GES 1.16.1 -- Jpeg images may be rendered without respecting colorimetry

[David Ing]

I am using GES to embed a jpeg file into a timeline.  When I view the
output video, the color is slightly off.  I believe the problem is related
to colorimetry.

I attached the graph (as pipeline_graph.svg).

When I analyze the JPEG file using ffprobe, I can see some properties
related to colorimetry.

ffprobe -show_streams file.jpg

color_range=pc
color_space=bt470bg
color_transfer=unknown
color_primaries=unknown
chroma_location=center

I can see that jpegdec has the following coming from its source pad ...

video/x-raw:

...

chroma-site: mpeg2

colorimetry: 1:4:0:0

...


... where the colorimetry information is basically:

GST_VIDEO_COLOR_RANGE_0_255
GST_VIDEO_COLOR_MATRIX_BT601  (probably equivalent to bt470bg)
GST_VIDEO_TRANSFER_UNKNOWN
GST_VIDEO_COLOR_PRIMARIES_UNKNOWN


I can see in the graph that these caps are exposed all the way through
GstUriDecodeBin (within the GESVideoTrack of the GESTimeline).

But the GstUriDecodeBin passes its output to a GstVideoScale, and the
colorimetry data gets removed from the caps at that point.

My questions are:

   1. Without colorimetry information in the caps, there would be no way
   for subsequent elements to perform the correct color transformation, right?
   2. Is this a bug in GES?
   3. Can anyone provide hints about fixing this bugin GES?  (If it is a
   bug.)
   4. Can anyone recommend a simple workaround?
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