On 06/03/2017 02:57 PM, Sakari Ailus wrote:
On Sat, Jun 03, 2017 at 09:51:39PM +0200, Pavel Machek wrote:
Hi!
+ /* Auto/manual exposure */
+ ctrls->auto_exp = v4l2_ctrl_new_std_menu(hdl, ops,
+ V4L2_CID_EXPOSURE_AUTO,
+ V4L2_EXPOSURE_MANUAL, 0,
+ V4L2_EXPOSURE_AUTO);
+ ctrls->exposure = v4l2_ctrl_new_std(hdl, ops,
+ V4L2_CID_EXPOSURE_ABSOLUTE,
+ 0, 65535, 1, 0);
Is exposure_absolute supposed to be in microseconds...?
Yes.
According to the docs V4L2_CID_EXPOSURE_ABSOLUTE is in 100 usec units.
OTOH V4L2_CID_EXPOSURE has no defined unit, so it's a better fit IMO.
Way more drivers appear to be using EXPOSURE than EXPOSURE_ABSOLUTE, too.
Done, switched to V4L2_CID_EXPOSURE. It's true, this control is not
taking 100 usec units, so unit-less is better.
Thanks. If you know the units, it would be of course better to use
right units...
Steve: what's the unit in this case? Is it lines or something else?
Yes, the register interface for exposure takes lines*16.
Maybe converting from seconds to lines is as simple as
framerate * height * seconds. But I'm not sure about that.
Steve
Pavel: we do need to make sure the user space will be able to know the unit,
too. It's rather a case with a number of controls: the unit is known but
there's no API to convey it to the user.
The exposure is a bit special, too: granularity matters a lot on small
values. On most other controls it does not.
