Re: Gain controls in v4l2-ctrl framework

[Sakari Ailus <sakari.ailus@iki.fi>]

Hi Laurent,

Laurent Pinchart wrote:
> Hi,
>
> On Sunday 23 September 2012 16:20:06 Sakari Ailus wrote:
>> 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
>>> 4: V4L2_CID_GAIN_BLUE
>>> 5: V4L2_CID_GAIN_OFFSET
>>>
>>> I need your opinion's to get moving to add them.
>
> We already have a V4L2_CID_GAIN control and a V4L2_CID_CHROMA_GAIN control in
> the user controls class. I'd like to document how those controls and the new
> proposed gain controls interact. At first glance they don't interact at all,
> devices should not implement both, the user class gain controls are higher-
> level than the controls you proposed - this should still be documented though,
> to make sure driver and application authors will not get confused.
>
> A couple of quick questions about the new controls. Do we also need a common
> gain controls for monochrome sensors ? Is the offset always common for the 4

I think we should have a common gain control for sensors in general, 
whether monochrome or not. Many sensors support global digital gain, 
either only or besides the per-channel gains.

Kind regards,

-- 
Sakari Ailus
sakari.ailus@iki.fi