[libcamera-devel] [PATCH v2] gstreamer: Provide colorimetry <> ColorSpace mappings
Laurent Pinchart
laurent.pinchart at ideasonboard.com
Mon Aug 1 14:42:05 CEST 2022
Hi Umang,
On Mon, Aug 01, 2022 at 06:01:40PM +0530, Umang Jain wrote:
> On 8/1/22 01:14, Laurent Pinchart wrote:
> > Hi Umang and Rishikesh,
> >
> > (Cc'ing David)
> >
> > Thank you for the patch.
> >
> > On Fri, Jul 29, 2022 at 04:08:46PM +0530, Umang Jain via libcamera-devel wrote:
> >> From: Rishikesh Donadkar <rishikeshdonadkar at gmail.com>
> >>
> >> Provide colorimetry <=> libcamera::ColorSpace mappings via:
> >> - GstVideoColorimetry colorimetry_from_colorspace(colorspace);
> >> - ColorSpace colorspace_from_colorimetry(colorimetry);
> >>
> >> Read the colorimetry field from caps into the stream configuration.
> >> After stream validation, the sensor supported colorimetry will
> >> be retrieved and the caps will be updated accordingly.
> >>
> >> Colorimetry support for gstlibcamerasrc currently undertakes only one
> >
> > s/gstlibcamerasrc/libcamerasrc/ (or gstlibcamera if you meant the
> > library, not the element name)
> >
> >> argument. Multiple colorimetry support shall be introduced in
> >> subsequent commits.
> >
> > I'm probably missing something here, what do you mean by multiple
> > colorimetry support ?
> >
> >> Signed-off-by: Rishikesh Donadkar <rishikeshdonadkar at gmail.com>
> >> Signed-off-by: Umang Jain <umang.jain at ideasonboard.com>
> >> ---
> >>
> >> Changes in v2:
> >> - Drop "Default" Colorspace
> >> - Improve function signature of colorimetry_from_colorspace() and
> >> colorspace_from_colorimetry()
> >> - Map GST_VIDEO_COLOR_MATRIX_RGB to Colorspace::YcbcrEncoding::Rec601
> >> (comes from the kernel)
> >> - Map GST_VIDEO_COLOR_PRIMARIES_UNKNOWN to Raw colorspace
> >> - Map ColorSpace::YcbcrEncoding::Rec601 to GST_VIDEO_COLOR_MATRIX_RGB
> >> if colorspace is "sRGB". GST_VIDEO_COLOR_MATRIX_BT601 for all other
> >> cases
> >> - Minor nits regarding error reporting strings.
> >> ---
> >> src/gstreamer/gstlibcamera-utils.cpp | 164 +++++++++++++++++++++++++++
> >> 1 file changed, 164 insertions(+)
> >>
> >> diff --git a/src/gstreamer/gstlibcamera-utils.cpp b/src/gstreamer/gstlibcamera-utils.cpp
> >> index c97c0d43..e4ff1269 100644
> >> --- a/src/gstreamer/gstlibcamera-utils.cpp
> >> +++ b/src/gstreamer/gstlibcamera-utils.cpp
> >> @@ -45,6 +45,146 @@ static struct {
> >> /* \todo NV42 is used in libcamera but is not mapped in GStreamer yet. */
> >> };
> >>
> >> +static GstVideoColorimetry
> >> +colorimetry_from_colorspace(const ColorSpace &colorSpace)
> >> +{
> >> + GstVideoColorimetry colorimetry;
> >> +
> >> + switch (colorSpace.primaries) {
> >> + case ColorSpace::Primaries::Rec709:
> >> + colorimetry.primaries = GST_VIDEO_COLOR_PRIMARIES_BT709;
> >> + break;
> >> + case ColorSpace::Primaries::Rec2020:
> >> + colorimetry.primaries = GST_VIDEO_COLOR_PRIMARIES_BT2020;
> >> + break;
> >> + case ColorSpace::Primaries::Smpte170m:
> >> + colorimetry.primaries = GST_VIDEO_COLOR_PRIMARIES_SMPTE170M;
> >> + break;
> >> + case ColorSpace::Primaries::Raw:
> >> + colorimetry.primaries = GST_VIDEO_COLOR_PRIMARIES_UNKNOWN;
> >> + break;
> >> + }
> >
> > I'd sort the cases with the order of the enum in color_space.h (below
> > too). That's very minor.
