[libcamera-devel] [PATCH v3 0/2] Add flicker avoidance controls

[David Plowman]

Hi Laurent

Thanks for the questions!

On Tue, 4 Apr 2023 at 06:46, Laurent Pinchart
<laurent.pinchart at ideasonboard.com> wrote:
>
> Hi David,
>
> On Tue, Mar 28, 2023 at 09:55:19AM +0100, David Plowman via libcamera-devel wrote:
> > Hi everyone
> >
> > Here's an updated version of flicker avoidance controls. It's similar
> > to what I had previously, except that I've split the control which
> > gave an explicit flicker period into two, one for reporting a
> > currently detected value, and another for setting a custom flicker
> > period. So we now have 3 controls in total.
> >
> > In terms of Android, the AeFlickerDetected control corresponds fairly
> > directly to Android's scene_flicker control, which is (from my reading
> > of it) merely reporting any currently detected flicker period.
>
> That's my understanding too.
>
> > AeFlickerDetected, however, allows arbitrary flicker periods
> > to be identified, not just 50 or 60Hz.
>
> Out of curiosity, what are the use cases you envision for other
> frequencies ?

I think the most obvious use cases are when people have LEDs that run
at other frequencies. Probably not such an issue for regular users,
but I could imagine it being useful in lab or technical environments,
and we do have a few of those. But I agree it's not 100% clear, so
alternatives are still definitely worth considering!

Thanks
David

>
> > The other controls (AeFlickerMode and AeFlickerCustom) correspond to
> > Android's anti-banding control. Again, we extend it to allow arbitrary
> > flicker periods.
> >
> > Hope that all makes sense!
> >
> > Thanks
> > David
> >
> > David Plowman (2):
> >   libcamera: controls: Add controls for AEC/AGC flicker avoidance
> >   ipa: raspberrypi: Handle AEC/AGC flicker controls
> >
> >  src/ipa/raspberrypi/raspberrypi.cpp | 80 +++++++++++++++++++++++++++
> >  src/libcamera/control_ids.yaml      | 84 +++++++++++++++++++++++------
> >  2 files changed, 147 insertions(+), 17 deletions(-)
>
> --
> Regards,
>
> Laurent Pinchart