[libcamera-devel] [PATCH v2 2/6] libcamera: v4l2_device: Adjust colorspace if pixel format is RGB
Laurent Pinchart
laurent.pinchart at ideasonboard.com
Thu Aug 25 01:05:57 CEST 2022
Hi Umang,
Thank you for the patch.
On Wed, Aug 24, 2022 at 09:54:21PM +0530, Umang Jain via libcamera-devel wrote:
> The V4L2_COLORSPACE_SRGB colorspace maps to ColorSpace::Srgb.
> This is wrong as the V4L2_COLORSPACE_SRGB is ill-defined (defines
> Rec 601 Y'CbCr encoding and limited range) in the kernel.
>
> The RGB pixel formats should not use any Y'CbCr encoding and is always
> full range. Adjust the colorspace before reporting back to the
> userspace in such a situation.
>
> Moving forwards, the ColorSpace::Srgb will be defined in the true sense
> for RGB pixel formats.
Mentioning sRGB here is a bit confusing I think. Let's focus on what
this patch does (and this will also help making sure I understood this
correctly):
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 at ideasonboard.com>
> ---
> include/libcamera/internal/v4l2_device.h | 5 ++++-
> src/libcamera/v4l2_device.cpp | 19 +++++++++++++++----
> src/libcamera/v4l2_subdevice.cpp | 10 ++++++++--
> src/libcamera/v4l2_videodevice.cpp | 12 ++++++++----
> 4 files changed, 35 insertions(+), 11 deletions(-)
>
> diff --git a/include/libcamera/internal/v4l2_device.h b/include/libcamera/internal/v4l2_device.h
> index a52a5f2c..5ae2ef8a 100644
> --- a/include/libcamera/internal/v4l2_device.h
> +++ b/include/libcamera/internal/v4l2_device.h
> @@ -22,6 +22,8 @@
> #include <libcamera/color_space.h>
> #include <libcamera/controls.h>
>
> +#include "libcamera/internal/formats.h"
> +
> namespace libcamera {
>
> class EventNotifier;
> @@ -59,7 +61,8 @@ protected:
> int fd() const { return fd_.get(); }
>
> template<typename T>
> - static std::optional<ColorSpace> toColorSpace(const T &v4l2Format);
> + static std::optional<ColorSpace> toColorSpace(const T &v4l2Format,
> + const PixelFormatInfo::ColourEncoding &colourEncoding);
PixelFormatInfo::ColourEncoding colourEncoding);
Same below.
>
> template<typename T>
> static int fromColorSpace(const std::optional<ColorSpace> &colorSpace, T &v4l2Format);
> diff --git a/src/libcamera/v4l2_device.cpp b/src/libcamera/v4l2_device.cpp
> index b22a981f..1fb08b9d 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"
>
> /**
> @@ -816,7 +817,8 @@ 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,
> + const PixelFormatInfo::ColourEncoding &colourEncoding)
> {
> auto itColor = v4l2ToColorSpace.find(v4l2Format.colorspace);
> if (itColor == v4l2ToColorSpace.end())
> @@ -839,6 +841,9 @@ std::optional<ColorSpace> V4L2Device::toColorSpace(const T &v4l2Format)
> return std::nullopt;
>
> colorSpace.ycbcrEncoding = itYcbcrEncoding->second;
> +
I'd add a comment here, or we'll forget why.
/*
* 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::ColourEncodingRGB)
Shouldn't this be
if (colourEncoding != PixelFormatInfo::ColourEncodingYUV)
? Raw formats have no YCbCr encoding either. The subject line would need
to be updated accordingly, I'd write "Adjust colorspace based on pixel
format".
> + colorSpace.ycbcrEncoding = ColorSpace::YcbcrEncoding::None;
> }
>
> if (v4l2Format.quantization != V4L2_QUANTIZATION_DEFAULT) {
> @@ -847,14 +852,20 @@ std::optional<ColorSpace> V4L2Device::toColorSpace(const T &v4l2Format)
> return std::nullopt;
>
> colorSpace.range = itRange->second;
> +
> + if (colourEncoding == PixelFormatInfo::ColourEncodingRGB)
Same here.