>
> Ack.
>
> >> +
> >> + switch (colorSpace.transferFunction) {
> >> + case ColorSpace::TransferFunction::Rec709:
> >> + colorimetry.transfer = GST_VIDEO_TRANSFER_BT709;
> >> + break;
> >> + case ColorSpace::TransferFunction::Srgb:
> >> + colorimetry.transfer = GST_VIDEO_TRANSFER_SRGB;
> >> + break;
> >> + case ColorSpace::TransferFunction::Linear:
> >> + colorimetry.transfer = GST_VIDEO_TRANSFER_GAMMA10;
> >> + break;
> >> + }
> >> +
> >> + switch (colorSpace.ycbcrEncoding) {
> >> + case ColorSpace::YcbcrEncoding::None:
> >> + colorimetry.matrix = GST_VIDEO_COLOR_MATRIX_RGB;
> >> + break;
> >> + case ColorSpace::YcbcrEncoding::Rec709:
> >> + colorimetry.matrix = GST_VIDEO_COLOR_MATRIX_BT709;
> >> + break;
> >> + case ColorSpace::YcbcrEncoding::Rec2020:
> >> + colorimetry.matrix = GST_VIDEO_COLOR_MATRIX_BT2020;
> >> + break;
> >> + case ColorSpace::YcbcrEncoding::Rec601:
> >> + if (colorSpace == ColorSpace::Srgb)
> >> + colorimetry.matrix = GST_VIDEO_COLOR_MATRIX_RGB;
> >
> > I don't think this one is right. GST_VIDEO_COLOR_MATRIX_RGB is the
> > identity matrix, which means no encoding to YCbCr, and
> > ColorSpace::YcbcrEncoding::Rec601 clearly defines an encoding.
> >
> > I think the problem is caused by our definition of ColorSpace::Srgb:
> >
> > const ColorSpace ColorSpace::Srgb = {
> > Primaries::Rec709,
> > TransferFunction::Srgb,
> > YcbcrEncoding::Rec601,
> > Range::Limited
> > };
> >
> > I propose modifying it to
> >
> > const ColorSpace ColorSpace::Srgb = {
> > Primaries::Rec709,
> > TransferFunction::Srgb,
> > YcbcrEncoding::None,
> > Range::Full
> > };
>
> ack!
>
> My question which I think I brought up in v1 itself now (you can choose
> to reply anywhere) is, do we need a preset to represent YUV-encoded RGB
> and what would we call it? ColorSpace::sYCC ?
I think it would make sense, the only thing is that I don't know how
widely it is used to make it worth a color space preset. Regardless of
whether or not we create a preset, the V4L2Device class should be fixed
if needed to perform the conversion to/from V4L2 correctly.
> > and adapting the rest of libcamera accordingly.
> >
> > David, this will affect Raspberry Pi, so I'd appreciate your opinion.
