On 21/12/16 12:05, Guennadi Liakhovetski wrote:
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:
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.
For compound controls it is currently possible to get the default value
(see the VIDIOC_G_EXT_CTRLS, the documentation for the 'which' field).
This can be extended to MIN/MAX/STEP if needed.
Regards,
Hans
Thanks
Guennadi
--
Regards,
Laurent Pinchart
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