[libcamera-devel] [PATCH 3/3] gstreamer: Provide colorimetry <> libcamera::ColorSpace mappings
Umang Jain
umang.jain at ideasonboard.com
Fri Jul 29 10:06:06 CEST 2022
Hi Laurent,
My anaylsis on sRGB mapping ...
On 7/27/22 06:47, Laurent Pinchart wrote:
> Hi Umang and Rishikesh,
>
> Thank you for the patch.
>
> On Sun, Jul 24, 2022 at 08:13:55PM +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
>> argument. Multiple colorimetry support shall be introduced in
>> subsequent commits.
>>
>> Signed-off-by: Rishikesh Donadkar <rishikeshdonadkar at gmail.com>
>> Signed-off-by: Umang Jain <umang.jain at ideasonboard.com>
>> ---
>> src/gstreamer/gstlibcamera-utils.cpp | 175 +++++++++++++++++++++++++++
>> 1 file changed, 175 insertions(+)
>>
>> diff --git a/src/gstreamer/gstlibcamera-utils.cpp b/src/gstreamer/gstlibcamera-utils.cpp
>> index c97c0d43..fb4f0e5c 100644
>> --- a/src/gstreamer/gstlibcamera-utils.cpp
>> +++ b/src/gstreamer/gstlibcamera-utils.cpp
>> @@ -45,6 +45,157 @@ 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;
> I would initialize the structure with all fields set to UNKNOWN here...
>
>> +
>> + 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;
>> + default:
>> + GST_WARNING("ColorSpace primaries not mapped in GstLibcameraSrc");
>> + colorimetry.primaries = GST_VIDEO_COLOR_PRIMARIES_UNKNOWN;
> ... and drop the default case. As ColorSpace::Primaries is an enum
> class, if you have cases for all the values, the compiler will warn only
> if one (or more) of the enum values isn't handled in explicit cases.
> This way you can avoid warnings, and have a guarantee that if the
> libcamera colorspaces are later extended, the compiler will remind that
> this function has to be updated. Same for the other components of the
> colorspace below.
>
>> + }
>> +
>> + 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;
>> + default:
>> + GST_WARNING("ColorSpace transfer function not mapped in GstLibcameraSrc");
>> + colorimetry.transfer = GST_VIDEO_TRANSFER_UNKNOWN;
>> + }
>> +
>> + switch (colorSpace.ycbcrEncoding) {
>> + 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:
>> + colorimetry.matrix = GST_VIDEO_COLOR_MATRIX_BT601;
>> + break;
>> + default:
>> + GST_WARNING("Colorspace YcbcrEncoding not mapped in GstLibcameraSrc");
>> + colorimetry.matrix = GST_VIDEO_COLOR_MATRIX_UNKNOWN;
> Should we map YcbcrEncoding::None to GST_VIDEO_COLOR_MATRIX_RGB ?
See below.
> Otherwise capturing RGB or raw bayer will produce a warning. Same for
> the Raw primaries, it seems that the best mapping would be
> GST_VIDEO_COLOR_PRIMARIES_UNKNOWN (unless I'm missing something), but I
> don't think we should warn in that case.
>
>> + }
>> +
>> + 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;
>> + default:
>> + GST_WARNING("Colorspace range not mapped in GstLibcameraSrc");
>> + colorimetry.range = GST_VIDEO_COLOR_RANGE_UNKNOWN;
>> + }
>> +
>> + return colorimetry;
>> +}
>> +
>> +static std::optional<ColorSpace>
>> +colorspace_from_colorimetry(GstVideoColorimetry *colorimetry)
> I'd pass a const reference instead of a pointer, as there's no use case
> for a null colorimetry.
>
>> +{
>> + std::optional<ColorSpace> colorspace = ColorSpace::Default;
> No need for std::optional here or in the return type.
>
>> +
>> + 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:
>> + colorspace->primaries = ColorSpace::Primaries::Default;
>> + break;
>> + default:
>> + GST_WARNING("Unknown primaries in colorimetry %d", colorimetry->primaries);
>> + }
>> +
>> + switch (colorimetry->transfer) {
>> + /* Tranfer 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;
>> + case GST_VIDEO_TRANSFER_UNKNOWN:
>> + colorspace->transferFunction = ColorSpace::TransferFunction::Default;
>> + break;
>> + default:
>> + GST_WARNING("Unknown colorimetry transfer %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:
>> + 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;
>> + case GST_VIDEO_COLOR_MATRIX_RGB:
> Shouldn't this map to YcbcrEncoding::None ?
YcbcrEncoding for sRGB as per Kernel is V4L2_YCBCR_ENC_SYCC which is
deprecated so V4L2_YCBCR_ENC_601 is used instead [1]
The same has been applied *already* in libcamera codebase:
const ColorSpace ColorSpace::Srgb = {
Primaries::Rec709,
TransferFunction::Srgb,
YcbcrEncoding::Rec601,
Range::Limited
};
So we shouldn't map GST_VIDEO_COLOR_MATRIX_RGB to YcbcrEncoding::None
but to Rec601 instead.
Now two question arises for reverse mapping it i.e. what should:
a) YcbcrEncding::None map to
b) YcbcrEncding::Rec601 map to.
For b) we have two contenders:
GST_VIDEO_COLOR_MATRIX_BT601
GST_VIDEO_COLOR_MATRIX_RGB
For a) I think GST_VIDEO_COLOR_MATRIX_RGB would be better ?
[1]
https://git.linuxtv.org/media_tree.git/tree/include/uapi/linux/videodev2.h#n344
>
>> + case GST_VIDEO_COLOR_MATRIX_UNKNOWN:
>> + colorspace->ycbcrEncoding = ColorSpace::YcbcrEncoding::Default;
>> + break;
>> + default:
>> + GST_WARNING("Unknown 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;
>> + case GST_VIDEO_COLOR_RANGE_UNKNOWN:
>> + colorspace->range = ColorSpace::Range::Default;
>> + break;
>> + default:
>> + GST_WARNING("Unknown range in colorimetry %d", colorimetry->range);
>> + }
>> +
>> + return colorspace;
>> +}
>> +
>> static GstVideoFormat
>> pixel_format_to_gst_format(const PixelFormat &format)
>> {
>> @@ -139,6 +290,17 @@ 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 != nullptr)
> if (colorimetry_str)
>
>> + gst_structure_set(s, "colorimetry", G_TYPE_STRING, colorimetry_str, nullptr);
>> + else
>> + g_warning("libcamera::ColorSpace found but GstVideoColorimetry unknown");
>> + }
>> +
>> gst_caps_append_structure(caps, s);
>>
>> return caps;
>> @@ -222,6 +384,19 @@ 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".
>
>> + std::optional<ColorSpace> colorSpace = colorspace_from_colorimetry(&colorimetry);
>> + stream_cfg.colorSpace = colorSpace;
> stream_cfg.colorSpace = colorspace_from_colorimetry(&colorimetry);
>
>> + } else {
>> + g_print("Invalid colorimetry %s", colorimetry_caps);
>> + }
>> + }
>> }
>>
>> #if !GST_CHECK_VERSION(1, 17, 1)
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