[libcamera-devel] [PATCH v3 2/2] pipeline: raspberrypi: Fix handling of colour spaces

[David Plowman]

We implement a custom validateColorSpaces method that forces all
(non-raw) streams to same colour space, whilst distinguishing RGB
streams from YUV ones, as the former must have the YCbCr encoding and
range over-written.

When we apply the colour space, we always send the full YUV version as
that gets converted correctly to what our hardware drivers expect. It
is also careful to check what comes back as the YCbCr information gets
overwritten again on the way back.

Signed-off-by: David Plowman <david.plowman at raspberrypi.com>
Reviewed-by: Naushir Patuck <naush at raspberrypi.com>
---
 .../pipeline/raspberrypi/raspberrypi.cpp      | 99 ++++++++++++++++++-
 1 file changed, 98 insertions(+), 1 deletion(-)

diff --git a/src/libcamera/pipeline/raspberrypi/raspberrypi.cpp b/src/libcamera/pipeline/raspberrypi/raspberrypi.cpp
index 8569df17..135024e7 100644
--- a/src/libcamera/pipeline/raspberrypi/raspberrypi.cpp
+++ b/src/libcamera/pipeline/raspberrypi/raspberrypi.cpp
@@ -310,6 +310,7 @@ class RPiCameraConfiguration : public CameraConfiguration
 public:
 	RPiCameraConfiguration(const RPiCameraData *data);
 
+	CameraConfiguration::Status validateColorSpaces(ColorSpaceFlags flags);
 	Status validate() override;
 
 	/* Cache the combinedTransform_ that will be applied to the sensor */
@@ -317,6 +318,13 @@ public:
 
 private:
 	const RPiCameraData *data_;
+
+	/*
+	 * Store the colour spaces that all our streams will have. RGB format streams
+	 * will be the same but need the YCbCr fields cleared.
+	 */
+	std::optional<ColorSpace> yuvColorSpace_;
+	std::optional<ColorSpace> rgbColorSpace_;
 };
 
 class PipelineHandlerRPi : public PipelineHandler
@@ -357,6 +365,89 @@ RPiCameraConfiguration::RPiCameraConfiguration(const RPiCameraData *data)
 {
 }
 
+static const std::vector<ColorSpace> validColorSpaces = {
+	ColorSpace::Sycc,
+	ColorSpace::Smpte170m,
+	ColorSpace::Rec709
+};
+
+static std::optional<ColorSpace> findValidColorSpace(const ColorSpace &colourSpace)
+{
+	for (auto cs : validColorSpaces) {
+		if (colourSpace.primaries == cs.primaries &&
+		    colourSpace.transferFunction == cs.transferFunction)
+			return cs;
+	}
+
+	return std::nullopt;
+}
+
+static bool isRgb(const PixelFormat &pixFmt)
+{
+	const PixelFormatInfo &info = PixelFormatInfo::info(pixFmt);
+	return info.colourEncoding == PixelFormatInfo::ColourEncodingRGB;
+}
+
+static bool isYuv(const PixelFormat &pixFmt)
+{
+	/* The code below would return true for raw mono streams, so weed those out first. */
+	if (isRaw(pixFmt))
+		return false;
+
+	const PixelFormatInfo &info = PixelFormatInfo::info(pixFmt);
+	return info.colourEncoding == PixelFormatInfo::ColourEncodingYUV;
+}
+
+CameraConfiguration::Status RPiCameraConfiguration::validateColorSpaces([[maybe_unused]] ColorSpaceFlags flags)
+{
+	Status status = Valid;
+	yuvColorSpace_.reset();
+
+	for (auto cfg : config_) {
+		/* First fix up raw streams to have the "raw" colour space. */
+		if (isRaw(cfg.pixelFormat) && cfg.colorSpace != ColorSpace::Raw) {
+			/* If there was no value here, that doesn't count as "adjusted". */
+			if (cfg.colorSpace)
+				status = Adjusted;
+			cfg.colorSpace = ColorSpace::Raw;
+		}
+
+		/* Next we need to find our shared colour space. The first valid one will do. */
+		if (cfg.colorSpace && cfg.colorSpace != ColorSpace::Raw && !yuvColorSpace_)
+			yuvColorSpace_ = findValidColorSpace(cfg.colorSpace.value());
+	}
+
+	/* If no colour space was given anywhere, choose sYCC. */
+	if (!yuvColorSpace_)
+		yuvColorSpace_ = ColorSpace::Sycc;
+
+	/* Note the version of this that any RGB streams will have to use. */
+	rgbColorSpace_ = yuvColorSpace_;
+	rgbColorSpace_->ycbcrEncoding = ColorSpace::YcbcrEncoding::None;
+	rgbColorSpace_->range = ColorSpace::Range::Full;
+
+	/* Go through the streams again and force everyone to the same colour space. */
+	for (auto cfg : config_) {
+		if (cfg.colorSpace == ColorSpace::Raw)
+			continue;
+
+		if (isYuv(cfg.pixelFormat) && cfg.colorSpace != yuvColorSpace_) {
+			/* Again, no value means "not adjusted". */
+			if (cfg.colorSpace)
+				status = Adjusted;
+			cfg.colorSpace = yuvColorSpace_;
+		}
+		if (isRgb(cfg.pixelFormat) && cfg.colorSpace != rgbColorSpace_) {
+			/* Be nice, and let the YUV version count as non-adjusted too. */
+			if (cfg.colorSpace && cfg.colorSpace != yuvColorSpace_)
+				status = Adjusted;
+			cfg.colorSpace = rgbColorSpace_;
+		}
+	}
+
+	return status;
+}
+
 CameraConfiguration::Status RPiCameraConfiguration::validate()
 {
 	Status status = Valid;
@@ -533,7 +624,8 @@ CameraConfiguration::Status RPiCameraConfiguration::validate()
 		V4L2DeviceFormat format;
 		format.fourcc = dev->toV4L2PixelFormat(cfg.pixelFormat);
 		format.size = cfg.size;
-		format.colorSpace = cfg.colorSpace;
+		/* We want to send the associated YCbCr info through to the driver. */
+		format.colorSpace = yuvColorSpace_;
 
 		LOG(RPI, Debug)
 			<< "Try color space " << ColorSpace::toString(cfg.colorSpace);
@@ -542,6 +634,11 @@ CameraConfiguration::Status RPiCameraConfiguration::validate()
 		if (ret)
 			return Invalid;
 
+		/*
+		 * But for RGB streams, the YCbCr info gets overwritten on the way back
+		 * so we must check against what the stream cfg says, not what we actually
+		 * requested (which carefully included the YCbCr info)!
+		 */
 		if (cfg.colorSpace != format.colorSpace) {
 			status = Adjusted;
 			LOG(RPI, Debug)
-- 
2.30.2