[libcamera-devel] [PATCH v6 4/7] libcamera: Support passing ColorSpaces to V4L2 video devices

[Umang Jain]

Hi David,

On 11/18/21 8:49 PM, David Plowman wrote:
> The ColorSpace from the StreamConfiguration is now handled
> appropriately in the V4L2VideoDevice.
>
> Signed-off-by: David Plowman <david.plowman at raspberrypi.com>
> ---
>   include/libcamera/internal/v4l2_videodevice.h |  2 +
>   src/libcamera/v4l2_videodevice.cpp            | 53 +++++++++++++++++--
>   2 files changed, 51 insertions(+), 4 deletions(-)
>
> diff --git a/include/libcamera/internal/v4l2_videodevice.h b/include/libcamera/internal/v4l2_videodevice.h
> index a1c458e4..00bc50e7 100644
> --- a/include/libcamera/internal/v4l2_videodevice.h
> +++ b/include/libcamera/internal/v4l2_videodevice.h
> @@ -20,6 +20,7 @@
>   #include <libcamera/base/log.h>
>   #include <libcamera/base/signal.h>
>   
> +#include <libcamera/color_space.h>
>   #include <libcamera/framebuffer.h>
>   #include <libcamera/geometry.h>
>   #include <libcamera/pixel_format.h>
> @@ -167,6 +168,7 @@ public:
>   
>   	V4L2PixelFormat fourcc;
>   	Size size;
> +	std::optional<ColorSpace> colorSpace;
>   
>   	std::array<Plane, 3> planes;
>   	unsigned int planesCount = 0;
> diff --git a/src/libcamera/v4l2_videodevice.cpp b/src/libcamera/v4l2_videodevice.cpp
> index 4f04212d..e03ff8b5 100644
> --- a/src/libcamera/v4l2_videodevice.cpp
> +++ b/src/libcamera/v4l2_videodevice.cpp
> @@ -370,17 +370,27 @@ bool V4L2BufferCache::Entry::operator==(const FrameBuffer &buffer) const
>    * \brief The plane line stride (in bytes)
>    */
>   
> +/**
> + * \var V4L2DeviceFormat::fourcc
> + * \brief The fourcc code describing the pixel encoding scheme
> + *
> + * The fourcc code, as defined by the V4L2 API with the V4L2_PIX_FMT_* macros,
> + * that identifies the image format pixel encoding scheme.
> + */
> +
>   /**
>    * \var V4L2DeviceFormat::size
>    * \brief The image size in pixels
>    */
>   
>   /**
> - * \var V4L2DeviceFormat::fourcc
> - * \brief The fourcc code describing the pixel encoding scheme
> + * \var V4L2DeviceFormat::colorSpace
> + * \brief The color space of the pixels
>    *
> - * The fourcc code, as defined by the V4L2 API with the V4L2_PIX_FMT_* macros,
> - * that identifies the image format pixel encoding scheme.
> + * The color space of the image. When setting the format this may be
> + * unset, in which case the driver gets to use its default color space.
> + * After being set, this value should contain the color space that the
> + * was actually used.
>    */
>   
>   /**
> @@ -879,6 +889,10 @@ int V4L2VideoDevice::getFormatMultiplane(V4L2DeviceFormat *format)
>   	format->fourcc = V4L2PixelFormat(pix->pixelformat);
>   	format->planesCount = pix->num_planes;
>   
> +	format->colorSpace = toColorSpace(*pix);
> +	if (!format->colorSpace)
> +		LOG(V4L2, Error) << "Retrieved unrecognised color space";


You have marked this as an Error, should we be return here too?