>
> Patiently waiting ;-)
>
> >> + else
> >> + colorimetry.matrix = GST_VIDEO_COLOR_MATRIX_BT601;
> >> + break;
> >> + }
> >> +
> >> + switch (colorSpace.range) {
> >> + case ColorSpace::Range::Full:
> >> + colorimetry.range = GST_VIDEO_COLOR_RANGE_0_255;
> >> + break;
> >> + case ColorSpace::Range::Limited:
> >> + colorimetry.range = GST_VIDEO_COLOR_RANGE_16_235;
> >> + break;
> >> + }
> >> +
> >> + return colorimetry;
> >> +}
> >> +
> >> +static ColorSpace
> >> +colorspace_from_colorimetry(const GstVideoColorimetry &colorimetry)
> >> +{
> >> + ColorSpace colorspace = ColorSpace::Raw;
> >> +
> >> + switch (colorimetry.primaries) {
> >> + case GST_VIDEO_COLOR_PRIMARIES_BT709:
> >> + colorspace.primaries = ColorSpace::Primaries::Rec709;
> >> + break;
> >> + case GST_VIDEO_COLOR_PRIMARIES_BT2020:
> >> + colorspace.primaries = ColorSpace::Primaries::Rec2020;
> >> + break;
> >> + case GST_VIDEO_COLOR_PRIMARIES_SMPTE170M:
> >> + colorspace.primaries = ColorSpace::Primaries::Smpte170m;
> >> + break;
> >> + case GST_VIDEO_COLOR_PRIMARIES_UNKNOWN:
> >> + /* Unknown primaries map to raw colorspace in gstreamer */
> >> + return colorspace;
> >
> > I would
> >
> > return ColorSpace::Raw;
> >
> > here to make it more explicit.
>
> ack
>
> >> + default:
> >> + g_error("Unsupported colorimetry primaries: %d", colorimetry.primaries);
> >
> > g_error() seems very harsh, do we really need to abort() if the user
> > asks for unsupported primaries (or other colorimetry fields below) ?
>
> I agree it's harsh - initially I kept as 'warning' but then it was
> advised that 'warnings' always come with mitigation steps.
>
> I guess the only mitigation technique here is, making sure mappings exists!
GStreamer defines more primaries than libcamera, so it seems to me that
a user could trigger a g_error() simply by specifying an unsupported
primary on the command line, which isn't great. Depending on what
GStreamer expect in that case, we should either fall back to a support
primary, or return an error that can be handled by GStreamer to fail
caps negotiation instead of aborting.
> > This is probably a question for Nicolas.
> >
> >> + }
> >> +
> >> + switch (colorimetry.transfer) {
> >> + /* Transfer function mappings inspired from v4l2src plugin */
> >> + case GST_VIDEO_TRANSFER_GAMMA18:
> >> + case GST_VIDEO_TRANSFER_GAMMA20:
> >> + case GST_VIDEO_TRANSFER_GAMMA22:
> >> + case GST_VIDEO_TRANSFER_GAMMA28:
> >> + GST_WARNING("GAMMA 18, 20, 22, 28 transfer functions not supported");
> >> + /* fallthrough */
> >> + case GST_VIDEO_TRANSFER_GAMMA10:
> >> + colorspace.transferFunction = ColorSpace::TransferFunction::Linear;
> >> + break;
> >> + case GST_VIDEO_TRANSFER_BT601:
> >> + case GST_VIDEO_TRANSFER_BT2020_12:
> >> + case GST_VIDEO_TRANSFER_BT2020_10:
> >> + case GST_VIDEO_TRANSFER_BT709:
> >> + colorspace.transferFunction = ColorSpace::TransferFunction::Rec709;
> >> + break;
> >> + case GST_VIDEO_TRANSFER_SRGB:
> >> + colorspace.transferFunction = ColorSpace::TransferFunction::Srgb;
> >> + break;
> >> + default:
> >> + g_error("Unsupported colorimetry transfer function: %d", colorimetry.transfer);
> >> + }
> >> +
> >> + switch (colorimetry.matrix) {
> >> + /* FCC is about the same as BT601 with less digit */
> >> + case GST_VIDEO_COLOR_MATRIX_FCC:
> >> + case GST_VIDEO_COLOR_MATRIX_BT601:
> >> + /* v4l2_ycbcr_encoding of sRGB is ENC_601 in the kernel */
> >
> > That's right, but I don't think we need to be concerned by that here.
> > GST_VIDEO_COLOR_MATRIX_RGB should be mapped to
> > ColorSpace::YcbcrEncoding::None, and we should handle the V4L2 sRGB YUV
> > encoding internally in libcamera.
