Hi Sakari,
Thanks for a review! I'll fix all the cosmetic issues, thanks. As for
other comments:
On Wed, 13 Jan 2016, Sakari Ailus wrote:
[snip]
> > --- /dev/null
> > +++ b/Documentation/DocBook/media/v4l/pixfmt-y12i.xml
> > @@ -0,0 +1,49 @@
> > +<refentry id="V4L2-PIX-FMT-Y12I">
> > + <refmeta>
> > + <refentrytitle>V4L2_PIX_FMT_Y12I ('Y12I ')</refentrytitle>
>
> Extra space after 4cc. ^
>
> > + &manvol;
> > + </refmeta>
> > + <refnamediv>
> > + <refname><constant>V4L2_PIX_FMT_Y12I</constant></refname>
> > + <refpurpose>Interleaved grey-scale image, e.g. from a stereo-pair</refpurpose>
> > + </refnamediv>
> > + <refsect1>
> > + <title>Description</title>
> > +
> > + <para>This is a grey-scale image with a depth of 12 bits per pixel, but with
> > +pixels from 2 sources interleaved and bit-packed. Each pixel is stored in a
> > +24-bit word. E.g. data, stored by a R200 RealSense camera on a little-endian
> > +machine can be deinterlaced using</para>
>
> I think we should precisely define the format, either big or little. Is the
> endianness of the format affected by the machine endianness? (I'd guess no,
> but that's just a guess.)
Ok, since this works on a LE machine:
left0 = 0xfff & *(__u16 *)buf;
I think we can call data LE in the buffer. But specifying left-right order
cannot be done in terms of endianness, so, I provided that code snippet.
> I wonder if the format should convey the information which one is right and
> which one is left, e.g. by adding "LR" to the name.
You mean to distinguish between LR and RL? Can do in principle, yes.
> No need to mention RealSense specifically IMO.
Ok.
> > +
> > +<para>
> > +<programlisting>
> > +__u8 *buf;
> > +left0 = 0xfff & *(__u16 *)buf;
> > +rirhgt0 = *(__u16 *)(buf + 1) >> 4;
>
> "right"
[snip]
> > diff --git a/Documentation/DocBook/media/v4l/pixfmt-z16.xml b/Documentation/DocBook/media/v4l/pixfmt-z16.xml
> > new file mode 100644
> > index 0000000..fac3c68
> > --- /dev/null
> > +++ b/Documentation/DocBook/media/v4l/pixfmt-z16.xml
> > @@ -0,0 +1,79 @@
> > +<refentry id="V4L2-PIX-FMT-Z16">
> > + <refmeta>
> > + <refentrytitle>V4L2_PIX_FMT_Z16 ('Z16 ')</refentrytitle>
> > + &manvol;
> > + </refmeta>
> > + <refnamediv>
> > + <refname><constant>V4L2_PIX_FMT_Z16</constant></refname>
> > + <refpurpose>Interleaved grey-scale image, e.g. from a stereo-pair</refpurpose>
> > + </refnamediv>
> > + <refsect1>
> > + <title>Description</title>
> > +
> > + <para>This is a 16-bit format, representing depth data. Each pixel is a
> > +distance in mm to the respective point in the image coordinates. Each pixel is
> > +stored in a 16-bit word in the little endian byte order.</para>
>
> The format itself looks quite generic but the unit might be specific to the
> device. It'd sound silly to add a new format if just the unit is different.
My understanding is, that each format must have a fixed meaning, i.e. a
fixed depth unit too, although it would definitely help to be able to
relax that requirement in this case.
> How about re-purpose the colourspace field for depth formats and
> add a flag telling the colour space field contains the unit and the unit
> prefix.
Hmmm... Not sure I find this a proper use of the .colorspace field...
> Not something to have in this patch nor patchset though: controls
> should gain that as well.
Sorry, didn't get this - how can a control tell you what units a specific
format uses? What if your camera can output depth in multiple units?
Thanks
Guennadi
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