> + 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 &,
> + const PixelFormatInfo::ColourEncoding &);
> +template std::optional<ColorSpace> V4L2Device::toColorSpace(const struct v4l2_pix_format_mplane &,
> + const PixelFormatInfo::ColourEncoding &);
> +template std::optional<ColorSpace> V4L2Device::toColorSpace(const struct v4l2_mbus_framefmt &,
> + const PixelFormatInfo::ColourEncoding &);
>
> /**
> * \brief Fill in the color space fields of a V4L2 format from a ColorSpace
> diff --git a/src/libcamera/v4l2_subdevice.cpp b/src/libcamera/v4l2_subdevice.cpp
> index ab74b9f0..a52c414f 100644
> --- a/src/libcamera/v4l2_subdevice.cpp
> +++ b/src/libcamera/v4l2_subdevice.cpp
> @@ -502,7 +502,10 @@ int V4L2Subdevice::getFormat(unsigned int pad, V4L2SubdeviceFormat *format,
> format->size.width = subdevFmt.format.width;
> format->size.height = subdevFmt.format.height;
> format->mbus_code = subdevFmt.format.code;
> - format->colorSpace = toColorSpace(subdevFmt.format);
> + auto iter = formatInfoMap.find(format->mbus_code);
> + if (iter == formatInfoMap.end())
> + return -EINVAL;
That seems a bit harsh. I'm thinking about the simple pipeline handler
in particular, which will propagate media bus formats through the
pipeline without caring much about the format itself. Would it better to
instead pick a default ?
> + format->colorSpace = toColorSpace(subdevFmt.format, iter->second.colourEncoding);
>
> return 0;
> }
> @@ -548,7 +551,10 @@ int V4L2Subdevice::setFormat(unsigned int pad, V4L2SubdeviceFormat *format,
> format->size.width = subdevFmt.format.width;
> format->size.height = subdevFmt.format.height;
> format->mbus_code = subdevFmt.format.code;
> - format->colorSpace = toColorSpace(subdevFmt.format);
> + auto iter = formatInfoMap.find(format->mbus_code);
> + if (iter == formatInfoMap.end())
> + return -EINVAL;
Same here.
> + format->colorSpace = toColorSpace(subdevFmt.format, iter->second.colourEncoding);
>
> return 0;
> }
> diff --git a/src/libcamera/v4l2_videodevice.cpp b/src/libcamera/v4l2_videodevice.cpp
> index 5a2d0e5b..0e3f5436 100644
> --- a/src/libcamera/v4l2_videodevice.cpp
> +++ b/src/libcamera/v4l2_videodevice.cpp
> @@ -931,7 +931,8 @@ int V4L2VideoDevice::getFormatMultiplane(V4L2DeviceFormat *format)
I'm tempted to add a helper just above this function:
namespace {
std::optional<ColorSpace> toColorSpace(const struct v4l2_pix_format_mplane &pix)
{
V4L2PixelFormat fourcc{ pix.pixelformat };
return toColorSpace(pix, PixelFormatInfo::info(fourcc).colourEncoding);
}
} /* namespace */
to make the color below a bit nicer (it would actually not need to be
changed at all). Up to you.
> format->size.height = pix->height;
> format->fourcc = V4L2PixelFormat(pix->pixelformat);
> format->planesCount = pix->num_planes;
> - format->colorSpace = toColorSpace(*pix);
> + format->colorSpace =
> + toColorSpace(*pix, PixelFormatInfo::info(format->fourcc).colourEncoding);
>
> for (unsigned int i = 0; i < format->planesCount; ++i) {
> format->planes[i].bpl = pix->plane_fmt[i].bytesperline;
> @@ -987,7 +988,8 @@ int V4L2VideoDevice::trySetFormatMultiplane(V4L2DeviceFormat *format, bool set)
> format->planes[i].bpl = pix->plane_fmt[i].bytesperline;
> format->planes[i].size = pix->plane_fmt[i].sizeimage;
> }
> - format->colorSpace = toColorSpace(*pix);
> + format->colorSpace =
> + toColorSpace(*pix, PixelFormatInfo::info(format->fourcc).colourEncoding);
>
> return 0;
> }
> @@ -1011,7 +1013,8 @@ int V4L2VideoDevice::getFormatSingleplane(V4L2DeviceFormat *format)
> format->planesCount = 1;
> format->planes[0].bpl = pix->bytesperline;
> format->planes[0].size = pix->sizeimage;
> - format->colorSpace = toColorSpace(*pix);
> + format->colorSpace =
> + toColorSpace(*pix, PixelFormatInfo::info(format->fourcc).colourEncoding);
>
> return 0;
> }
> @@ -1053,7 +1056,8 @@ int V4L2VideoDevice::trySetFormatSingleplane(V4L2DeviceFormat *format, bool set)
> format->planesCount = 1;
> format->planes[0].bpl = pix->bytesperline;
> format->planes[0].size = pix->sizeimage;
> - format->colorSpace = toColorSpace(*pix);
> + format->colorSpace =
> + toColorSpace(*pix, PixelFormatInfo::info(format->fourcc).colourEncoding);
>
> return 0;
> }
--
Regards,
Laurent Pinchart
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