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0171157d45
The patches were generated from the RPi repo with the following command: git format-patch v6.6.44..rpi-6.6.y Signed-off-by: Álvaro Fernández Rojas <noltari@gmail.com>
107 lines
5.8 KiB
Diff
107 lines
5.8 KiB
Diff
From 5d6318f242cce5f9b5677baedde736a2b81061df Mon Sep 17 00:00:00 2001
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From: Jacopo Mondi <jacopo.mondi@ideasonboard.com>
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Date: Wed, 17 Jan 2024 11:21:50 +0200
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Subject: [PATCH 1151/1215] media: uapi: Document PiSP Compressed RAW Bayer
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formats
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Document the Raspberry Pi compressed RAW Bayer formats.
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The compression algorithm description is provided by Nick Hollinghurst
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<nick.hollinghurst@raspberrypi.com> from Raspberry Pi.
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Signed-off-by: Jacopo Mondi <jacopo.mondi@ideasonboard.com>
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Reviewed-by: Naushir Patuck <naush@raspberrypi.com>
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---
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.../userspace-api/media/v4l/pixfmt-bayer.rst | 1 +
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.../media/v4l/pixfmt-srggb8-pisp-comp.rst | 74 +++++++++++++++++++
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2 files changed, 75 insertions(+)
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create mode 100644 Documentation/userspace-api/media/v4l/pixfmt-srggb8-pisp-comp.rst
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--- a/Documentation/userspace-api/media/v4l/pixfmt-bayer.rst
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+++ b/Documentation/userspace-api/media/v4l/pixfmt-bayer.rst
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@@ -20,6 +20,7 @@ orders. See also `the Wikipedia article
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:maxdepth: 1
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pixfmt-srggb8
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+ pixfmt-srggb8-pisp-comp
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pixfmt-srggb10
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pixfmt-srggb10p
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pixfmt-srggb10alaw8
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--- /dev/null
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+++ b/Documentation/userspace-api/media/v4l/pixfmt-srggb8-pisp-comp.rst
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@@ -0,0 +1,74 @@
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+.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
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+
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+.. _v4l2-pix-fmt-pisp-comp1-rggb:
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+.. _v4l2-pix-fmt-pisp-comp1-grbg:
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+.. _v4l2-pix-fmt-pisp-comp1-gbrg:
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+.. _v4l2-pix-fmt-pisp-comp1-bggr:
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+.. _v4l2-pix-fmt-pisp-comp1-mono:
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+.. _v4l2-pix-fmt-pisp-comp2-rggb:
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+.. _v4l2-pix-fmt-pisp-comp2-grbg:
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+.. _v4l2-pix-fmt-pisp-comp2-gbrg:
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+.. _v4l2-pix-fmt-pisp-comp2-bggr:
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+.. _v4l2-pix-fmt-pisp-comp2-mono:
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+
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+**************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************
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+V4L2_PIX_FMT_PISP_COMP1_RGGB ('PC1R'), V4L2_PIX_FMT_PISP_COMP1_GRBG ('PC1G'), V4L2_PIX_FMT_PISP_COMP1_GBRG ('PC1g'), V4L2_PIX_FMT_PISP_COMP1_BGGR ('PC1B), V4L2_PIX_FMT_PISP_COMP1_MONO ('PC1M'), V4L2_PIX_FMT_PISP_COMP2_RGGB ('PC2R'), V4L2_PIX_FMT_PISP_COMP2_GRBG ('PC2G'), V4L2_PIX_FMT_PISP_COMP2_GBRG ('PC2g'), V4L2_PIX_FMT_PISP_COMP2_BGGR ('PC2B), V4L2_PIX_FMT_PISP_COMP2_MONO ('PC2M')
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+**************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************
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+
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+================================================
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+Raspberry Pi PiSP compressed 8-bit Bayer formats
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+================================================
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+
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+Description
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+===========
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+
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+The Raspberry Pi ISP (PiSP) uses a family of three fixed-rate compressed Bayer
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+formats. A black-level offset may be subtracted to improve compression
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+efficiency; the nominal black level and amount of offset must be signalled out
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+of band. Each scanline is padded to a multiple of 8 pixels wide, and each block
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+of 8 horizontally-contiguous pixels is coded using 8 bytes.
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+
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+Mode 1 uses a quantization and delta-based coding scheme which preserves up to
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+12 significant bits. Mode 2 is a simple sqrt-like companding scheme with 6 PWL
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+chords, preserving up to 12 significant bits. Mode 3 combines both companding
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+(with 4 chords) and the delta scheme, preserving up to 14 significant bits.
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+
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+The remainder of this description applies to Modes 1 and 3.
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+
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+Each block of 8 pixels is separated into even and odd phases of 4 pixels,
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+coded independently by 32-bit words at successive locations in memory.
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+The two LS bits of each 32-bit word give its "quantization mode".
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+
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+In quantization mode 0, the lowest 321 quantization levels are multiples of
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+FSD/4096 and the remaining levels are successive multiples of FSD/2048.
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+Quantization modes 1 and 2 use linear quantization with step sizes of
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+FSD/1024 and FSD/512 respectively. Each of the four pixels is quantized
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+independently, with rounding to the nearest level.
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+In quantization mode 2 where the middle two samples have quantized values
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+(q1,q2) both in the range [384..511], they are coded using 9 bits for q1
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+followed by 7 bits for (q2 & 127). Otherwise, for quantization modes
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+0, 1 and 2: a 9-bit field encodes MIN(q1,q2) which must be in the range
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+[0..511] and a 7-bit field encodes (q2-q1+64) which must be in [0..127].
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+
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+Each of the outer samples (q0,q3) is encoded using a 7-bit field based
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+on its inner neighbour q1 or q2. In quantization mode 2 where the inner
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+sample has a quantized value in the range [448..511], the field value is
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+(q0-384). Otherwise for quantization modes 0, 1 and 2: The outer sample
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+is encoded as (q0-MAX(0,q1-64)). q3 is likewise coded based on q2.
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+Each of these values must be in the range [0..127]. All these fields
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+of 2, 9, 7, 7, 7 bits respectively are packed in little-endian order
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+to give a 32-bit word with LE byte order.
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+
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+Quantization mode 3 has a "7.5-bit" escape, used when none of the above
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+encodings will fit. Each pixel value is quantized to the nearest of 176
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+levels, where the lowest 95 levels are multiples of FSD/256 and the
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+remaining levels are multiples of FSD/128 (level 175 represents values
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+very close to FSD and may require saturating arithmetic to decode).
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+
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+Each pair of quantized pixels (q0,q1) or (q2,q3) is jointly coded
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+by a 15-bit field: 2816*(q0>>4) + 16*q1 + (q0&15).
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+Three fields of 2, 15, 15 bits are packed in LE order {15,15,2}.
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+
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+An implementation of a software decoder of compressed formats is available
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+in `Raspberry Pi camera applications code base
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+<https://github.com/raspberrypi/rpicam-apps/blob/main/image/dng.cpp>`_.
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