[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 17:09:43 CEST 2022
Another comment.
On Thu, Aug 25, 2022 at 02:05:57AM +0300, Laurent Pinchart via libcamera-devel wrote:
> 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
> > */
The documentation needs to be updated with the new parameter.
> > 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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