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diff --git a/Documentation/userspace-api/media/v4l/pixfmt-meta-vsp1-hgt.rst b/Documentation/userspace-api/media/v4l/pixfmt-meta-vsp1-hgt.rst new file mode 100644 index 000000000..d8830ff60 --- /dev/null +++ b/Documentation/userspace-api/media/v4l/pixfmt-meta-vsp1-hgt.rst @@ -0,0 +1,129 @@ +.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later + +.. _v4l2-meta-fmt-vsp1-hgt: + +******************************* +V4L2_META_FMT_VSP1_HGT ('VSPT') +******************************* + +Renesas R-Car VSP1 2-D Histogram Data + + +Description +=========== + +This format describes histogram data generated by the Renesas R-Car VSP1 +2-D Histogram (HGT) engine. + +The VSP1 HGT is a histogram computation engine that operates on HSV +data. It operates on a possibly cropped and subsampled input image and +computes the sum, maximum and minimum of the S component as well as a +weighted frequency histogram based on the H and S components. + +The histogram is a matrix of 6 Hue and 32 Saturation buckets, 192 in +total. Each HSV value is added to one or more buckets with a weight +between 1 and 16 depending on the Hue areas configuration. Finding the +corresponding buckets is done by inspecting the H and S value independently. + +The Saturation position **n** (0 - 31) of the bucket in the matrix is +found by the expression: + + n = S / 8 + +The Hue position **m** (0 - 5) of the bucket in the matrix depends on +how the HGT Hue areas are configured. There are 6 user configurable Hue +Areas which can be configured to cover overlapping Hue values: + +.. raw:: latex + + \small + +:: + + Area 0 Area 1 Area 2 Area 3 Area 4 Area 5 + ________ ________ ________ ________ ________ ________ + \ /| |\ /| |\ /| |\ /| |\ /| |\ /| |\ / + \ / | | \ / | | \ / | | \ / | | \ / | | \ / | | \ / + X | | X | | X | | X | | X | | X | | X + / \ | | / \ | | / \ | | / \ | | / \ | | / \ | | / \ + / \| |/ \| |/ \| |/ \| |/ \| |/ \| |/ \ + 5U 0L 0U 1L 1U 2L 2U 3L 3U 4L 4U 5L 5U 0L + <0..............................Hue Value............................255> + + +.. raw:: latex + + \normalsize + +When two consecutive areas don't overlap (n+1L is equal to nU) the boundary +value is considered as part of the lower area. + +Pixels with a hue value included in the centre of an area (between nL and nU +included) are attributed to that single area and given a weight of 16. Pixels +with a hue value included in the overlapping region between two areas (between +n+1L and nU excluded) are attributed to both areas and given a weight for each +of these areas proportional to their position along the diagonal lines +(rounded down). + +The Hue area setup must match one of the following constrains: + +:: + + 0L <= 0U <= 1L <= 1U <= 2L <= 2U <= 3L <= 3U <= 4L <= 4U <= 5L <= 5U + +:: + + 0U <= 1L <= 1U <= 2L <= 2U <= 3L <= 3U <= 4L <= 4U <= 5L <= 5U <= 0L + +**Byte Order.** +All data is stored in memory in little endian format. Each cell in the tables +contains one byte. + +.. flat-table:: VSP1 HGT Data - (776 bytes) + :header-rows: 2 + :stub-columns: 0 + + * - Offset + - :cspan:`4` Memory + * - + - [31:24] + - [23:16] + - [15:8] + - [7:0] + * - 0 + - - + - S max [7:0] + - - + - S min [7:0] + * - 4 + - :cspan:`4` S sum [31:0] + * - 8 + - :cspan:`4` Histogram bucket (m=0, n=0) [31:0] + * - 12 + - :cspan:`4` Histogram bucket (m=0, n=1) [31:0] + * - + - :cspan:`4` ... + * - 132 + - :cspan:`4` Histogram bucket (m=0, n=31) [31:0] + * - 136 + - :cspan:`4` Histogram bucket (m=1, n=0) [31:0] + * - + - :cspan:`4` ... + * - 264 + - :cspan:`4` Histogram bucket (m=2, n=0) [31:0] + * - + - :cspan:`4` ... + * - 392 + - :cspan:`4` Histogram bucket (m=3, n=0) [31:0] + * - + - :cspan:`4` ... + * - 520 + - :cspan:`4` Histogram bucket (m=4, n=0) [31:0] + * - + - :cspan:`4` ... + * - 648 + - :cspan:`4` Histogram bucket (m=5, n=0) [31:0] + * - + - :cspan:`4` ... + * - 772 + - :cspan:`4` Histogram bucket (m=5, n=31) [31:0] |