Hi Chris, On Wednesday 26 September 2012 07:42:41 Chris MacGregor wrote: > On 09/26/2012 12:42 AM, Sakari Ailus wrote: > > On Wed, Sep 26, 2012 at 12:14:36PM +0530, Prabhakar Lad wrote: > >> On Sun, Sep 23, 2012 at 4:56 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 > >>> 4: V4L2_CID_GAIN_BLUE > >>> 5: V4L2_CID_GAIN_OFFSET > >>> > >>> I need your opinion's to get moving to add them. > >> > >> I am listing out the gain controls which is the outcome of above > >> discussion:- > >> > >> 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 > >> 6: V4L2_CID_BLUE_OFFSET > >> 7: V4L2_CID_RED_OFFSET > >> 8: V4L2_CID_GREEN_OFFSET > > > > Hi Prabhakar, > > > > As these are low level controls, I wonder whether it would make sense to > > make a difference between digital and analogue gain. I admit I'm not quite > > as certain whether there's such a large difference as there is for global > > gains for the camera control algorithms. > > Sorry to make this more complicated, but the Aptina MT9P031, for > instance (datasheet at > http://www.aptina.com/assets/downloadDocument.do?id=865 - see page 35), > has Digital Gain, an Analog Multiplier, and Analog Gain (for each of R, > Gr, Gb, and B). For each color channel, there is one register, with the > bits divided up into the three gain types. Furthermore, the different > gain types have different units (increments). > > Currently (at least in the last version I've used), the driver hides all > this and provides a single gain control, and prioritizes which gain > types are adjusted at different user-level gain settings in accordance > with the datasheet recommendations (e.g. keep the analog gain between 1 > and 4 for best noise performance, and use the multiplier for gains > between 4 and 8). This seems very sensible.
I think it should be fine for now. If we later find out that a user space application really needs to control the analog and digital gains individually and precisely we can always split the controls then. For now I think a single gain control (per channel) that groups analog and digital gains should be enough. > If we try to distinguish between analog and digital gains in the control > definitions, what should this driver do? And what about the multiplier? I > suppose it could be "hidden" by the driver as part of the analog gain, as > the driver currently does for the entire gain... -- Regards, Laurent Pinchart -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
