		"lcameraBuff: unhandled YuvChromaSubsampling in chromaPlaneWidth");
+}
+
+unsigned chromaPlaneHeight(unsigned frameHeight, YuvChromaSubsampling subsampling)
+{
+	switch (subsampling)
+	{
+		case YuvChromaSubsampling::Yuv420:
+			return (frameHeight + 1u) / 2u;
+
+		case YuvChromaSubsampling::Yuv422:
+		case YuvChromaSubsampling::Yuv444:
+			return frameHeight;
+	}
+
+	throw std::logic_error(
+		"lcameraBuff: unhandled YuvChromaSubsampling in chromaPlaneHeight");
+}
+
+} // namespace
+
+YuvChromaSubsampling classifyYuvChromaSubsampling(
+	const lcamera_dev::LcameraDevConfiguredCameraMode& configuredMode)
+{
+	const std::string fourcc =
+		normalizeFourccToken(configuredMode.pixelFormatName);
+
+	if (fourccInSet(fourcc, yuv420FourccSet())) {
+		return YuvChromaSubsampling::Yuv420;
+	}
+
+	if (fourccInSet(fourcc, yuv422FourccSet())) {
+		return YuvChromaSubsampling::Yuv422;
+	}
+
+	if (fourccInSet(fourcc, yuv444FourccSet())) {
+		return YuvChromaSubsampling::Yuv444;
+	}
+
+	throw std::runtime_error(
+		"lcameraBuff: unsupported YUV pixel format for chroma geometry: "
+		+ configuredMode.pixelFormatName);
+}
+
+size_t computeDeinterleavedChannelByteSize(
+	YuvChannelKind channel,
+	unsigned width, unsigned height,
+	YuvChromaSubsampling subsampling)
+{
+	switch (channel)
+	{
+		case YuvChannelKind::Y:
+			return static_cast<size_t>(width) * static_cast<size_t>(height);
+
+		case YuvChannelKind::U:
+		case YuvChannelKind::V:
+		{
+			const unsigned chromaWidth = chromaPlaneWidth(width, subsampling);
+			const unsigned chromaHeight =
+				chromaPlaneHeight(height, subsampling);
+			return static_cast<size_t>(chromaWidth)
+				* static_cast<size_t>(chromaHeight);
+		}
+	}
+
+	throw std::logic_error(
+		"lcameraBuff: unhandled YuvChannelKind in computeDeinterleavedChannelByteSize");
+}
+
+} // namespace lcamera_buff
+} // namespace stim_buff
+} // namespace smo