xref: /kernel/linux/linux-6.6/Documentation/userspace-api/media/v4l/metafmt-vsp1-hgo.rst

.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later

.. _v4l2-meta-fmt-vsp1-hgo:

*******************************
V4L2_META_FMT_VSP1_HGO ('VSPH')
*******************************

Renesas R-Car VSP1 1-D Histogram Data


Description
===========

This format describes histogram data generated by the Renesas R-Car VSP1 1-D
Histogram (HGO) engine.

The VSP1 HGO is a histogram computation engine that can operate on RGB, YCrCb
or HSV data. It operates on a possibly cropped and subsampled input image and
computes the minimum, maximum and sum of all pixels as well as per-channel
histograms.

The HGO can compute histograms independently per channel, on the maximum of the
three channels (RGB data only) or on the Y channel only (YCbCr only). It can
additionally output the histogram with 64 or 256 bins, resulting in four
possible modes of operation.

- In *64 bins normal mode*, the HGO operates on the three channels independently
  to compute three 64-bins histograms. RGB, YCbCr and HSV image formats are
  supported.
- In *64 bins maximum mode*, the HGO operates on the maximum of the (R, G, B)
  channels to compute a single 64-bins histogram. Only the RGB image format is
  supported.
- In *256 bins normal mode*, the HGO operates on the Y channel to compute a
  single 256-bins histogram. Only the YCbCr image format is supported.
- In *256 bins maximum mode*, the HGO operates on the maximum of the (R, G, B)
  channels to compute a single 256-bins histogram. Only the RGB image format is
  supported.

**Byte Order.**
All data is stored in memory in little endian format. Each cell in the tables
contains one byte.

.. flat-table:: VSP1 HGO Data - 64 Bins, Normal Mode (792 bytes)
    :header-rows:  2
    :stub-columns: 0

    * - Offset
      - :cspan:`4` Memory
    * -
      - [31:24]
      - [23:16]
      - [15:8]
      - [7:0]
    * - 0
      -
      - R/Cr/H max [7:0]
      -
      - R/Cr/H min [7:0]
    * - 4
      -
      - G/Y/S max [7:0]
      -
      - G/Y/S min [7:0]
    * - 8
      -
      - B/Cb/V max [7:0]
      -
      - B/Cb/V min [7:0]
    * - 12
      - :cspan:`4` R/Cr/H sum [31:0]
    * - 16
      - :cspan:`4` G/Y/S sum [31:0]
    * - 20
      - :cspan:`4` B/Cb/V sum [31:0]
    * - 24
      - :cspan:`4` R/Cr/H bin 0 [31:0]
    * -
      - :cspan:`4` ...
    * - 276
      - :cspan:`4` R/Cr/H bin 63 [31:0]
    * - 280
      - :cspan:`4` G/Y/S bin 0 [31:0]
    * -
      - :cspan:`4` ...
    * - 532
      - :cspan:`4` G/Y/S bin 63 [31:0]
    * - 536
      - :cspan:`4` B/Cb/V bin 0 [31:0]
    * -
      - :cspan:`4` ...
    * - 788
      - :cspan:`4` B/Cb/V bin 63 [31:0]

.. flat-table:: VSP1 HGO Data - 64 Bins, Max Mode (264 bytes)
    :header-rows:  2
    :stub-columns: 0

    * - Offset
      - :cspan:`4` Memory
    * -
      - [31:24]
      - [23:16]
      - [15:8]
      - [7:0]
    * - 0
      -
      - max(R,G,B) max [7:0]
      -
      - max(R,G,B) min [7:0]
    * - 4
      - :cspan:`4` max(R,G,B) sum [31:0]
    * - 8
      - :cspan:`4` max(R,G,B) bin 0 [31:0]
    * -
      - :cspan:`4` ...
    * - 260
      - :cspan:`4` max(R,G,B) bin 63 [31:0]

.. flat-table:: VSP1 HGO Data - 256 Bins, Normal Mode (1032 bytes)
    :header-rows:  2
    :stub-columns: 0

    * - Offset
      - :cspan:`4` Memory
    * -
      - [31:24]
      - [23:16]
      - [15:8]
      - [7:0]
    * - 0
      -
      - Y max [7:0]
      -
      - Y min [7:0]
    * - 4
      - :cspan:`4` Y sum [31:0]
    * - 8
      - :cspan:`4` Y bin 0 [31:0]
    * -
      - :cspan:`4` ...
    * - 1028
      - :cspan:`4` Y bin 255 [31:0]

.. flat-table:: VSP1 HGO Data - 256 Bins, Max Mode (1032 bytes)
    :header-rows:  2
    :stub-columns: 0

    * - Offset
      - :cspan:`4` Memory
    * -
      - [31:24]
      - [23:16]
      - [15:8]
      - [7:0]
    * - 0
      -
      - max(R,G,B) max [7:0]
      -
      - max(R,G,B) min [7:0]
    * - 4
      - :cspan:`4` max(R,G,B) sum [31:0]
    * - 8
      - :cspan:`4` max(R,G,B) bin 0 [31:0]
    * -
      - :cspan:`4` ...
    * - 1028
      - :cspan:`4` max(R,G,B) bin 255 [31:0]