Hi Nick
On Wed, May 29, 2024 at 10:39:40AM GMT, Nick Hollinghurst wrote:
> Hi all,
>
> I have just spotted an error here (the error is mine - sorry).
No problem, thanks for checking
>
> On Tue, 28 May 2024 at 17:04, Jacopo Mondi
> <jacopo.mondi@xxxxxxxxxxxxxxxx> wrote:
> >
> > Add Raspberry Pi compressed RAW Bayer formats.
> >
> > The compression algorithm description is provided by Nick Hollinghurst
> > <nick.hollinghurst@xxxxxxxxxxxxxxx> from Raspberry Pi.
> >
> > Signed-off-by: Jacopo Mondi <jacopo.mondi@xxxxxxxxxxxxxxxx>
> > Reviewed-by: Naushir Patuck <naush@xxxxxxxxxxxxxxx>
> > ---
> > .../userspace-api/media/v4l/pixfmt-bayer.rst | 1 +
> > .../media/v4l/pixfmt-srggb8-pisp-comp.rst | 74 +++++++++++++++++++
> > drivers/media/v4l2-core/v4l2-ioctl.c | 10 +++
> > include/uapi/linux/videodev2.h | 12 +++
> > 4 files changed, 97 insertions(+)
> > create mode 100644 Documentation/userspace-api/media/v4l/pixfmt-srggb8-pisp-comp.rst
> >
> > diff --git a/Documentation/userspace-api/media/v4l/pixfmt-bayer.rst b/Documentation/userspace-api/media/v4l/pixfmt-bayer.rst
> > index 2500413e5f43..ed3eb432967d 100644
> > --- a/Documentation/userspace-api/media/v4l/pixfmt-bayer.rst
> > +++ b/Documentation/userspace-api/media/v4l/pixfmt-bayer.rst
> > @@ -20,6 +20,7 @@ orders. See also `the Wikipedia article on Bayer filter
> > :maxdepth: 1
> >
> > pixfmt-srggb8
> > + pixfmt-srggb8-pisp-comp
> > pixfmt-srggb10
> > pixfmt-srggb10p
> > pixfmt-srggb10alaw8
> > diff --git a/Documentation/userspace-api/media/v4l/pixfmt-srggb8-pisp-comp.rst b/Documentation/userspace-api/media/v4l/pixfmt-srggb8-pisp-comp.rst
> > new file mode 100644
> > index 000000000000..ff0fbcf34258
> > --- /dev/null
> > +++ b/Documentation/userspace-api/media/v4l/pixfmt-srggb8-pisp-comp.rst
> > @@ -0,0 +1,74 @@
> > +.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
> > +
> > +.. _v4l2-pix-fmt-pisp-comp1-rggb:
> > +.. _v4l2-pix-fmt-pisp-comp1-grbg:
> > +.. _v4l2-pix-fmt-pisp-comp1-gbrg:
> > +.. _v4l2-pix-fmt-pisp-comp1-bggr:
> > +.. _v4l2-pix-fmt-pisp-comp1-mono:
> > +.. _v4l2-pix-fmt-pisp-comp2-rggb:
> > +.. _v4l2-pix-fmt-pisp-comp2-grbg:
> > +.. _v4l2-pix-fmt-pisp-comp2-gbrg:
> > +.. _v4l2-pix-fmt-pisp-comp2-bggr:
> > +.. _v4l2-pix-fmt-pisp-comp2-mono:
> > +
> > +**************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************
> > +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')
> > +**************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************
> > +
> > +================================================
> > +Raspberry Pi PiSP compressed 8-bit Bayer formats
> > +================================================
> > +
> > +Description
> > +===========
> > +
> > +The Raspberry Pi ISP (PiSP) uses a family of three fixed-rate compressed Bayer
> > +formats. A black-level offset may be subtracted to improve compression
> > +efficiency; the nominal black level and amount of offset must be signalled out
> > +of band. Each scanline is padded to a multiple of 8 pixels wide, and each block
> > +of 8 horizontally-contiguous pixels is coded using 8 bytes.
> > +
> > +Mode 1 uses a quantization and delta-based coding scheme which preserves up to
> > +12 significant bits. Mode 2 is a simple sqrt-like companding scheme with 6 PWL
> > +chords, preserving up to 12 significant bits. Mode 3 combines both companding
> > +(with 4 chords) and the delta scheme, preserving up to 14 significant bits.
