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authorHans Verkuil <hverkuil@xs4all.nl>2017-02-10 07:18:36 -0200
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2017-02-23 17:44:37 +0100
commit7b071234537686546c5f05fdcb40a33ade2f6b04 (patch)
tree02333fe8c7bf1713b09499a8ee47f583d9e2b6ff
parent8629aed2387cd22d1bde76e798034c3ea31018f7 (diff)
videodev2.h: go back to limited range Y'CbCr for SRGB and, ADOBERGB
commit 35879ee4769099905fa3bda0b21e73d434e2df6a upstream. This reverts 'commit 7e0739cd9c40 ("[media] videodev2.h: fix sYCC/AdobeYCC default quantization range"). The problem is that many drivers can convert R'G'B' content (often from sensors) to Y'CbCr, but they all produce limited range Y'CbCr. To stay backwards compatible the default quantization range for sRGB and AdobeRGB Y'CbCr encoding should be limited range, not full range, even though the corresponding standards specify full range. Update the V4L2_MAP_QUANTIZATION_DEFAULT define accordingly and also update the documentation. Fixes: 7e0739cd9c40 ("[media] videodev2.h: fix sYCC/AdobeYCC default quantization range") Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com> Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--Documentation/media/uapi/v4l/pixfmt-007.rst23
-rw-r--r--include/uapi/linux/videodev2.h7
2 files changed, 20 insertions, 10 deletions
diff --git a/Documentation/media/uapi/v4l/pixfmt-007.rst b/Documentation/media/uapi/v4l/pixfmt-007.rst
index 44bb5a7059b3..95a23a28c595 100644
--- a/Documentation/media/uapi/v4l/pixfmt-007.rst
+++ b/Documentation/media/uapi/v4l/pixfmt-007.rst
@@ -211,7 +211,13 @@ Colorspace sRGB (V4L2_COLORSPACE_SRGB)
The :ref:`srgb` standard defines the colorspace used by most webcams
and computer graphics. The default transfer function is
``V4L2_XFER_FUNC_SRGB``. The default Y'CbCr encoding is
-``V4L2_YCBCR_ENC_601``. The default Y'CbCr quantization is full range.
+``V4L2_YCBCR_ENC_601``. The default Y'CbCr quantization is limited range.
+
+Note that the :ref:`sycc` standard specifies full range quantization,
+however all current capture hardware supported by the kernel convert
+R'G'B' to limited range Y'CbCr. So choosing full range as the default
+would break how applications interpret the quantization range.
+
The chromaticities of the primary colors and the white reference are:
@@ -276,7 +282,7 @@ the following ``V4L2_YCBCR_ENC_601`` encoding as defined by :ref:`sycc`:
Y' is clamped to the range [0…1] and Cb and Cr are clamped to the range
[-0.5…0.5]. This transform is identical to one defined in SMPTE
-170M/BT.601. The Y'CbCr quantization is full range.
+170M/BT.601. The Y'CbCr quantization is limited range.
.. _col-adobergb:
@@ -288,10 +294,15 @@ The :ref:`adobergb` standard defines the colorspace used by computer
graphics that use the AdobeRGB colorspace. This is also known as the
:ref:`oprgb` standard. The default transfer function is
``V4L2_XFER_FUNC_ADOBERGB``. The default Y'CbCr encoding is
-``V4L2_YCBCR_ENC_601``. The default Y'CbCr quantization is full
-range. The chromaticities of the primary colors and the white reference
-are:
+``V4L2_YCBCR_ENC_601``. The default Y'CbCr quantization is limited
+range.
+
+Note that the :ref:`oprgb` standard specifies full range quantization,
+however all current capture hardware supported by the kernel convert
+R'G'B' to limited range Y'CbCr. So choosing full range as the default
+would break how applications interpret the quantization range.
+The chromaticities of the primary colors and the white reference are:
.. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.7cm}|
@@ -344,7 +355,7 @@ the following ``V4L2_YCBCR_ENC_601`` encoding:
Y' is clamped to the range [0…1] and Cb and Cr are clamped to the range
[-0.5…0.5]. This transform is identical to one defined in SMPTE
-170M/BT.601. The Y'CbCr quantization is full range.
+170M/BT.601. The Y'CbCr quantization is limited range.
.. _col-bt2020:
diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h
index 94f123f3e04e..7f34d3c67648 100644
--- a/include/uapi/linux/videodev2.h
+++ b/include/uapi/linux/videodev2.h
@@ -349,8 +349,8 @@ enum v4l2_quantization {
/*
* The default for R'G'B' quantization is always full range, except
* for the BT2020 colorspace. For Y'CbCr the quantization is always
- * limited range, except for COLORSPACE_JPEG, SRGB, ADOBERGB,
- * XV601 or XV709: those are full range.
+ * limited range, except for COLORSPACE_JPEG, XV601 or XV709: those
+ * are full range.
*/
V4L2_QUANTIZATION_DEFAULT = 0,
V4L2_QUANTIZATION_FULL_RANGE = 1,
@@ -365,8 +365,7 @@ enum v4l2_quantization {
#define V4L2_MAP_QUANTIZATION_DEFAULT(is_rgb, colsp, ycbcr_enc) \
(((is_rgb) && (colsp) == V4L2_COLORSPACE_BT2020) ? V4L2_QUANTIZATION_LIM_RANGE : \
(((is_rgb) || (ycbcr_enc) == V4L2_YCBCR_ENC_XV601 || \
- (ycbcr_enc) == V4L2_YCBCR_ENC_XV709 || (colsp) == V4L2_COLORSPACE_JPEG) || \
- (colsp) == V4L2_COLORSPACE_ADOBERGB || (colsp) == V4L2_COLORSPACE_SRGB ? \
+ (ycbcr_enc) == V4L2_YCBCR_ENC_XV709 || (colsp) == V4L2_COLORSPACE_JPEG) ? \
V4L2_QUANTIZATION_FULL_RANGE : V4L2_QUANTIZATION_LIM_RANGE))
enum v4l2_priority {