Hi Laurent,

On Tue, 29 Nov 2016, Laurent Pinchart wrote:

Hi Guennadi,

(CC'ing Sakari)

On Monday 28 Nov 2016 15:18:03 Guennadi Liakhovetski wrote:

quoted

Hi,

Has anyone already considered supporting 3A (e.g. auto-exposure) Region of
Interest selection? In UVC this is the "Digital Region of Interest (ROI)
Control." Android defines ANDROID_CONTROL_AE_REGIONS,
ANDROID_CONTROL_AWB_REGIONS, ANDROID_CONTROL_AF_REGIONS. The UVC control
defines just a single rectangle for all (supported) 3A functions. That
could be implemented, defining a new selection target. However, Android
allows arbitrary numbers of ROI rectangles with associated weights. Any
ideas?

Selections could be used, possibly with an update to the API to allow indexing 
selections for a given target. We'd be missing weights though. Another option 
would be to use compound controls.

I talked to Hans online and he is in favour of a compound control for ROI 
as well, which is also fine with me. Working on an implementation I 
realised, that struct v4l2_query_ext_ctrl has min, max, step and default 
values as 64-bit fields, which isn't enough for ROI. Shall they all be 
replaced with unions of original values and pointers? As long as pointers 
don't exceed 64 bits, we'll stay binary compatible. Or do we use those 
fields similar to the STRING type to specify min, max, default number of 
ROIs and a size of one ROI in step? I guess we should go with the latter.

Thanks
Guennadi

-- 
Regards,

Laurent Pinchart