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/media/uapi/fdl-appendix.rst.
8 .. TODO: replace it to GFDL-1.1-or-later WITH no-invariant-sections
10 .. _v4l2-meta-fmt-vsp1-hgt:
12 *******************************
13 V4L2_META_FMT_VSP1_HGT ('VSPT')
14 *******************************
16 Renesas R-Car VSP1 2-D Histogram Data
22 This format describes histogram data generated by the Renesas R-Car VSP1
23 2-D Histogram (HGT) engine.
25 The VSP1 HGT is a histogram computation engine that operates on HSV
26 data. It operates on a possibly cropped and subsampled input image and
27 computes the sum, maximum and minimum of the S component as well as a
28 weighted frequency histogram based on the H and S components.
30 The histogram is a matrix of 6 Hue and 32 Saturation buckets, 192 in
31 total. Each HSV value is added to one or more buckets with a weight
32 between 1 and 16 depending on the Hue areas configuration. Finding the
33 corresponding buckets is done by inspecting the H and S value independently.
35 The Saturation position **n** (0 - 31) of the bucket in the matrix is
36 found by the expression:
40 The Hue position **m** (0 - 5) of the bucket in the matrix depends on
41 how the HGT Hue areas are configured. There are 6 user configurable Hue
42 Areas which can be configured to cover overlapping Hue values:
46 Area 0 Area 1 Area 2 Area 3 Area 4 Area 5
47 ________ ________ ________ ________ ________ ________
48 \ /| |\ /| |\ /| |\ /| |\ /| |\ /| |\ /
49 \ / | | \ / | | \ / | | \ / | | \ / | | \ / | | \ /
50 X | | X | | X | | X | | X | | X | | X
51 / \ | | / \ | | / \ | | / \ | | / \ | | / \ | | / \
52 / \| |/ \| |/ \| |/ \| |/ \| |/ \| |/ \
53 5U 0L 0U 1L 1U 2L 2U 3L 3U 4L 4U 5L 5U 0L
54 <0..............................Hue Value............................255>
56 When two consecutive areas don't overlap (n+1L is equal to nU) the boundary
57 value is considered as part of the lower area.
59 Pixels with a hue value included in the centre of an area (between nL and nU
60 included) are attributed to that single area and given a weight of 16. Pixels
61 with a hue value included in the overlapping region between two areas (between
62 n+1L and nU excluded) are attributed to both areas and given a weight for each
63 of these areas proportional to their position along the diagonal lines
66 The Hue area setup must match one of the following constrains:
70 0L <= 0U <= 1L <= 1U <= 2L <= 2U <= 3L <= 3U <= 4L <= 4U <= 5L <= 5U
74 0U <= 1L <= 1U <= 2L <= 2U <= 3L <= 3U <= 4L <= 4U <= 5L <= 5U <= 0L
77 All data is stored in memory in little endian format. Each cell in the tables
80 .. flat-table:: VSP1 HGT Data - (776 bytes)
97 - :cspan:`4` S sum [31:0]
99 - :cspan:`4` Histogram bucket (m=0, n=0) [31:0]
101 - :cspan:`4` Histogram bucket (m=0, n=1) [31:0]
105 - :cspan:`4` Histogram bucket (m=0, n=31) [31:0]
107 - :cspan:`4` Histogram bucket (m=1, n=0) [31:0]
111 - :cspan:`4` Histogram bucket (m=2, n=0) [31:0]
115 - :cspan:`4` Histogram bucket (m=3, n=0) [31:0]
119 - :cspan:`4` Histogram bucket (m=4, n=0) [31:0]
123 - :cspan:`4` Histogram bucket (m=5, n=0) [31:0]
127 - :cspan:`4` Histogram bucket (m=5, n=31) [31:0]