> > +
> > +The remainder of this description applies to Modes 1 and 3.
> > +
> > +Each block of 8 pixels is separated into even and odd phases of 4 pixels,
> > +coded independently by 32-bit words at successive locations in memory.
> > +The two LS bits of each 32-bit word give its "quantization mode".
> > +
> > +In quantization mode 0, the lowest 321 quantization levels are multiples of
> > +FSD/4096 and the remaining levels are successive multiples of FSD/2048.
> > +Quantization modes 1 and 2 use linear quantization with step sizes of
> > +FSD/1024 and FSD/512 respectively. Each of the four pixels is quantized
> > +independently, with rounding to the nearest level.
> > +In quantization mode 2 where the middle two samples have quantized values
> > +(q1,q2) both in the range [384..511], they are coded using 9 bits for q1
> > +followed by 7 bits for (q2 & 127). Otherwise, for quantization modes
> > +0, 1 and 2: a 9-bit field encodes MIN(q1,q2) which must be in the range
> > +[0..511] and a 7-bit field encodes (q2-q1+64) which must be in [0..127].
> > +
> > +Each of the outer samples (q0,q3) is encoded using a 7-bit field based
> > +on its inner neighbour q1 or q2. In quantization mode 2 where the inner
> > +sample has a quantized value in the range [448..511], the field value is
> > +(q0-384). Otherwise for quantization modes 0, 1 and 2: The outer sample
> > +is encoded as (q0-MAX(0,q1-64)). q3 is likewise coded based on q2.
> > +Each of these values must be in the range [0..127]. All these fields
> > +of 2, 9, 7, 7, 7 bits respectively are packed in little-endian order
> > +to give a 32-bit word with LE byte order.
> > +
> > +Quantization mode 3 has a "7.5-bit" escape, used when none of the above
> > +encodings will fit. Each pixel value is quantized to the nearest of 176
> > +levels, where the lowest 48 levels are multiples of FSD/256 and the
> > +remaining levels are multiples of FSD/512 (level 175 represents values
> > +very close to FSD and may require saturating arithmetic to decode).
>
> Here I must have confused the step size with the fraction, writing FSD/512
> when I meant FSD/128. I also managed to mix up a constant used in the
> encoder (47+1) with a number of steps (94+1).
> What I should have written is:
>
> +levels, where the lowest 95 levels are multiples of FSD/256 and the
> +remaining levels are multiples of FSD/128 (level 175 represents values
> +very close to FSD and may require saturating arithmetic to decode).
Thanks, I'll take this in in v9
>
> Nick
>
>
> > +
> > +Each pair of quantized pixels (q0,q1) or (q2,q3) is jointly coded
> > +by a 15-bit field: 2816*(q0>>4) + 16*q1 + (q0&15).
> > +Three fields of 2, 15, 15 bits are packed in LE order {15,15,2}.
> > +
> > +An implementation of a software decoder of compressed formats is available
> > +in `Raspberry Pi camera applications code base
> > +<https://github.com/raspberrypi/rpicam-apps/blob/main/image/dng.cpp>`_.
