media/v4l/pixfmt-srggb8-pisp-comp.rst

1 .. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
3 .. _v4l2-pix-fmt-pisp-comp1-rggb:
4 .. _v4l2-pix-fmt-pisp-comp1-grbg:
5 .. _v4l2-pix-fmt-pisp-comp1-gbrg:
6 .. _v4l2-pix-fmt-pisp-comp1-bggr:
7 .. _v4l2-pix-fmt-pisp-comp1-mono:
8 .. _v4l2-pix-fmt-pisp-comp2-rggb:
9 .. _v4l2-pix-fmt-pisp-comp2-grbg:
10 .. _v4l2-pix-fmt-pisp-comp2-gbrg:
11 .. _v4l2-pix-fmt-pisp-comp2-bggr:
12 .. _v4l2-pix-fmt-pisp-comp2-mono:
19 Raspberry Pi PiSP compressed 8-bit Bayer formats
25 The Raspberry Pi ISP (PiSP) uses a family of three fixed-rate compressed Bayer
26 formats. A black-level offset may be subtracted to improve compression
29 of 8 horizontally-contiguous pixels is coded using 8 bytes.
31 Mode 1 uses a quantization and delta-based coding scheme which preserves up to
32 12 significant bits. Mode 2 is a simple sqrt-like companding scheme with 6 PWL
39 coded independently by 32-bit words at successive locations in memory.
40 The two LS bits of each 32-bit word give its "quantization mode".
44 Quantization modes 1 and 2 use linear quantization with step sizes of
50 0, 1 and 2: a 9-bit field encodes MIN(q1,q2) which must be in the range
51 [0..511] and a 7-bit field encodes (q2-q1+64) which must be in [0..127].
53 Each of the outer samples (q0,q3) is encoded using a 7-bit field based
56 (q0-384). Otherwise for quantization modes 0, 1 and 2: The outer sample
57 is encoded as (q0-MAX(0,q1-64)). q3 is likewise coded based on q2.
59 of 2, 9, 7, 7, 7 bits respectively are packed in little-endian order
60 to give a 32-bit word with LE byte order.
62 Quantization mode 3 has a "7.5-bit" escape, used when none of the above
69 by a 15-bit field: 2816*(q0>>4) + 16*q1 + (q0&15).
74 <https://github.com/raspberrypi/rpicam-apps/blob/main/image/dng.cpp>`_.