diff options
Diffstat (limited to 'Documentation/media/uapi/v4l/pixfmt-007.rst')
-rw-r--r-- | Documentation/media/uapi/v4l/pixfmt-007.rst | 894 |
1 files changed, 894 insertions, 0 deletions
diff --git a/Documentation/media/uapi/v4l/pixfmt-007.rst b/Documentation/media/uapi/v4l/pixfmt-007.rst new file mode 100644 index 0000000..5e39cda --- /dev/null +++ b/Documentation/media/uapi/v4l/pixfmt-007.rst @@ -0,0 +1,894 @@ +.. -*- coding: utf-8; mode: rst -*- + +******************************** +Detailed Colorspace Descriptions +******************************** + + +.. _col-smpte-170m: + +Colorspace SMPTE 170M (V4L2_COLORSPACE_SMPTE170M) +================================================= + +The :ref:`smpte170m` standard defines the colorspace used by NTSC and +PAL and by SDTV in general. The default transfer function is +``V4L2_XFER_FUNC_709``. The default Y'CbCr encoding is +``V4L2_YCBCR_ENC_601``. The default Y'CbCr quantization is limited +range. The chromaticities of the primary colors and the white reference +are: + + + +.. flat-table:: SMPTE 170M Chromaticities + :header-rows: 1 + :stub-columns: 0 + :widths: 1 1 2 + + + - .. row 1 + + - Color + + - x + + - y + + - .. row 2 + + - Red + + - 0.630 + + - 0.340 + + - .. row 3 + + - Green + + - 0.310 + + - 0.595 + + - .. row 4 + + - Blue + + - 0.155 + + - 0.070 + + - .. row 5 + + - White Reference (D65) + + - 0.3127 + + - 0.3290 + + +The red, green and blue chromaticities are also often referred to as the +SMPTE C set, so this colorspace is sometimes called SMPTE C as well. + +The transfer function defined for SMPTE 170M is the same as the one +defined in Rec. 709. + + L' = -1.099(-L) :sup:`0.45` + 0.099 for L ≤ -0.018 + + L' = 4.5L for -0.018 < L < 0.018 + + L' = 1.099L :sup:`0.45` - 0.099 for L ≥ 0.018 + +Inverse Transfer function: + + L = -((L' - 0.099) / -1.099) :sup:`1/0.45` for L' ≤ -0.081 + + L = L' / 4.5 for -0.081 < L' < 0.081 + + L = ((L' + 0.099) / 1.099) :sup:`1/0.45` for L' ≥ 0.081 + +The luminance (Y') and color difference (Cb and Cr) are obtained with +the following ``V4L2_YCBCR_ENC_601`` encoding: + + Y' = 0.299R' + 0.587G' + 0.114B' + + Cb = -0.169R' - 0.331G' + 0.5B' + + Cr = 0.5R' - 0.419G' - 0.081B' + +Y' is clamped to the range [0…1] and Cb and Cr are clamped to the range +[-0.5…0.5]. This conversion to Y'CbCr is identical to the one defined in +the :ref:`itu601` standard and this colorspace is sometimes called +BT.601 as well, even though BT.601 does not mention any color primaries. + +The default quantization is limited range, but full range is possible +although rarely seen. + + +.. _col-rec709: + +Colorspace Rec. 709 (V4L2_COLORSPACE_REC709) +============================================ + +The :ref:`itu709` standard defines the colorspace used by HDTV in +general. The default transfer function is ``V4L2_XFER_FUNC_709``. The +default Y'CbCr encoding is ``V4L2_YCBCR_ENC_709``. The default Y'CbCr +quantization is limited range. The chromaticities of the primary colors +and the white reference are: + + + +.. flat-table:: Rec. 709 Chromaticities + :header-rows: 1 + :stub-columns: 0 + :widths: 1 1 2 + + + - .. row 1 + + - Color + + - x + + - y + + - .. row 2 + + - Red + + - 0.640 + + - 0.330 + + - .. row 3 + + - Green + + - 0.300 + + - 0.600 + + - .. row 4 + + - Blue + + - 0.150 + + - 0.060 + + - .. row 5 + + - White Reference (D65) + + - 0.3127 + + - 0.3290 + + +The full name of this standard is