> > diff --git a/drivers/media/v4l2-core/v4l2-ioctl.c b/drivers/media/v4l2-core/v4l2-ioctl.c
> > index 7c684788997c..5eb4d797d259 100644
> > --- a/drivers/media/v4l2-core/v4l2-ioctl.c
> > +++ b/drivers/media/v4l2-core/v4l2-ioctl.c
> > @@ -1532,6 +1532,16 @@ static void v4l_fill_fmtdesc(struct v4l2_fmtdesc *fmt)
> > case V4L2_PIX_FMT_MT2110T: descr = "Mediatek 10bit Tile Mode"; break;
> > case V4L2_PIX_FMT_MT2110R: descr = "Mediatek 10bit Raster Mode"; break;
> > case V4L2_PIX_FMT_HEXTILE: descr = "Hextile Compressed Format"; break;
> > + case V4L2_PIX_FMT_PISP_COMP1_RGGB: descr = "PiSP 8b RGRG/GBGB mode1 compr"; break;
> > + case V4L2_PIX_FMT_PISP_COMP1_GRBG: descr = "PiSP 8b GRGR/BGBG mode1 compr"; break;
> > + case V4L2_PIX_FMT_PISP_COMP1_GBRG: descr = "PiSP 8b GBGB/RGRG mode1 compr"; break;
> > + case V4L2_PIX_FMT_PISP_COMP1_BGGR: descr = "PiSP 8b BGBG/GRGR mode1 compr"; break;
> > + case V4L2_PIX_FMT_PISP_COMP1_MONO: descr = "PiSP 8b monochrome mode1 compr"; break;
> > + case V4L2_PIX_FMT_PISP_COMP2_RGGB: descr = "PiSP 8b RGRG/GBGB mode2 compr"; break;
> > + case V4L2_PIX_FMT_PISP_COMP2_GRBG: descr = "PiSP 8b GRGR/BGBG mode2 compr"; break;
> > + case V4L2_PIX_FMT_PISP_COMP2_GBRG: descr = "PiSP 8b GBGB/RGRG mode2 compr"; break;
> > + case V4L2_PIX_FMT_PISP_COMP2_BGGR: descr = "PiSP 8b BGBG/GRGR mode2 compr"; break;
> > + case V4L2_PIX_FMT_PISP_COMP2_MONO: descr = "PiSP 8b monochrome mode2 compr"; break;
> > default:
> > if (fmt->description[0])
> > return;
> > diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h
> > index 96fc0456081e..4e91362da6da 100644
> > --- a/include/uapi/linux/videodev2.h
> > +++ b/include/uapi/linux/videodev2.h
> > @@ -816,6 +816,18 @@ struct v4l2_pix_format {
> > #define V4L2_PIX_FMT_IPU3_SGRBG10 v4l2_fourcc('i', 'p', '3', 'G') /* IPU3 packed 10-bit GRBG bayer */
> > #define V4L2_PIX_FMT_IPU3_SRGGB10 v4l2_fourcc('i', 'p', '3', 'r') /* IPU3 packed 10-bit RGGB bayer */
> >
> > +/* Raspberry Pi PiSP compressed formats. */
> > +#define V4L2_PIX_FMT_PISP_COMP1_RGGB v4l2_fourcc('P', 'C', '1', 'R') /* PiSP 8-bit mode 1 compressed RGGB bayer */
> > +#define V4L2_PIX_FMT_PISP_COMP1_GRBG v4l2_fourcc('P', 'C', '1', 'G') /* PiSP 8-bit mode 1 compressed GRBG bayer */
> > +#define V4L2_PIX_FMT_PISP_COMP1_GBRG v4l2_fourcc('P', 'C', '1', 'g') /* PiSP 8-bit mode 1 compressed GBRG bayer */
> > +#define V4L2_PIX_FMT_PISP_COMP1_BGGR v4l2_fourcc('P', 'C', '1', 'B') /* PiSP 8-bit mode 1 compressed BGGR bayer */
> > +#define V4L2_PIX_FMT_PISP_COMP1_MONO v4l2_fourcc('P', 'C', '1', 'M') /* PiSP 8-bit mode 1 compressed monochrome */
> > +#define V4L2_PIX_FMT_PISP_COMP2_RGGB v4l2_fourcc('P', 'C', '2', 'R') /* PiSP 8-bit mode 2 compressed RGGB bayer */
> > +#define V4L2_PIX_FMT_PISP_COMP2_GRBG v4l2_fourcc('P', 'C', '2', 'G') /* PiSP 8-bit mode 2 compressed GRBG bayer */
> > +#define V4L2_PIX_FMT_PISP_COMP2_GBRG v4l2_fourcc('P', 'C', '2', 'g') /* PiSP 8-bit mode 2 compressed GBRG bayer */
> > +#define V4L2_PIX_FMT_PISP_COMP2_BGGR v4l2_fourcc('P', 'C', '2', 'B') /* PiSP 8-bit mode 2 compressed BGGR bayer */
> > +#define V4L2_PIX_FMT_PISP_COMP2_MONO v4l2_fourcc('P', 'C', '2', 'M') /* PiSP 8-bit mode 2 compressed monochrome */
> > +
> > /* SDR formats - used only for Software Defined Radio devices */
> > #define V4L2_SDR_FMT_CU8 v4l2_fourcc('C', 'U', '0', '8') /* IQ u8 */
> > #define V4L2_SDR_FMT_CU16LE v4l2_fourcc('C', 'U', '1', '6') /* IQ u16le */
> > --
> > 2.45.1
>
