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-rw-r--r--Documentation/media/uapi/v4l/pixfmt-007.rst13
1 files changed, 9 insertions, 4 deletions
diff --git a/Documentation/media/uapi/v4l/pixfmt-007.rst b/Documentation/media/uapi/v4l/pixfmt-007.rst
index 95a23a28c595..0c30ee2577d3 100644
--- a/Documentation/media/uapi/v4l/pixfmt-007.rst
+++ b/Documentation/media/uapi/v4l/pixfmt-007.rst
@@ -174,7 +174,7 @@ this colorspace:
The xvYCC 709 encoding (``V4L2_YCBCR_ENC_XV709``, :ref:`xvycc`) is
similar to the Rec. 709 encoding, but it allows for R', G' and B' values
that are outside the range [0…1]. The resulting Y', Cb and Cr values are
-scaled and offset:
+scaled and offset according to the limited range formula:
.. math::
@@ -187,7 +187,7 @@ scaled and offset:
The xvYCC 601 encoding (``V4L2_YCBCR_ENC_XV601``, :ref:`xvycc`) is
similar to the BT.601 encoding, but it allows for R', G' and B' values
that are outside the range [0…1]. The resulting Y', Cb and Cr values are
-scaled and offset:
+scaled and offset according to the limited range formula:
.. math::
@@ -198,9 +198,14 @@ scaled and offset:
Cr = \frac{224}{256} * (0.5R' - 0.4187G' - 0.0813B')
Y' is clamped to the range [0…1] and Cb and Cr are clamped to the range
-[-0.5…0.5]. The non-standard xvYCC 709 or xvYCC 601 encodings can be
+[-0.5…0.5] and quantized without further scaling or offsets.
+The non-standard xvYCC 709 or xvYCC 601 encodings can be
used by selecting ``V4L2_YCBCR_ENC_XV709`` or ``V4L2_YCBCR_ENC_XV601``.
-The xvYCC encodings always use full range quantization.
+As seen by the xvYCC formulas these encodings always use limited range quantization,
+there is no full range variant. The whole point of these extended gamut encodings
+is that values outside the limited range are still valid, although they
+map to R', G' and B' values outside the [0…1] range and are therefore outside
+the Rec. 709 colorspace gamut.
.. _col-srgb: