On Monday 24 September 2012 12:16:01 Chris MacGregor wrote: > On 09/24/2012 11:46 AM, Hans de Goede wrote: > > On 09/24/2012 07:17 PM, Chris MacGregor wrote: > >> On 09/24/2012 07:42 AM, Prabhakar Lad wrote: > >>> On Mon, Sep 24, 2012 at 4:25 PM, Hans de Goede wrote: > >>>> 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. Those gains are low-level controls, they will very likely not appear in a generic panel. > 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. As you have a use case for separate controls I'd vote for having separate controls. -- Regards, Laurent Pinchart -- 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
