[libcamera-devel] [PATCH 1/1] libcamera: controls: Add a control for IQ stability

[Kieran Bingham]

Quoting Naushir Patuck via libcamera-devel (2023-09-18 08:53:57)
> Hi David,
> 
> Thank you for this work.
> 
> On Tue, 12 Sept 2023 at 15:23, David Plowman via libcamera-devel
> <libcamera-devel at lists.libcamera.org> wrote:
> >
> > The IqUnstable metadata can be used by IPAs to indicate to an
> > application that they have not settled sufficiently to produce
> > reliable image quality. Applications would be advised to avoid using
> > frames flagged in this way.
> >
> > One example would be when the camera starts, when the AEC/AGC might
> > oscillate for a few frames.
> >
> > Signed-off-by: David Plowman <david.plowman at raspberrypi.com>
> 
> I do like this term better than the more generic startup frames we used before.
> FYI, I have implemented this control in the RPi pipeline handler that
> folks can peek at here:
> https://github.com/naushir/libcamera/tree/iq_stability
> 
> Reviewed-by: Naushir Patuck <naush at raspberrypi.com>
> 
> > ---
> >  src/libcamera/control_ids.yaml | 20 ++++++++++++++++++++
> >  1 file changed, 20 insertions(+)
> >
> > diff --git a/src/libcamera/control_ids.yaml b/src/libcamera/control_ids.yaml
> > index f2e542f4..b96e1272 100644
> > --- a/src/libcamera/control_ids.yaml
> > +++ b/src/libcamera/control_ids.yaml
> > @@ -774,6 +774,26 @@ controls:
> >              Continuous AF is paused. No further state changes or lens movements
> >              will occur until the AfPauseResume control is sent.
> >
> > +  - IqUnstable:
> > +      type: bool
> > +      description: |
> > +        The value true indicates that the camera algorithms have not settled
> > +        sufficiently to generate images of reliable quality. The application
> > +        receiving this frame is advised to drop it and wait for a frame where
> > +        this metadata reports false (or is absent).
> > +
> > +        One example of this would be when the camera system starts. It may be
> > +        trying to adapt very quickly to the ambient conditions, resulting in a
> > +        few frames where the image brightness may be subject to unusually
> > +        extreme oscillations.
> > +
> > +        The control may report true at other times, for example when an HDR mode
> > +        is enabled. Here too there may be a few frames of unpredictable exposure
> > +        until the algorithms have settled.
> > +
> > +        The value false (or absence of the control) indicates that this is a
> > +        normal frame.
> > +

It sounds like this is a flag that tells the application to look at
other aspects too. (Or just ignore or drop the frame).

I.e. the setting of this IqUnstable flag might be because any of the
AWB/AEGC/AF/HDR state machines are not reporting a converged state.

Do the controls for those algorithms already have a way to report their
state? 

I do think a global 'this flag means you need to check things' could
make sense in this instance, but I'm keen to clarify the relationship of
what an application should do here.

It also feels like this could be set 'automatically' by a common layer
that processes metadata before it gets back to the application and would
set it for all pipeline handlers if one of AWB/AEGC/AF/HDR reports an
incorrect state?



> >    # ----------------------------------------------------------------------------
> >    # Draft controls section
> >
> > --
> > 2.30.2
> >