Hi Sakari, On 01/04/2012 10:24 PM, Sakari Ailus wrote: >>>>> I don't quite understand the purpose of the do_white_balance; the >>>>> automatic white balance algorithm is operational until it's disabled, >>>>> and after disabling it the white balance shouldn't change. What is the >>>>> extra functionality that the do_white_balance control implements? >>>> >>>> Maybe DO_WHITE_BALANCE was inspired by some hardware's behaviour, I don't >>>> know. I have nothing against this control. It allows you to perform >>>> one-shot white balance in a given moment in time. Simple and clear. >>> >>> Well, yes, if you have an automatic white balance algorithm which supports >>> "one-shot" mode. Typically it's rather a feedback loop. I guess this means >>> "just run one iteration". >>> >>> Something like this should possibly be used to get the white balance >>> correct by pointing the camera to an object of known colour (white >>> typically, I think). But this isn't it, at least based on the description >>> in the spec. >> >> Then either the spec is incorrect, or I'm mistaken. My understanding of the >> DO_WHITE_BALANCE control is exactly what you described. > > This is what the spec says: > > "This is an action control. When set (the value is ignored), the device will do > a white balance and then hold the current setting. Contrast this with the > boolean V4L2_CID_AUTO_WHITE_BALANCE, which, when activated, keeps adjusting the > white balance." > > I wonder if that should be then changed --- or is it just me who got a different > idea from the above description? Only you ? :-) Same as Laurent, I understood this control can be used to do white balance after pointing camera to a white object. Not sure if the description needs to be changed. > My understanding is that the operation for getting the white balance information > from a white object is by far simpler than getting the white balance correct > without that. > > These seem to be only two references to this control in drivers and both drivers > are grossly misusing it. On one of them the description is "white balance > background: blue" and on the other it's "night mode". > > That makes me wonder in what kind of circumstances this control was originally > introduced. Whatever it was, it seems to have taken place before 16th April in > 2005. :-) > > I think we could change the description to something more suitable or just > remove this one... Why remove it ? It's a useful control. And the abuses at the drivers is different story. -- Regards, Sylwester -- 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
