Hi Laurent,
On Wed, Dec 21, 2011 at 11:23:26PM +0100, Laurent Pinchart wrote:
> Hi Manju,
>
> On Wednesday 21 December 2011 14:56:36 Hadli, Manjunath wrote:
> > On Wed, Dec 21, 2011 at 05:32:08, Laurent Pinchart wrote:
> > > On Friday 16 December 2011 14:42:48 Hadli, Manjunath wrote:
> > > > On Thu, Dec 15, 2011 at 18:30:47, Laurent Pinchart wrote:
> > > > > On Thursday 15 December 2011 13:24:58 Manjunath Hadli wrote:
> > > > > > add new macro V4L2_PIX_FMT_SGRBG10ALAW8 to represent Bayer format
> > > > > > frames compressed by A-LAW alogorithm.
> > > > > > add V4L2_PIX_FMT_UV8 to represent storage of C (UV interleved)
> > > > > > only.
> > > > > >
> > > > > > Signed-off-by: Manjunath Hadli <manjunath.hadli@xxxxxx>
> > > > > > Cc: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx>
> > > > > > ---
> > > > > >
> > > > > > include/linux/videodev2.h | 6 ++++++
> > > > > > 1 files changed, 6 insertions(+), 0 deletions(-)
> > > > >
> > > > > Could you please also document these formats in
> > > > > Documentation/DocBook/media/v4l ?
> > > >
> > > > I will. Sorry to have missed that out.
> > > >
> > > > > > diff --git a/include/linux/videodev2.h b/include/linux/videodev2.h
> > > > > > index 4b752d5..969112d 100644
> > > > > > --- a/include/linux/videodev2.h
> > > > > > +++ b/include/linux/videodev2.h
> > > > > > @@ -338,6 +338,9 @@ struct v4l2_pix_format {
> > > > > >
> > > > > > #define V4L2_PIX_FMT_HM12 v4l2_fourcc('H', 'M', '1', '2') /* 8
> > > > > > YUV
> > > > > >
> > > > > > 4:2:0 16x16 macroblocks */ #define V4L2_PIX_FMT_M420
> > > > > > v4l2_fourcc('M', '4', '2', '0') /* 12 YUV 4:2:0 2 lines y, 1 line
> > > > > > uv interleaved */
> > > > > >
> > > > > > +/* Chrominance formats */
> > > > > > +#define V4L2_PIX_FMT_UV8 v4l2_fourcc('U', 'V', '8', ' ') /*
> > > > > > 8 UV 4:4 */ +
> > > > > >
> > > > > > /* 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 */ #define V4L2_PIX_FMT_NV21 v4l2_fourcc('N', 'V', '2',
> > > > > > '1') /* 12 Y/CrCb 4:2:0 */ @@ -366,6 +369,9 @@ struct
> > > > > > v4l2_pix_format { #define V4L2_PIX_FMT_SRGGB12 v4l2_fourcc('R',
> > > > > > 'G', '1', '2') /* 12 RGRG.. GBGB.. */ /* 10bit raw bayer DPCM
> > > > > > compressed to 8 bits */ #define V4L2_PIX_FMT_SGRBG10DPCM8
> > > > > > v4l2_fourcc('B', 'D', '1', '0')
> > > > > > + /* 10bit raw bayer a-law compressed to 8 bits */ #define
> > > > > > +V4L2_PIX_FMT_SGRBG10ALAW8 v4l2_fourcc('A', 'L', 'W', '8')
> > > > > > +
> > > > >
> > > > > That's not very future-proof, how would you describe SGBRG10ALAW8
> > > > > for instance ?
> > > > >
> > > > > Maybe it's time to standardize FOURCCs for Bayer new formats. We
> > > > > have 4 characters, we could start with 'B' to denote Bayer, followed
> > > > > by one character for the order, one for the compression, and one for
> > > > > the number of bits.
> > > >
> > > > I agree.
> > > > May be ('B', 'G', 'A', '8') is fine for the above?
> > >
> > > We need to describe at last BGGR, GBRG, GRBG and RGGB. We could use 'B',
> > > 'g', 'G' and 'R' respectively for the second character. The third
> > > character would be 'A' for A-law and 'D' for DPCM, and the fourth
> > > character could describe the bus width in bits from 0 to 15 with '0' -
> > > '9', 'A' - 'F'. However, I suspect that we will need 16-bit wide busses
> > > for raw Bayer at some point, and a 0 width is definitely not useful. We
> > > could thus offset the width by some value.
> > >
> > > This is just a preliminary idea, I'm open to suggestions.
> >
> > I think it is a very good suggestion that we can go with.
> > B : BGGR
> > g : GBRG
> > G : GRBG
> > R : RGGB
> >
> > and 0-F can signify 1-16.
>
> Hans, Guennadi, Sakari, any opinion on that as well ?
I think four letters simply aren't enough to universally describe a media
bus format in a human-readable way. We can aim to that, but we will have to
make compromises.
For example, DPCM compressed format has two important parameters beyond
pixel order and the colour space, the uncompressed depth and the compressed
depth. Typically one doesn't compress the data too much, but things like
10-to-6 bits are well possible.
Could we use a single letter to tell that a format is both bayer and DPCM
compressed? I'd go for 'b'. Raw bayer alaw could be denoted by 'a'.
Then raw bayer, GBRG pixel order 10-to-7 bits would be called "bgA7". The
same in Alaw would be "agA7".
What do you think?
--
Sakari Ailus
e-mail: sakari.ailus@xxxxxx jabber/XMPP/Gmail: sailus@xxxxxxxxxxxxxx
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