Hi Nicolas,
On Mon, Nov 02, 2020 at 03:39:25PM -0500, Nicolas Dufresne wrote:
> Le dimanche 01 novembre 2020 à 02:38 +0200, Laurent Pinchart a écrit :
> > On Thu, Sep 24, 2020 at 02:24:44PM -0400, Nicolas Dufresne wrote:
> > > Le mercredi 23 septembre 2020 à 05:43 +0300, Laurent Pinchart a écrit :
> > > > Add three new formats storing packed YUV 4:4:4 in 10-, 12- and 16-bpc
> > > > variants, with component order VUY. They are used by the Xilinx Video
> > > > Frame Buffer Read/Write IP cores.
> > > >
> > > > Signed-off-by: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx>
> > > > ---
> > > > .../media/v4l/pixfmt-packed-yuv.rst | 55 +++++++++++++++++++
> > > > include/uapi/linux/videodev2.h | 3 +
> > > > 2 files changed, 58 insertions(+)
> > > >
> > > > diff --git a/Documentation/userspace-api/media/v4l/pixfmt-packed-yuv.rst b/Documentation/userspace-api/media/v4l/pixfmt-packed-yuv.rst
> > > > index 3c7c8e38b7b7..4753ee8c6b7d 100644
> > > > --- a/Documentation/userspace-api/media/v4l/pixfmt-packed-yuv.rst
> > > > +++ b/Documentation/userspace-api/media/v4l/pixfmt-packed-yuv.rst
> > > > @@ -264,6 +264,61 @@ the second byte and Y'\ :sub:`7-0` in the third byte.
> > > > applications and drivers.
> > > >
> > > > +The next table lists the packed YUV 4:4:4 formats with more than 8 bits per
> > > > +component. They are named similarly to the formats with less than 8 bits per
> > > > +components, based on the order of the Y, Cb and Cr components as seen in a
> > > > +word, which is then stored in memory in little endian byte order, and on the
> > > > +number of bits for each component.
> > > > +
> > > > +.. flat-table:: Packed YUV Image Formats (more than 8bpc)
> > > > + :header-rows: 1
> > > > + :stub-columns: 0
> > > > +
> > > > + * - Identifier
> > > > + - Code
> > > > + - Byte 0
> > > > + - Byte 1
> > > > + - Byte 2
> > > > + - Byte 3
> > > > + - Byte 4
> > > > + - Byte 5
> > > > +
> > > > + * .. _V4L2-PIX-FMT-XVUY2101010:
> > > > +
> > > > + - ``V4L2_PIX_FMT_XVUY2101010``
> > > > + - 'VY30'
> > > > +
> > > > + - Y'\ :sub:`7-0`
> > > > + - Cb\ :sub:`5-0` Y'\ :sub:`9-8`
> > > > + - Cr\ :sub:`3-0` Cb\ :sub:`9-6`
> > > > + - `-`\ :sub:`1-0` Cr\ :sub:`9-4`
> > > > + -
> > > > +
> > > > + * .. _V4L2-PIX-FMT-XVUY4121212:
> > > > +
> > > > + - ``V4L2_PIX_FMT_XVUY4121212``
> > > > + - 'VY36'
> > > > +
> > > > + - Y'\ :sub:`7-0`
> > > > + - Cb\ :sub:`3-0` Y'\ :sub:`11-8`
> > > > + - Cb\ :sub:`11-4`
> > > > + - Cr\ :sub:`7-0`
> > > > + - `-`\ :sub:`3-0` Cr\ :sub:`11-8`
> > > > + -
> > > > +
> > > > + * .. _V4L2-PIX-FMT-VUY161616:
> > > > +
> > > > + - ``V4L2_PIX_FMT_VUY161616``
> > > > + - 'VY40'
> > > > +
> > > > + - Y'\ :sub:`7-0`
> > > > + - Y'\ :sub:`15-8`
> > > > + - Cb\ :sub:`7-0`
> > > > + - Cb\ :sub:`15-8`
> > > > + - Cr\ :sub:`7-0`
> > > > + - Cr\ :sub:`15-8`
> > > > +
> > > > +
> > > > 4:2:2 Subsampling
> > > > =================
> > > >
> > > >
> > > >
> > > >
> > > > diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h
> > > > index 503a938ea98c..9b4cab651df7 100644
> > > > --- a/include/uapi/linux/videodev2.h
> > > > +++ b/include/uapi/linux/videodev2.h
> > > > @@ -605,6 +605,9 @@ struct v4l2_pix_format {
> > > > #define V4L2_PIX_FMT_YUVA32 v4l2_fourcc('Y', 'U', 'V', 'A') /* 32 YUVA-8-8-8-8 */
> > > > #define V4L2_PIX_FMT_YUVX32 v4l2_fourcc('Y', 'U', 'V', 'X') /* 32 YUVX-8-8-8-8 */
> > > > #define V4L2_PIX_FMT_M420 v4l2_fourcc('M', '4', '2', '0') /* 12 YUV 4:2:0 2 lines y, 1 line uv interleaved */
> > > > +#define V4L2_PIX_FMT_XVUY2101010 v4l2_fourcc('V', 'Y', '3', '0') /* 32 XVUY-2-10-10-10 */
> > > > +#define V4L2_PIX_FMT_XVUY4121212 v4l2_fourcc('V', 'Y', '3', '6') /* 40 XVUY-4-12-12-12 */
> > > > +#define V4L2_PIX_FMT_VUY161616 v4l2_fourcc('V', 'Y', '4', '8') /* 48 VUY-16-16-16 */
> > >
> > > That is very hard to read. I'm fine with being more verbose, but I
> > > think it would be nice if it remains human readable. A possible fix
> > > could be:
> > >
> > > V4L2_PIX_FMT_XVUY_2_10_10_10
> >
> > Hans has proposed an interleave naming scheme in the review of 13/16.
> > This would become X2V10U10Y10. He also mentioned an alternative option
> > that would match your proposal above. I don't have a strong preference.
> > Can you and Hans agree on the best option ?
>
> Not that I have a strong preference, they equally describe the format.
>
> 1. V4L2_PIX_FMT_X2V10U10Y10:
>
> This is more compact and more likely to fit 80 to 100 chars when
> coding.
>
> 2. V4L2_PIX_FMT_XVUY_2_10_10_10:
>
> It splits the component order and leave the component size easy to
> read. It is overall easier to identify on first read.
>
> I read more code then I write, so my obvious preference would be 2.,
> but I'm fine with any.
I had already updated the patches with the first option, so I'll send a
v2 with that, while waiting for Hans to comment on his preference. If he
doesn't mind much either way, I'll update to the second option and send
a v3.
> > > Another approach is a bit-per-component and pixel size approach. That
> > > one would be XYUV10_32. It is more cryptic, and you need more doc to
> > > understand.
> > >
> > > That brings me to endianness, I believe it does matter for these
> > > unaligned component, so that should be documented (little).
> >
> > That's already documented in
> > Documentation/userspace-api/media/v4l/pixfmt-packed-yuv.rst.
>
> Ack.
>
> > > > /* two planes -- one Y, one Cr + Cb interleaved */
> > > > #define V4L2_PIX_FMT_NV12 v4l2_fourcc('N', 'V', '1', '2') /* 12 Y/CbCr 4:2:0 */
--
Regards,
Laurent Pinchart