Rec. ITU-R BT.709-5. + +Transfer function. Normally L is in the range [0…1], but for the +extended gamut xvYCC encoding values outside that range are allowed. + + L' = -1.099(-L) :sup:`0.45` + 0.099 for L ≤ -0.018 + + L' = 4.5L for -0.018 < L < 0.018 + + L' = 1.099L :sup:`0.45` - 0.099 for L ≥ 0.018 + +Inverse Transfer function: + + L = -((L' - 0.099) / -1.099) :sup:`1/0.45` for L' ≤ -0.081 + + L = L' / 4.5 for -0.081 < L' < 0.081 + + L = ((L' + 0.099) / 1.099) :sup:`1/0.45` for L' ≥ 0.081 + +The luminance (Y') and color difference (Cb and Cr) are obtained with +the following ``V4L2_YCBCR_ENC_709`` encoding: + + Y' = 0.2126R' + 0.7152G' + 0.0722B' + + Cb = -0.1146R' - 0.3854G' + 0.5B' + + Cr = 0.5R' - 0.4542G' - 0.0458B' + +Y' is clamped to the range [0…1] and Cb and Cr are clamped to the range +[-0.5…0.5]. + +The default quantization is limited range, but full range is possible +although rarely seen. + +The ``V4L2_YCBCR_ENC_709`` encoding described above is the default for +this colorspace, but it can be overridden with ``V4L2_YCBCR_ENC_601``, +in which case the BT.601 Y'CbCr encoding is used. + +Two additional extended gamut Y'CbCr encodings are also possible with +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: + + Y' = (219 / 256) * (0.2126R' + 0.7152G' + 0.0722B') + (16 / 256) + + Cb = (224 / 256) * (-0.1146R' - 0.3854G' + 0.5B') + + Cr = (224 / 256) * (0.5R' - 0.4542G' - 0.0458B') + +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: + + Y' = (219 / 256) * (0.299R' + 0.587G' + 0.114B') + (16 / 256) + + Cb = (224 / 256) * (-0.169R' - 0.331G' + 0.5B') + + Cr = (224 / 256) * (0.5R' - 0.419G' - 0.081B') + +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 +used by selecting ``V4L2_YCBCR_ENC_XV709`` or ``V4L2_YCBCR_ENC_XV601``. +The xvYCC encodings always use full range quantization. + + +.. _col-srgb: + +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_SYCC``. The default Y'CbCr quantization is full range. +The chromaticities of the primary colors and the white reference are: + + + +.. flat-table:: sRGB Chromaticities + :header-rows: 1 + :stub-columns: 0 + :widths: 1 1 2 + + + - .. row 1 + + - Color + + - x + + - y + + - .. row 2 + + - Red + + - 0.640 + + - 0.330 + + - .. row 3 + + - Green + + - 0.300 + + - 0.600 + + - .. row 4 + + - Blue + + - 0.150 + + - 0.060 + + - .. row 5 + + - White Reference (D65) + + - 0.3127 + + - 0.3290 + + +These chromaticities are identical to the Rec. 709 colorspace. + +Transfer function. Note that negative values for L are only used by the +Y'CbCr conversion. + + L' = -1.055(-L) :sup:`1/2.4` + 0.055 for L < -0.0031308 + + L' = 12.92L for -0.0031308 ≤ L ≤ 0.0031308 + + L' = 1.055L :sup:`1/2.4` - 0.055 for 0.0031308 < L ≤ 1 + +Inverse Transfer function: + + L = -((-L' + 0.055) / 1.055) :sup:`2.4` for L' < -0.04045 + + L = L' / 12.92 for -0.04045 ≤ L' ≤ 0.04045 + + L = ((L' + 0.055) / 1.055) :sup:`2.4` for L' > 0.04045 + +The luminance (Y') and color difference (Cb and Cr) are obtained with +the following ``V4L2_YCBCR_ENC_SYCC`` encoding as defined by +:ref:`sycc`: + + Y' = 0.2990R' + 0.5870G' + 0.1140B' + + Cb = -0.1687R' - 0.3313G' + 0.5B' + + Cr = 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 ``V4L2_YCBCR_ENC_SYCC`` quantization is always full +range. Although this Y'CbCr encoding looks very similar to the +``V4L2_YCBCR_ENC_XV601`` encoding, it is not. The +``V4L2_YCBCR_ENC_XV601`` scales and offsets