libcamera: v4l2_device: Adjust colorspace based on pixel format

V4L2 has no "none" YCbCr encoding, and thus reports an encoding for all
formats, including RGB and raw formats. This causes the libcamera
ColorSpace to report incorrect encodings for non-YUV formats. Fix it by
overriding the encoding reported by the kernel to YCbCrEncoding::None
for non-YUV pixel formats and media bus formats.

Similarly, override the quantization range of non-YUV formats to full
range, as limited range isn't used for RGB and raw formats.

Signed-off-by: Umang Jain <umang.jain@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Paul Elder <paul.elder@ideasonboard.com>

1 files changed, 25 insertions, 4 deletions

diff --git a/src/libcamera/v4l2_device.cpp b/src/libcamera/v4l2_device.cpp
index b22a981f..301620f8 100644
--- a/src/libcamera/v4l2_device.cpp
+++ b/src/libcamera/v4l2_device.cpp
@@ -24,6 +24,7 @@
 #include <libcamera/base/log.h>
 #include <libcamera/base/utils.h>
 
+#include "libcamera/internal/formats.h"
 #include "libcamera/internal/sysfs.h"
 
 /**
@@ -805,6 +806,7 @@ static const std::map<ColorSpace::Range, v4l2_quantization> rangeToV4l2 = {
 /**
  * \brief Convert the color space fields in a V4L2 format to a ColorSpace
  * \param[in] v4l2Format A V4L2 format containing color space information
+ * \param[in] colourEncoding Type of colour encoding
  *
  * The colorspace, ycbcr_enc, xfer_func and quantization fields within a
  * V4L2 format structure are converted to a corresponding ColorSpace.
@@ -816,7 +818,8 @@ static const std::map<ColorSpace::Range, v4l2_quantization> rangeToV4l2 = {
  * \retval std::nullopt One or more V4L2 color space fields were not recognised
  */
 template<typename T>
-std::optional<ColorSpace> V4L2Device::toColorSpace(const T &v4l2Format)
+std::optional<ColorSpace> V4L2Device::toColorSpace(const T &v4l2Format,
+						   PixelFormatInfo::ColourEncoding colourEncoding)
 {
 	auto itColor = v4l2ToColorSpace.find(v4l2Format.colorspace);
 	if (itColor == v4l2ToColorSpace.end())
@@ -839,6 +842,14 @@ std::optional<ColorSpace> V4L2Device::toColorSpace(const T &v4l2Format)
 			return std::nullopt;
 
 		colorSpace.ycbcrEncoding = itYcbcrEncoding->second;
+
+		/*
+		 * V4L2 has no "none" encoding, override the value returned by
+		 * the kernel for non-YUV formats as YCbCr encoding isn't
+		 * applicable in that case.
+		 */
+		if (colourEncoding != PixelFormatInfo::ColourEncodingYUV)
+			colorSpace.ycbcrEncoding = ColorSpace::YcbcrEncoding::None;
 	}
 
 	if (v4l2Format.quantization != V4L2_QUANTIZATION_DEFAULT) {
@@ -847,14 +858,24 @@ std::optional<ColorSpace> V4L2Device::toColorSpace(const T &v4l2Format)
 			return std::nullopt;
 
 		colorSpace.range = itRange->second;
+
+		/*
+		 * "Limited" quantization range is only meant for YUV formats.
+		 * Override the range to "Full" for all other formats.
+		 */
+		if (colourEncoding != PixelFormatInfo::ColourEncodingYUV)
+			colorSpace.range = ColorSpace::Range::Full;
 	}
 
 	return colorSpace;
 }
 
-template std::optional<ColorSpace> V4L2Device::toColorSpace(const struct v4l2_pix_format &);
-template std::optional<ColorSpace> V4L2Device::toColorSpace(const struct v4l2_pix_format_mplane &);
-template std::optional<ColorSpace> V4L2Device::toColorSpace(const struct v4l2_mbus_framefmt &);
+template std::optional<ColorSpace> V4L2Device::toColorSpace(const struct v4l2_pix_format &,
+							    PixelFormatInfo::ColourEncoding);
+template std::optional<ColorSpace> V4L2Device::toColorSpace(const struct v4l2_pix_format_mplane &,
+							    PixelFormatInfo::ColourEncoding);
+template std::optional<ColorSpace> V4L2Device::toColorSpace(const struct v4l2_mbus_framefmt &,
+							    PixelFormatInfo::ColourEncoding);
 
 /**
  * \brief Fill in the color space fields of a V4L2 format from a ColorSpace