diff options
| -rw-r--r-- | Documentation/media/uapi/v4l/pixfmt-007.rst | 23 | ||||
| -rw-r--r-- | include/uapi/linux/videodev2.h | 7 |
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 { |