the Y'CbCr values before +quantization, but this encoding does not do that. + + +.. _col-adobergb: + +Colorspace Adobe RGB (V4L2_COLORSPACE_ADOBERGB) +=============================================== + +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 limited +range. The chromaticities of the primary colors and the white reference +are: + + + +.. flat-table:: Adobe RGB Chromaticities + :header-rows: 1 + :stub-columns: 0 + :widths: 1 1 2 + + + - .. row 1 + + - Color + + - x + + - y + + - .. row 2 + + - Red + + - 0.6400 + + - 0.3300 + + - .. row 3 + + - Green + + - 0.2100 + + - 0.7100 + + - .. row 4 + + - Blue + + - 0.1500 + + - 0.0600 + + - .. row 5 + + - White Reference (D65) + + - 0.3127 + + - 0.3290 + + + +Transfer function: + + L' = L :sup:`1/2.19921875` + +Inverse Transfer function: + + L = L' :sup:`2.19921875` + +The luminance (Y') and color difference (Cb and Cr) are obtained with +the following ``V4L2_YCBCR_ENC_601`` encoding: + + Y' = 0.299R' + 0.587G' + 0.114B' + + Cb = -0.169R' - 0.331G' + 0.5B' + + Cr = 0.5R' - 0.419G' - 0.081B' + +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 limited range. + + +.. _col-bt2020: + +Colorspace BT.2020 (V4L2_COLORSPACE_BT2020) +=========================================== + +The :ref:`itu2020` standard defines the colorspace used by Ultra-high +definition television (UHDTV). The default transfer function is +``V4L2_XFER_FUNC_709``. The default Y'CbCr encoding is +``V4L2_YCBCR_ENC_BT2020``. The default R'G'B' quantization is limited +range (!), and so is the default Y'CbCr quantization. The chromaticities +of the primary colors and the white reference are: + + + +.. flat-table:: BT.2020 Chromaticities + :header-rows: 1 + :stub-columns: 0 + :widths: 1 1 2 + + + - .. row 1 + + - Color + + - x + + - y + + - .. row 2 + + - Red + + - 0.708 + + - 0.292 + + - .. row 3 + + - Green + + - 0.170 + + - 0.797 + + - .. row 4 + + - Blue + + - 0.131 + + - 0.046 + + - .. row 5 + + - White Reference (D65) + + - 0.3127 + + - 0.3290 + + + +Transfer function (same as Rec. 709): + + L' = 4.5L for 0 ≤ L < 0.018 + + L' = 1.099L :sup:`0.45` - 0.099 for 0.018 ≤ L ≤ 1 + +Inverse Transfer function: + + L = L' / 4.5 for L' < 0.081 + + L = ((L' + 0.099) / 1.099) :sup:`1/0.45` for L' ≥ 0.081 + +The luminance (Y') and color difference (Cb and Cr) are obtained with +the following ``V4L2_YCBCR_ENC_BT2020`` encoding: + + Y' = 0.2627R' + 0.6780G' + 0.0593B' + + Cb = -0.1396R' - 0.3604G' + 0.5B' + + Cr = 0.5R' - 0.4598G' - 0.0402B' + +Y' is clamped to the range [0…1] and Cb and Cr are clamped to the range +[-0.5…0.5]. The Y'CbCr quantization is limited range. + +There is also an alternate constant luminance R'G'B' to Yc'CbcCrc +(``V4L2_YCBCR_ENC_BT2020_CONST_LUM``) encoding: + +Luma: + + Yc' = (0.2627R + 0.6780G + 0.0593B)' + +B' - Yc' ≤ 0: + + Cbc = (B' - Yc') / 1.9404 + +B' - Yc' > 0: + + Cbc = (B' - Yc') / 1.5816 + +R' - Yc' ≤ 0: + + Crc = (R' - Y') / 1.7184 + +R' - Yc' > 0: + + Crc = (R' - Y') / 0.9936 + +Yc' is clamped to the range [0…1] and Cbc and Crc are clamped to the +range [-0.5…0.5]. The Yc'CbcCrc quantization is limited range. + + +.. _col-dcip3: + +Colorspace DCI-P3 (V4L2_COLORSPACE_DCI_P3) +========================================== + +The :ref:`smpte431` standard defines the colorspace used by cinema +projectors that use the DCI-P3 colorspace. The default transfer function +is ``V4L2_XFER_FUNC_DCI_P3``. The default Y'CbCr encoding