1.. Permission is granted to copy, distribute and/or modify this 2.. document under the terms of the GNU Free Documentation License, 3.. Version 1.1 or any later version published by the Free Software 4.. Foundation, with no Invariant Sections, no Front-Cover Texts 5.. and no Back-Cover Texts. A copy of the license is included at 6.. Documentation/userspace-api/media/fdl-appendix.rst. 7.. 8.. TODO: replace it to GFDL-1.1-or-later WITH no-invariant-sections 9 10**************************** 11Defining Colorspaces in V4L2 12**************************** 13 14In V4L2 colorspaces are defined by four values. The first is the 15colorspace identifier (enum :c:type:`v4l2_colorspace`) 16which defines the chromaticities, the default transfer function, the 17default Y'CbCr encoding and the default quantization method. The second 18is the transfer function identifier (enum 19:c:type:`v4l2_xfer_func`) to specify non-standard 20transfer functions. The third is the Y'CbCr encoding identifier (enum 21:c:type:`v4l2_ycbcr_encoding`) to specify 22non-standard Y'CbCr encodings and the fourth is the quantization 23identifier (enum :c:type:`v4l2_quantization`) to 24specify non-standard quantization methods. Most of the time only the 25colorspace field of struct :c:type:`v4l2_pix_format` 26or struct :c:type:`v4l2_pix_format_mplane` 27needs to be filled in. 28 29.. _hsv-colorspace: 30 31On :ref:`HSV formats <hsv-formats>` the *Hue* is defined as the angle on 32the cylindrical color representation. Usually this angle is measured in 33degrees, i.e. 0-360. When we map this angle value into 8 bits, there are 34two basic ways to do it: Divide the angular value by 2 (0-179), or use the 35whole range, 0-255, dividing the angular value by 1.41. The enum 36:c:type:`v4l2_hsv_encoding` specifies which encoding is used. 37 38.. note:: The default R'G'B' quantization is full range for all 39 colorspaces except for BT.2020 which uses limited range R'G'B' 40 quantization. 41 42.. tabularcolumns:: |p{6.7cm}|p{10.8cm}| 43 44.. c:type:: v4l2_colorspace 45 46.. flat-table:: V4L2 Colorspaces 47 :header-rows: 1 48 :stub-columns: 0 49 50 * - Identifier 51 - Details 52 * - ``V4L2_COLORSPACE_DEFAULT`` 53 - The default colorspace. This can be used by applications to let 54 the driver fill in the colorspace. 55 * - ``V4L2_COLORSPACE_SMPTE170M`` 56 - See :ref:`col-smpte-170m`. 57 * - ``V4L2_COLORSPACE_REC709`` 58 - See :ref:`col-rec709`. 59 * - ``V4L2_COLORSPACE_SRGB`` 60 - See :ref:`col-srgb`. 61 * - ``V4L2_COLORSPACE_OPRGB`` 62 - See :ref:`col-oprgb`. 63 * - ``V4L2_COLORSPACE_BT2020`` 64 - See :ref:`col-bt2020`. 65 * - ``V4L2_COLORSPACE_DCI_P3`` 66 - See :ref:`col-dcip3`. 67 * - ``V4L2_COLORSPACE_SMPTE240M`` 68 - See :ref:`col-smpte-240m`. 69 * - ``V4L2_COLORSPACE_470_SYSTEM_M`` 70 - See :ref:`col-sysm`. 71 * - ``V4L2_COLORSPACE_470_SYSTEM_BG`` 72 - See :ref:`col-sysbg`. 73 * - ``V4L2_COLORSPACE_JPEG`` 74 - See :ref:`col-jpeg`. 75 * - ``V4L2_COLORSPACE_RAW`` 76 - The raw colorspace. This is used for raw image capture where the 77 image is minimally processed and is using the internal colorspace 78 of the device. The software that processes an image using this 79 'colorspace' will have to know the internals of the capture 80 device. 