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[media] videodev2.h: go back to limited range Y'CbCr for SRGB and, ADOBERGB

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This reverts 'commit 7e0739cd9c ("[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: 7e0739cd9c ("[media] videodev2.h: fix sYCC/AdobeYCC default quantization range")
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Cc: <stable@vger.kernel.org>      # for v4.9 and up
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
This commit is contained in:
Hans Verkuil 2017-02-10 07:18:36 -02:00 committed by Mauro Carvalho Chehab
parent f9f96fc10c
commit 35879ee476
2 changed files with 20 additions and 10 deletions
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23
Documentation/media/uapi/v4l/pixfmt-007.rst
View File

@ -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:

7
include/uapi/linux/videodev2.h
View File

@ -362,8 +362,8 @@ 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,
@ -379,8 +379,7 @@ enum v4l2_quantization {
(((is_rgb_or_hsv) && (colsp) == V4L2_COLORSPACE_BT2020) ? \
V4L2_QUANTIZATION_LIM_RANGE : \
(((is_rgb_or_hsv) || (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 {