> +
>   	for (unsigned int i = 0; i < format->planesCount; ++i) {
>   		format->planes[i].bpl = pix->plane_fmt[i].bytesperline;
>   		format->planes[i].size = pix->plane_fmt[i].sizeimage;
> @@ -893,6 +907,9 @@ int V4L2VideoDevice::trySetFormatMultiplane(V4L2DeviceFormat *format, bool set)
>   	struct v4l2_pix_format_mplane *pix = &v4l2Format.fmt.pix_mp;
>   	int ret;
>   
> +	if (!format->colorSpace)
> +		LOG(V4L2, Warning) << "Setting undefined color space";
> +
>   	v4l2Format.type = bufferType_;
>   	pix->width = format->size.width;
>   	pix->height = format->size.height;
> @@ -900,6 +917,12 @@ int V4L2VideoDevice::trySetFormatMultiplane(V4L2DeviceFormat *format, bool set)
>   	pix->num_planes = format->planesCount;
>   	pix->field = V4L2_FIELD_NONE;
>   
> +	ret = fromColorSpace(format->colorSpace, *pix);
> +	if (ret < 0)
> +		LOG(V4L2, Warning)
> +			<< "Setting color space unrecognised by V4L2: "
> +			<< ColorSpace::toString(format->colorSpace);
> +
>   	ASSERT(pix->num_planes <= std::size(pix->plane_fmt));
>   
>   	for (unsigned int i = 0; i < pix->num_planes; ++i) {
> @@ -928,6 +951,10 @@ int V4L2VideoDevice::trySetFormatMultiplane(V4L2DeviceFormat *format, bool set)
>   		format->planes[i].size = pix->plane_fmt[i].sizeimage;
>   	}
>   
> +	format->colorSpace = toColorSpace(*pix);
> +	if (!format->colorSpace)
> +		LOG(V4L2, Warning) << "Unrecognised color space has been set";
> +
>   	return 0;
>   }
>   
> @@ -951,6 +978,10 @@ int V4L2VideoDevice::getFormatSingleplane(V4L2DeviceFormat *format)
>   	format->planes[0].bpl = pix->bytesperline;
>   	format->planes[0].size = pix->sizeimage;
>   
> +	format->colorSpace = toColorSpace(*pix);
> +	if (!format->colorSpace)
> +		LOG(V4L2, Error) << "Retrieved unrecognised color space";
> +
>   	return 0;
>   }
>   
> @@ -960,12 +991,22 @@ int V4L2VideoDevice::trySetFormatSingleplane(V4L2DeviceFormat *format, bool set)
>   	struct v4l2_pix_format *pix = &v4l2Format.fmt.pix;
>   	int ret;
>   
> +	if (!format->colorSpace)
> +		LOG(V4L2, Error) << "Trying to set unrecognised color space";
> +
>   	v4l2Format.type = bufferType_;
>   	pix->width = format->size.width;
>   	pix->height = format->size.height;
>   	pix->pixelformat = format->fourcc;
>   	pix->bytesperline = format->planes[0].bpl;
>   	pix->field = V4L2_FIELD_NONE;
> +
> +	ret = fromColorSpace(format->colorSpace, *pix);
> +	if (ret < 0)
> +		LOG(V4L2, Warning)
> +			<< "Set color space unrecognised by V4L2: "
> +			<< ColorSpace::toString(format->colorSpace);
> +
>   	ret = ioctl(set ? VIDIOC_S_FMT : VIDIOC_TRY_FMT, &v4l2Format);
>   	if (ret) {
>   		LOG(V4L2, Error)
> @@ -985,6 +1026,10 @@ int V4L2VideoDevice::trySetFormatSingleplane(V4L2DeviceFormat *format, bool set)
>   	format->planes[0].bpl = pix->bytesperline;
>   	format->planes[0].size = pix->sizeimage;
>   
> +	format->colorSpace = toColorSpace(*pix);
> +	if (!format->colorSpace)
> +		LOG(V4L2, Error) << "Undefined color space has been set";
> +


Similar concern here.

I am finding the Error/Warning strings to be a bit confusing. 
Set/Setting "undefined/unrecognised" color space = What does that mean 
actually? Is it about unsetting the color space so that the driver can 
use and set it's default one?

>   	return 0;
>   }
>