v4l2: Fix 4K colorimetry

Since 1.6, the transfer function for BT2020 has been changed from BT709
to BT2020_12. It's the same function, but with more precision. As a side
effect, the V4L2 colorpsace didn't match GStreamer colorspace. When
GStreamer ended up making a guess, it would not match anything supported
by V4L2 anymore. This this by using BT2020_12 for BT2020 colorspace and
BT2020 transfer function in replacement of BT709 whenever a 4K
resolution is detected.

diff --git a/sys/v4l2/gstv4l2object.c b/sys/v4l2/gstv4l2object.c
index 6f7d8dd..96986bf 100644 (file)
--- a/sys/v4l2/gstv4l2object.c
+++ b/sys/v4l2/gstv4l2object.c
@@ -1924,7 +1924,7 @@ gst_v4l2_object_get_colorspace (struct v4l2_format *fmt,
     case V4L2_COLORSPACE_BT2020:
       cinfo->range = GST_VIDEO_COLOR_RANGE_16_235;
       cinfo->matrix = GST_VIDEO_COLOR_MATRIX_BT2020;
-      cinfo->transfer = GST_VIDEO_TRANSFER_BT709;
+      cinfo->transfer = GST_VIDEO_TRANSFER_BT2020_12;
       cinfo->primaries = GST_VIDEO_COLOR_PRIMARIES_BT2020;
       break;
     case V4L2_COLORSPACE_SMPTE240M:
@@ -2026,7 +2026,10 @@ gst_v4l2_object_get_colorspace (struct v4l2_format *fmt,
 
   switch (transfer) {
     case V4L2_XFER_FUNC_709:
-      cinfo->transfer = GST_VIDEO_TRANSFER_BT709;
+      if (fmt->fmt.pix.height > 2160)
+        cinfo->transfer = GST_VIDEO_TRANSFER_BT2020_12;
+      else
+        cinfo->transfer = GST_VIDEO_TRANSFER_BT709;
       break;
     case V4L2_XFER_FUNC_SRGB:
       cinfo->transfer = GST_VIDEO_TRANSFER_SRGB;