81 82 83 84.. c:type:: v4l2_xfer_func 85 86.. tabularcolumns:: |p{5.5cm}|p{12.0cm}| 87 88.. flat-table:: V4L2 Transfer Function 89 :header-rows: 1 90 :stub-columns: 0 91 92 * - Identifier 93 - Details 94 * - ``V4L2_XFER_FUNC_DEFAULT`` 95 - Use the default transfer function as defined by the colorspace. 96 * - ``V4L2_XFER_FUNC_709`` 97 - Use the Rec. 709 transfer function. 98 * - ``V4L2_XFER_FUNC_SRGB`` 99 - Use the sRGB transfer function. 100 * - ``V4L2_XFER_FUNC_OPRGB`` 101 - Use the opRGB transfer function. 102 * - ``V4L2_XFER_FUNC_SMPTE240M`` 103 - Use the SMPTE 240M transfer function. 104 * - ``V4L2_XFER_FUNC_NONE`` 105 - Do not use a transfer function (i.e. use linear RGB values). 106 * - ``V4L2_XFER_FUNC_DCI_P3`` 107 - Use the DCI-P3 transfer function. 108 * - ``V4L2_XFER_FUNC_SMPTE2084`` 109 - Use the SMPTE 2084 transfer function. See :ref:`xf-smpte-2084`. 110 111 112 113.. c:type:: v4l2_ycbcr_encoding 114 115.. tabularcolumns:: |p{7.2cm}|p{10.3cm}| 116 117.. flat-table:: V4L2 Y'CbCr Encodings 118 :header-rows: 1 119 :stub-columns: 0 120 121 * - Identifier 122 - Details 123 * - ``V4L2_YCBCR_ENC_DEFAULT`` 124 - Use the default Y'CbCr encoding as defined by the colorspace. 125 * - ``V4L2_YCBCR_ENC_601`` 126 - Use the BT.601 Y'CbCr encoding. 127 * - ``V4L2_YCBCR_ENC_709`` 128 - Use the Rec. 709 Y'CbCr encoding. 129 * - ``V4L2_YCBCR_ENC_XV601`` 130 - Use the extended gamut xvYCC BT.601 encoding. 131 * - ``V4L2_YCBCR_ENC_XV709`` 132 - Use the extended gamut xvYCC Rec. 709 encoding. 133 * - ``V4L2_YCBCR_ENC_BT2020`` 134 - Use the default non-constant luminance BT.2020 Y'CbCr encoding. 135 * - ``V4L2_YCBCR_ENC_BT2020_CONST_LUM`` 136 - Use the constant luminance BT.2020 Yc'CbcCrc encoding. 137 * - ``V4L2_YCBCR_ENC_SMPTE_240M`` 138 - Use the SMPTE 240M Y'CbCr encoding. 139 140 141 142.. c:type:: v4l2_hsv_encoding 143 144.. tabularcolumns:: |p{6.5cm}|p{11.0cm}| 145 146.. flat-table:: V4L2 HSV Encodings 147 :header-rows: 1 148 :stub-columns: 0 149 150 * - Identifier 151 - Details 152 * - ``V4L2_HSV_ENC_180`` 153 - For the Hue, each LSB is two degrees. 154 * - ``V4L2_HSV_ENC_256`` 155 - For the Hue, the 360 degrees are mapped into 8 bits, i.e. each 156 LSB is roughly 1.41 degrees. 157 158 159 160.. c:type:: v4l2_quantization 161 162.. tabularcolumns:: |p{6.5cm}|p{11.0cm}| 163 164.. flat-table:: V4L2 Quantization Methods 165 :header-rows: 1 166 :stub-columns: 0 167 168 * - Identifier 169 - Details 170 * - ``V4L2_QUANTIZATION_DEFAULT`` 171 - Use the default quantization encoding as defined by the 172 colorspace. This is always full range for R'G'B' (except for the 173 BT.2020 colorspace) and HSV. It is usually limited range for Y'CbCr. 174 * - ``V4L2_QUANTIZATION_FULL_RANGE`` 175 - Use the full range quantization encoding. I.e. the range [0…1] is 176 mapped to [0…255] (with possible clipping to [1…254] to avoid the 177 0x00 and 0xff values). Cb and Cr are mapped from [-0.5…0.5] to 178 [0…255] (with possible clipping to [1…254] to avoid the 0x00 and 179 0xff values). 180 * - ``V4L2_QUANTIZATION_LIM_RANGE`` 181 - Use the limited range quantization encoding. I.e. the range [0…1] 182 is mapped to [16…235]. Cb and Cr are mapped from [-0.5…0.5] to 183 [16…240]. 184