Hi Sylwester,
Sylwester Nawrocki wrote:
Hi Sakari,
On 04/17/2012 06:09 PM, Sakari Ailus wrote:
Hi Sylwester,
On Tue, Apr 17, 2012 at 12:09:51PM +0200, Sylwester Nawrocki wrote:
The V4L2_CID_3A_LOCK bitmask control allows applications to pause
or resume the automatic exposure, focus and wite balance adjustments.
It can be used, for example, to lock the 3A adjustments right before
a still image is captured, for pre-focus, etc.
The applications can control each of the algorithms independently,
through a corresponding control bit, if driver allows that.
How is disabling e.g. focus algorithm different from locking focus?
The difference looks quite obvious to me. When some AUTO control is
switched from auto to manual mode there is no guarantee about the
related parameters the device will end up. E.g. lens may be positioned
into default position, rather than kept at current one, exposure might
be set to manual value from before AE was enabled, etc.
I've seen separate registers at the sensor interfaces for AE, AWB
locking/unlocking and for disabling/enabling those algorithms.
With the proposed control applications can be sure that, for example,
exposure is retained when the V4L2_CID_3A_LOCK is set.
Does it answer your question ?
Yes, it does.
I was thinking how does the situation really differ from disabling the
corresponding automatic algorithm. There may be subtle differences in
practice albeit in principle the two are no different. And if some of the
sensors implement it as lock, then I guess it gives us few options for the
user space interface.
--
Sakari Ailus
sakari.ailus@xxxxxx
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