On 09/24/2012 07:42 AM, Prabhakar Lad wrote:
Hi Hans,
On Mon, Sep 24, 2012 at 4:25 PM, Hans de Goede <hdegoede@xxxxxxxxxx> wrote:
Hi,
On 09/23/2012 01:26 PM, Prabhakar Lad wrote:
Hi All,
The CCD/Sensors have the capability to adjust the R/ye, Gr/Cy, Gb/G,
B/Mg gain values.
Since these control can be re-usable I am planning to add the
following gain controls as part
of the framework:
1: V4L2_CID_GAIN_RED
2: V4L2_CID_GAIN_GREEN_RED
3: V4L2_CID_GAIN_GREEN_BLUE
Not all sensors have separate V4L2_CID_GAIN_GREEN_RED /
V4L2_CID_GAIN_GREEN_BLUE,
so we will need a separate control for sensors which have one combined gain
called simply V4L2_CID_GAIN_GREEN
Agreed
Also do we really need separate V4L2_CID_GAIN_GREEN_RED /
V4L2_CID_GAIN_GREEN_BLUE
controls? I know hardware has them, but in my experience that is only done
as it
is simpler to make the hardware this way (fully symmetric sensor grid), have
you ever
tried actually using different gain settings for the 2 different green rows
?
Never tried it.
I've and that always results in an ugly checker board pattern. So I think we
can
and should only have a V4L2_CID_GAIN_GREEN, and for sensors with 2 green
gains
have that control both, forcing both to always have the same setting, which
is
really what you want anyways ...
Agreed.
Please don't do this. I am working with the MT9P031, which has separate
gains, and as we are using the color version of the sensor (which we can
get much more cheaply) with infrared illumination, we correct for the
slightly different response levels of the different color channels by
adjusting the individual gain controls. (I have patches to add the
controls, but I haven't had time yet to get them into good enough shape
to submit - sorry!)
It seems to me that for applications that want to set them to the same
value (presumably the vast majority), it is not so hard to set both the
green_red and green_blue. If you implement a single control, what
happens for the (admittedly rare) application that needs to control them
separately?
Regards,
--Prabhakar Lad
4: V4L2_CID_GAIN_BLUE
5: V4L2_CID_GAIN_OFFSET
GAIN_OFFSET that sounds a bit weird... GAIN_OFFSET sounds like it is
a number which gets added to the 3/4 gain settings before the gain gets
applied,
but I assume that you just mean a number which gets added to the value from
the pixel, either before or after the gain is applied and I must admit I
cannot
come up with a better name.
I believe (not sure) that some sensors have these per color ... The question
is if it makes sense to actually control this per color though, I don't
think it
does as it is meant to compensate for any fixed measuring errors, which are
the
same for all 3/4 colors. Note that all the sensor cells are exactly the
same,
later on a color grid gets added on top of the sensors to turn them into
r/g/b
cells, but physically they are the same cells, so with the same process and
temperature caused measuring errors...
Regards,
Hans
--
To unsubscribe from this list: send the line "unsubscribe linux-media" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
--
To unsubscribe from this list: send the line "unsubscribe linux-media" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