>
> replied to the latter part, in detail, in v1
>
> >> + case GST_VIDEO_COLOR_MATRIX_RGB:
> >> + colorspace.ycbcrEncoding = ColorSpace::YcbcrEncoding::Rec601;
> >> + break;
> >> + case GST_VIDEO_COLOR_MATRIX_BT709:
> >> + colorspace.ycbcrEncoding = ColorSpace::YcbcrEncoding::Rec709;
> >> + break;
> >> + case GST_VIDEO_COLOR_MATRIX_BT2020:
> >> + colorspace.ycbcrEncoding = ColorSpace::YcbcrEncoding::Rec2020;
> >> + break;
> >> + default:
> >> + g_error("Unsupported colorimetry matrix: %d", colorimetry.matrix);
> >> + }
> >> +
> >> + switch (colorimetry.range) {
> >> + case GST_VIDEO_COLOR_RANGE_0_255:
> >> + colorspace.range = ColorSpace::Range::Full;
> >> + break;
> >> + case GST_VIDEO_COLOR_RANGE_16_235:
> >> + colorspace.range = ColorSpace::Range::Limited;
> >> + break;
> >> + default:
> >> + g_error("Unsupported colorimetry range %d", colorimetry.range);
> >> + }
> >> +
> >> + return colorspace;
> >> +}
> >> +
> >> static GstVideoFormat
> >> pixel_format_to_gst_format(const PixelFormat &format)
> >> {
> >> @@ -139,6 +279,18 @@ gst_libcamera_stream_configuration_to_caps(const StreamConfiguration &stream_cfg
> >> "width", G_TYPE_INT, stream_cfg.size.width,
> >> "height", G_TYPE_INT, stream_cfg.size.height,
> >> nullptr);
> >> +
> >> + if (stream_cfg.colorSpace) {
> >> + GstVideoColorimetry colorimetry = colorimetry_from_colorspace(stream_cfg.colorSpace.value());
> >> + gchar *colorimetry_str = gst_video_colorimetry_to_string(&colorimetry);
> >> +
> >> + if (colorimetry_str)
> >> + gst_structure_set(s, "colorimetry", G_TYPE_STRING, colorimetry_str, nullptr);
> >> + else
> >> + g_error("Got invalid colorimetry from ColorSpace: %s",
> >> + ColorSpace::toString(stream_cfg.colorSpace).c_str());
> >
> > Same question as above about g_error(). As far as I understand,
> > gst_video_colorimetry_to_string() will return null either if it can't
> > alocate memory for the string (in which case we're screwed anyway, so
> > g_error() is fine) or if colorimetry is all UNKNOWN. The latter should
> > never happen given the implementation of colorimetry_from_colorspace(),
> > so I suppose it's fine ?
>
> Yes, I think it's fine
>
> >> + }
> >> +
> >> gst_caps_append_structure(caps, s);
> >>
> >> return caps;
> >> @@ -222,6 +374,18 @@ gst_libcamera_configure_stream_from_caps(StreamConfiguration &stream_cfg,
> >> gst_structure_get_int(s, "height", &height);
> >> stream_cfg.size.width = width;
> >> stream_cfg.size.height = height;
> >> +
> >> + /* Configure colorimetry */
> >> + if (gst_structure_has_field(s, "colorimetry")) {
> >> + const gchar *colorimetry_caps = gst_structure_get_string(s, "colorimetry");
> >> + GstVideoColorimetry colorimetry;
> >> +
> >> + if(gst_video_colorimetry_from_string(&colorimetry, colorimetry_caps)) {
> >
> > Missing space after "if".
> >
> >> + stream_cfg.colorSpace = colorspace_from_colorimetry(colorimetry);
> >> + } else {
> >> + g_critical("Invalid colorimetry %s", colorimetry_caps);
> >> + }
> >> + }
> >> }
> >>
> >> #if !GST_CHECK_VERSION(1, 17, 1)
--
Regards,
Laurent Pinchart
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