is +``V4L2_YCBCR_ENC_709``. Note that this colorspace does not specify a +Y'CbCr encoding since it is not meant to be encoded to Y'CbCr. So this +default Y'CbCr encoding was picked because it is the HDTV encoding. The +default Y'CbCr quantization is limited range. The chromaticities of the +primary colors and the white reference are: + + + +.. flat-table:: DCI-P3 Chromaticities + :header-rows: 1 + :stub-columns: 0 + :widths: 1 1 2 + + + - .. row 1 + + - Color + + - x + + - y + + - .. row 2 + + - Red + + - 0.6800 + + - 0.3200 + + - .. row 3 + + - Green + + - 0.2650 + + - 0.6900 + + - .. row 4 + + - Blue + + - 0.1500 + + - 0.0600 + + - .. row 5 + + - White Reference + + - 0.3140 + + - 0.3510 + + + +Transfer function: + + L' = L :sup:`1/2.6` + +Inverse Transfer function: + + L = L' :sup:`2.6` + +Y'CbCr encoding is not specified. V4L2 defaults to Rec. 709. + + +.. _col-smpte-240m: + +Colorspace SMPTE 240M (V4L2_COLORSPACE_SMPTE240M) +================================================= + +The :ref:`smpte240m` standard was an interim standard used during the +early days of HDTV (1988-1998). It has been superseded by Rec. 709. The +default transfer function is ``V4L2_XFER_FUNC_SMPTE240M``. The default +Y'CbCr encoding is ``V4L2_YCBCR_ENC_SMPTE240M``. The default Y'CbCr +quantization is limited range. The chromaticities of the primary colors +and the white reference are: + + + +.. flat-table:: SMPTE 240M Chromaticities + :header-rows: 1 + :stub-columns: 0 + :widths: 1 1 2 + + + - .. row 1 + + - Color + + - x + + - y + + - .. row 2 + + - Red + + - 0.630 + + - 0.340 + + - .. row 3 + + - Green + + - 0.310 + + - 0.595 + + - .. row 4 + + - Blue + + - 0.155 + + - 0.070 + + - .. row 5 + + - White Reference (D65) + + - 0.3127 + + - 0.3290 + + +These chromaticities are identical to the SMPTE 170M colorspace. + +Transfer function: + + L' = 4L for 0 ≤ L < 0.0228 + + L' = 1.1115L :sup:`0.45` - 0.1115 for 0.0228 ≤ L ≤ 1 + +Inverse Transfer function: + + L = L' / 4 for 0 ≤ L' < 0.0913 + + L = ((L' + 0.1115) / 1.1115) :sup:`1/0.45` for L' ≥ 0.0913 + +The luminance (Y') and color difference (Cb and Cr) are obtained with +the following ``V4L2_YCBCR_ENC_SMPTE240M`` encoding: + + Y' = 0.2122R' + 0.7013G' + 0.0865B' + + Cb = -0.1161R' - 0.3839G' + 0.5B' + + Cr = 0.5R' - 0.4451G' - 0.0549B' + +Yc' is clamped to the range [0…1] and Cbc and Crc are clamped to the +range [-0.5…0.5]. The Y'CbCr quantization is limited range. + + +.. _col-sysm: + +Colorspace NTSC 1953 (V4L2_COLORSPACE_470_SYSTEM_M) +=================================================== + +This standard defines the colorspace used by NTSC in 1953. In practice +this colorspace is obsolete and SMPTE 170M should be used instead. The +default transfer function is ``V4L2_XFER_FUNC_709``. The default Y'CbCr +encoding is ``V4L2_YCBCR_ENC_601``. The default Y'CbCr quantization is +limited range. The chromaticities of the primary colors and the white +reference are: + + + +.. flat-table:: NTSC 1953 Chromaticities + :header-rows: 1 + :stub-columns: 0 + :widths: 1 1 2 + + + - .. row 1 + + - Color + + - x + + - y + + - .. row 2 + + - Red + + - 0.67 + + - 0.33 + + - .. row 3 + + - Green + + - 0.21 + + - 0.71 + + - .. row 4 + + - Blue + + - 0.14 + + - 0.08 + + - .. row 5 + + - White Reference (C) + + - 0.310 + + - 0.316 + + +Note that this colorspace uses Illuminant C instead of D65 as the white +reference. To correctly convert an image in