[libcamera-devel] [PATCH v1 1/2] gstreamer: Provide colorimetry <> ColorSpace mappings

[Laurent Pinchart]

Hi Rishikesh,

Thank you for the patch.

On Sun, Aug 07, 2022 at 05:42:32PM +0530, Rishikesh Donadkar via libcamera-devel wrote:
> 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.

Your SoB line is missing.

> ---
>  src/gstreamer/gstlibcamera-utils.cpp | 158 +++++++++++++++++++++++++++
>  1 file changed, 158 insertions(+)
> 
> diff --git a/src/gstreamer/gstlibcamera-utils.cpp b/src/gstreamer/gstlibcamera-utils.cpp
> index c97c0d43..24d8d035 100644
> --- a/src/gstreamer/gstlibcamera-utils.cpp
> +++ b/src/gstreamer/gstlibcamera-utils.cpp
> @@ -45,6 +45,152 @@ 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::Raw:
> +		colorimetry.primaries = GST_VIDEO_COLOR_PRIMARIES_UNKNOWN;
> +		break;
> +	case ColorSpace::Primaries::Smpte170m:
> +		colorimetry.primaries = GST_VIDEO_COLOR_PRIMARIES_SMPTE170M;
> +		break;
> +	case ColorSpace::Primaries::Rec709:
> +		colorimetry.primaries = GST_VIDEO_COLOR_PRIMARIES_BT709;
> +		break;
> +	case ColorSpace::Primaries::Rec2020:
> +		colorimetry.primaries = GST_VIDEO_COLOR_PRIMARIES_BT2020;
> +		break;
> +	}
> +
> +	switch (colorSpace.transferFunction) {
> +	case ColorSpace::TransferFunction::Linear:
> +		colorimetry.transfer = GST_VIDEO_TRANSFER_GAMMA10;
> +		break;
> +	case ColorSpace::TransferFunction::Srgb:
> +		colorimetry.transfer = GST_VIDEO_TRANSFER_SRGB;
> +		break;
> +	case ColorSpace::TransferFunction::Rec709:
> +		colorimetry.transfer = GST_VIDEO_TRANSFER_BT709;
> +		break;
> +	}
> +
> +	switch (colorSpace.ycbcrEncoding) {
> +	case ColorSpace::YcbcrEncoding::None:
> +		colorimetry.matrix = GST_VIDEO_COLOR_MATRIX_RGB;
> +		break;
> +	case ColorSpace::YcbcrEncoding::Rec601:
> +		colorimetry.matrix = GST_VIDEO_COLOR_MATRIX_BT601;
> +		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;
> +	}
> +
> +	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_UNKNOWN:
> +		/* Unknown primaries map to raw colorspace in gstreamer */

s/gstreamer/GStreamer./

> +		return ColorSpace::Raw;
> +	case GST_VIDEO_COLOR_PRIMARIES_SMPTE170M:
> +		colorspace.primaries = ColorSpace::Primaries::Smpte170m;
> +		break;
> +	case GST_VIDEO_COLOR_PRIMARIES_BT709:
> +		colorspace.primaries = ColorSpace::Primaries::Rec709;
> +		break;
> +	case GST_VIDEO_COLOR_PRIMARIES_BT2020:
> +		colorspace.primaries = ColorSpace::Primaries::Rec2020;
> +		break;
> +	default:
> +		GST_WARNING("Colorimetry primaries %d not mapped in gstlibcamera",
> +			    colorimetry.primaries);
> +		return ColorSpace::Raw;
> +	}
> +
> +	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_SRGB:
> +		colorspace.transferFunction = ColorSpace::TransferFunction::Srgb;
> +		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;
> +	default:
> +		GST_WARNING("Colorimetry transfer function %d not mapped in gstlibcamera",
> +			    colorimetry.transfer);
> +		return ColorSpace::Raw;
> +	}
> +
> +	switch (colorimetry.matrix) {
> +	case GST_VIDEO_COLOR_MATRIX_RGB:
> +		colorspace.ycbcrEncoding = ColorSpace::YcbcrEncoding::None;
> +		break;
> +	/* FCC is about the same as BT601 with less digit */

s/digit/digits./

> +	case GST_VIDEO_COLOR_MATRIX_FCC:
> +	case GST_VIDEO_COLOR_MATRIX_BT601:
> +		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:
> +		GST_WARNING("Colorimetry matrix %d not mapped in gstlibcamera",
> +			    colorimetry.matrix);
> +		return ColorSpace::Raw;
> +	}
> +
> +	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:
> +		GST_WARNING("Colorimetry range %d not mapped in gstlibcamera",
> +			    colorimetry.range);
> +		return ColorSpace::Raw;
> +	}
> +
> +	return colorspace;
> +}
> +
>  static GstVideoFormat
>  pixel_format_to_gst_format(const PixelFormat &format)
>  {
> @@ -139,6 +285,18 @@ 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());
> +	}
> +

This looks fine, but I think you're missing a part of the patch, as
colorspace_from_colorimetry() is not used. One option is to move the
function to patch 2/2, otherwise compiling this patch alone will
generate a compilation warning.

If you do that, the commit message should also be updated, to reflect
that this patch only handles the colorimetry in the libcamera to
GStreamer direction.

>  	gst_caps_append_structure(caps, s);
>  
>  	return caps;

-- 
Regards,

Laurent Pinchart