[libcamera-devel] [PATCH v2 2/6] libcamera: v4l2_device: Adjust colorspace if pixel format is RGB
Laurent Pinchart
laurent.pinchart at ideasonboard.com
Fri Aug 26 15:23:09 CEST 2022
Hi Umang,
On Fri, Aug 26, 2022 at 11:46:58AM +0530, Umang Jain wrote:
> On 8/25/22 4:35 AM, Laurent Pinchart wrote:
> > 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.
>
> Correct.
>
> > Similarly, override the quantization range of non-YUV formats to full
> > range, as limited range isn't used for RGB and raw formats.
>
> Seems correct too, I agree my commit message was not at it's best.
>
> >> 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 ?
>
> I wasn't aware of that. I assumed (formatInfoMap.find(format->mbus_code)
> == formatInfoMap.end()) would be very hard to trigger and if it does at
> all, we want to fail loudly.
Currently, we only use formatInfoMap in two places:
- in V4L2SubdeviceFormat::bitsPerPixel()
- in the << operator
The former will complain with an error message and return 0 if the media
bus code is unknown, the latter will print the hex value.
bitsPerPixel() is used in CameraSensor::sensorInfo() only. We thus
complain already if a sensor has an unknown output format. We however
don't complain about unknown formats anywhere else, and there may thus
be places where we already handle them silently. I'm thinking in
particular about format propagation in the simple pipeline handler,
where we just get the format on the output of a subdevice and set it on
the input of the connected subdevice, without caring about the exact
format. We may also be use MEDIA_BUS_FMT_METADATA_FIXED without knowing
it, with the change here an attempt to call getFormat() on a subdev pad
that carries metadata will return in -EINVAL.
I would prefer keeping the current behaviour of selecting a reasonable
default in this patch series, and then add a stricter check on top if we
want to go that way.
> I am not much aware of simple pipeline handler format's passing - I'll
> take a look to answer the question - "Which default to pick"
>
> >> + 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.
>
> Ack
>
> >> 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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