Hi Naush
On Wed, Mar 06, 2024 at 12:53:03PM +0000, Naushir Patuck wrote:
> Hi Jacopo,
>
> Thank you for your patch.
>
> On Tue, 5 Mar 2024 at 16:09, 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>
> > ---
> > .../userspace-api/media/v4l/pixfmt-bayer.rst | 1 +
> > .../media/v4l/pixfmt-pisp-comp-rggb.rst | 70 +++++++++++++++++++
> > drivers/media/v4l2-core/v4l2-ioctl.c | 10 +++
> > include/uapi/linux/videodev2.h | 12 ++++
> > 4 files changed, 93 insertions(+)
> > create mode 100644 Documentation/userspace-api/media/v4l/pixfmt-pisp-comp-rggb.rst
>
> Does the filename need to have the Bayer order suffix (rggb in this
> case), or would it be better to name it pixfmt-pisp-comp?
>
The other RAW formats file names have an 'srggb' suffix but I guess the
relevant part there is the bit-depth and any eventual compression
Documentation/userspace-api/media/v4l/pixfmt-srggb10alaw8.rst
Documentation/userspace-api/media/v4l/pixfmt-srggb10dpcm8.rst
Documentation/userspace-api/media/v4l/pixfmt-srggb10-ipu3.rst
Documentation/userspace-api/media/v4l/pixfmt-srggb10p.rst
Documentation/userspace-api/media/v4l/pixfmt-srggb10.rst
Documentation/userspace-api/media/v4l/pixfmt-srggb12p.rst
I would say the correct name would probably be then
srggb-pisp-comp.rst
as it denotes it's a raw format. Being it an 8-bit format we could
even go do 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..81b69ea4084a 100644
> > --- a/Documentation/userspace-api/media/v4l/pixfmt-bayer.rst
> > +++ b/Documentation/userspace-api/media/v4l/pixfmt-bayer.rst
> > @@ -30,3 +30,4 @@ orders. See also `the Wikipedia article on Bayer filter
> > pixfmt-srggb14
> > pixfmt-srggb14p
> > pixfmt-srggb16
> > + pixfmt-pisp-comp-rggb
'p' comes before 's'
One day I'll learn the alphabet
> > diff --git a/Documentation/userspace-api/media/v4l/pixfmt-pisp-comp-rggb.rst b/Documentation/userspace-api/media/v4l/pixfmt-pisp-comp-rggb.rst
> > new file mode 100644
> > index 000000000000..7be1b25b2241
> > --- /dev/null
> > +++ b/Documentation/userspace-api/media/v4l/pixfmt-pisp-comp-rggb.rst
> > @@ -0,0 +1,70 @@
> > +.. 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:
> > +
> > +================================================
> > +Raspberry Pi PiSP compressed 8-bit Bayer formats
> > +================================================
> > +
> > +Description
> > +===========
> > +
> > +Raspberry Pi ISP uses a family of three fixed-rate compressed Bayer formats.
>
> s/Raspberry Pi ISP/The Raspberry Pi ISP (PiSP)/
>
> These very minor comments aside:
> Reviewed-by: Naushir Patuck <naush@xxxxxxxxxxxxxxx>
>
> > +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).
> > +
> > +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 18e9aa1297e1..fc7af7337ab4 100644
> > --- a/drivers/media/v4l2-core/v4l2-ioctl.c
> > +++ b/drivers/media/v4l2-core/v4l2-ioctl.c
> > @@ -1516,6 +1516,16 @@ 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 c3daf61f43d5..feab8a153d2e 100644
> > --- a/include/uapi/linux/videodev2.h
> > +++ b/include/uapi/linux/videodev2.h
> > @@ -818,6 +818,18 @@ 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 */
> > --
> > 2.43.2
> >
