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1.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later2 3.. _v4l2-meta-fmt-vsp1-hgt:4 5*******************************6V4L2_META_FMT_VSP1_HGT ('VSPT')7*******************************8 9Renesas R-Car VSP1 2-D Histogram Data10 11 12Description13===========14 15This format describes histogram data generated by the Renesas R-Car VSP1162-D Histogram (HGT) engine.17 18The VSP1 HGT is a histogram computation engine that operates on HSV19data. It operates on a possibly cropped and subsampled input image and20computes the sum, maximum and minimum of the S component as well as a21weighted frequency histogram based on the H and S components.22 23The histogram is a matrix of 6 Hue and 32 Saturation buckets, 192 in24total. Each HSV value is added to one or more buckets with a weight25between 1 and 16 depending on the Hue areas configuration. Finding the26corresponding buckets is done by inspecting the H and S value independently.27 28The Saturation position **n** (0 - 31) of the bucket in the matrix is29found by the expression:30 31 n = S / 832 33The Hue position **m** (0 - 5) of the bucket in the matrix depends on34how the HGT Hue areas are configured. There are 6 user configurable Hue35Areas which can be configured to cover overlapping Hue values:36 37.. raw:: latex38 39 \small40 41::42 43 Area 0 Area 1 Area 2 Area 3 Area 4 Area 544 ________ ________ ________ ________ ________ ________45 \ /| |\ /| |\ /| |\ /| |\ /| |\ /| |\ /46 \ / | | \ / | | \ / | | \ / | | \ / | | \ / | | \ /47 X | | X | | X | | X | | X | | X | | X48 / \ | | / \ | | / \ | | / \ | | / \ | | / \ | | / \49 / \| |/ \| |/ \| |/ \| |/ \| |/ \| |/ \50 5U 0L 0U 1L 1U 2L 2U 3L 3U 4L 4U 5L 5U 0L51 <0..............................Hue Value............................255>52 53 54.. raw:: latex55 56 \normalsize57 58When two consecutive areas don't overlap (n+1L is equal to nU) the boundary59value is considered as part of the lower area.60 61Pixels with a hue value included in the centre of an area (between nL and nU62included) are attributed to that single area and given a weight of 16. Pixels63with a hue value included in the overlapping region between two areas (between64n+1L and nU excluded) are attributed to both areas and given a weight for each65of these areas proportional to their position along the diagonal lines66(rounded down).67 68The Hue area setup must match one of the following constrains:69 70::71 72 0L <= 0U <= 1L <= 1U <= 2L <= 2U <= 3L <= 3U <= 4L <= 4U <= 5L <= 5U73 74::75 76 0U <= 1L <= 1U <= 2L <= 2U <= 3L <= 3U <= 4L <= 4U <= 5L <= 5U <= 0L77 78**Byte Order.**79All data is stored in memory in little endian format. Each cell in the tables80contains one byte.81 82.. flat-table:: VSP1 HGT Data - (776 bytes)83 :header-rows: 284 :stub-columns: 085 86 * - Offset87 - :cspan:`4` Memory88 * -89 - [31:24]90 - [23:16]91 - [15:8]92 - [7:0]93 * - 094 - -95 - S max [7:0]96 - -97 - S min [7:0]98 * - 499 - :cspan:`4` S sum [31:0]100 * - 8101 - :cspan:`4` Histogram bucket (m=0, n=0) [31:0]102 * - 12103 - :cspan:`4` Histogram bucket (m=0, n=1) [31:0]104 * -105 - :cspan:`4` ...106 * - 132107 - :cspan:`4` Histogram bucket (m=0, n=31) [31:0]108 * - 136109 - :cspan:`4` Histogram bucket (m=1, n=0) [31:0]110 * -111 - :cspan:`4` ...112 * - 264113 - :cspan:`4` Histogram bucket (m=2, n=0) [31:0]114 * -115 - :cspan:`4` ...116 * - 392117 - :cspan:`4` Histogram bucket (m=3, n=0) [31:0]118 * -119 - :cspan:`4` ...120 * - 520121 - :cspan:`4` Histogram bucket (m=4, n=0) [31:0]122 * -123 - :cspan:`4` ...124 * - 648125 - :cspan:`4` Histogram bucket (m=5, n=0) [31:0]126 * -127 - :cspan:`4` ...128 * - 772129 - :cspan:`4` Histogram bucket (m=5, n=31) [31:0]130