this colorspace to another +that uses D65 you need to apply a chromatic adaptation algorithm such as +the Bradford method. + +The transfer function was never properly defined for NTSC 1953. The Rec. +709 transfer function is recommended in the literature: + + L' = 4.5L for 0 ≤ L < 0.018 + + L' = 1.099L :sup:`0.45` - 0.099 for 0.018 ≤ L ≤ 1 + +Inverse Transfer function: + + L = L' / 4.5 for L' < 0.081 + + L = ((L' + 0.099) / 1.099) :sup:`1/0.45` for L' ≥ 0.081 + +The luminance (Y') and color difference (Cb and Cr) are obtained with +the following ``V4L2_YCBCR_ENC_601`` encoding: + + Y' = 0.299R' + 0.587G' + 0.114B' + + Cb = -0.169R' - 0.331G' + 0.5B' + + Cr = 0.5R' - 0.419G' - 0.081B' + +Y' is clamped to the range [0…1] and Cb and Cr are clamped to the range +[-0.5…0.5]. The Y'CbCr quantization is limited range. This transform is +identical to one defined in SMPTE 170M/BT.601. + + +.. _col-sysbg: + +Colorspace EBU Tech. 3213 (V4L2_COLORSPACE_470_SYSTEM_BG) +========================================================= + +The :ref:`tech3213` standard defines the colorspace used by PAL/SECAM +in 1975. In practice this colorspace is obsolete and SMPTE 170M should +be used instead. The default transfer function is +``V4L2_XFER_FUNC_709``. The default Y'CbCr encoding is +``V4L2_YCBCR_ENC_601``. The default Y'CbCr quantization is limited +range. The chromaticities of the primary colors and the white reference +are: + + + +.. flat-table:: EBU Tech. 3213 Chromaticities + :header-rows: 1 + :stub-columns: 0 + :widths: 1 1 2 + + + - .. row 1 + + - Color + + - x + + - y + + - .. row 2 + + - Red + + - 0.64 + + - 0.33 + + - .. row 3 + + - Green + + - 0.29 + + - 0.60 + + - .. row 4 + + - Blue + + - 0.15 + + - 0.06 + + - .. row 5 + + - White Reference (D65) + + - 0.3127 + + - 0.3290 + + + +The transfer function was never properly defined for this colorspace. +The Rec. 709 transfer function is recommended in the literature: + + L' = 4.5L for 0 ≤ L < 0.018 + + L' = 1.099L :sup:`0.45` - 0.099 for 0.018 ≤ L ≤ 1 + +Inverse Transfer function: + + L = L' / 4.5 for L' < 0.081 + + L = ((L' + 0.099) / 1.099) :sup:`1/0.45` for L' ≥ 0.081 + +The luminance (Y') and color difference (Cb and Cr) are obtained with +the following ``V4L2_YCBCR_ENC_601`` encoding: + + Y' = 0.299R' + 0.587G' + 0.114B' + + Cb = -0.169R' - 0.331G' + 0.5B' + + Cr = 0.5R' - 0.419G' - 0.081B' + +Y' is clamped to the range [0…1] and Cb and Cr are clamped to the range +[-0.5…0.5]. The Y'CbCr quantization is limited range. This transform is +identical to one defined in SMPTE 170M/BT.601. + + +.. _col-jpeg: + +Colorspace JPEG (V4L2_COLORSPACE_JPEG) +====================================== + +This colorspace defines the colorspace used by most (Motion-)JPEG +formats. The chromaticities of the primary colors and the white +reference are identical to sRGB. The transfer function use is +``V4L2_XFER_FUNC_SRGB``. The Y'CbCr encoding is ``V4L2_YCBCR_ENC_601`` +with full range quantization where Y' is scaled to [0…255] and Cb/Cr are +scaled to [-128…128] and then clipped to [-128…127]. + +Note that the JPEG standard does not actually store colorspace +information. So if something other than sRGB is used, then the driver +will have to set that information explicitly. Effectively +``V4L2_COLORSPACE_JPEG`` can be considered to be an abbreviation for +``V4L2_COLORSPACE_SRGB``, ``V4L2_YCBCR_ENC_601`` and +``V4L2_QUANTIZATION_FULL_RANGE``. |