Hi Hans, On Monday 24 September 2012 12:55:53 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 > > 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 ? > > 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 ... I've never had to set different gains for the two green components either, although I haven't done much with them. > > 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 ... Some might at least. > 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. The offset is usually applied after the gain, so you might need different offsets to compensate for a fixed error that is multiplied by different gains. > 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, 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
