Hi, Hans.
On 09/24/2012 11:46 AM, Hans de Goede wrote:
Hi,
On 09/24/2012 07:17 PM, Chris MacGregor wrote:
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.
Ok, sofar I'm following you, but are you saying that the correction
you need to apply for the green pixels on the same row as red pixels,
is different then the one for the green pixels on the same row as blue
pixels ?
IIRC, when we were calibrating, the two greens were at some times
different. The gain settings we're using at the moment are in fact the
same for both greens - we had to compromise to avoid getting into higher
values that increase the noise more than we like - but I don't know that
it would be that way in the future.
I can understand that the green "lenses" let through a different
amount of infrared light then sat the red lenses, but is there any
(significant) differences between the green lenses on 2 different rows?
I don't have time right now to dig out the datasheet and re-read it, but
IIRC the auto-BLC (for instance) is row-wise, and consequently the
greens could actually need slightly different values. I think the
datasheet made it fairly clear that the motivation for including
separate green controls was because you might need them in practice, not
because the hardware guys were punting the problem over to the software
side.
(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?
Well if these are showing up in something like a user oriented
control-panel (which they may) then having one slider for both
certainly is more userfriendly.
Okay, that's a fair point. But an application that wanted to could
insulate the user from it fairly easily.
I'm not opposed to having a single control, *if* there is some way for
apps to control the greens separately when they need to. I don't have a
brilliant solution for this offhand, other than just exposing the
separate controls.
Regards,
Hans
Thanks,
Chris
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