[libcamera-devel] [PATCH 3/3] src: ipa: raspberrypi: Fix initial AGC oscillation for imx219 sensor

[Naushir Patuck]

Hi Laurent,

On Thu, 26 Nov 2020 at 10:20, Laurent Pinchart <
laurent.pinchart at ideasonboard.com> wrote:

> Hi David,
>
> Thank you for the patch.
>
> On Wed, Nov 25, 2020 at 11:36:40AM +0000, David Plowman wrote:
> > The exposure times in the exposure modes were causing AGC oscillations
> > because the algorithm was demanding long unachievable exposure times
> > but, without working sensor metadata, thought it was getting them when
> > actually it was not. We fix it by making the exposure profile request
> > only achievable exposure times, as we do for the ov5647 tuning.
>
> This looks good to me, and I assume it will still work with sensor
> embedded data, as unachievable exposure times are, well, unachievable
> :-)
>
> Is the process to select shutter values documented in the RPi camera
> documentation, or the tuning tool ? If someone wants to bring up a new
> sensor, how can we ensure a similar bug will not creep in ?
>

My work on FPS control does fix this problem in a generic way for
non-embedded data sensors.  This is done by ensuring we only send exposure
values that will be validated based on vblank limits, thereby ensuring the
return path (without embedded data) will be given the same values used by
the sensor device.   For embedded data sensors,  it all "just works", hence
our preference to use it where available ;-)

Regards,
Naush



>
> > Signed-off-by: David Plowman <david.plowman at raspberrypi.com>
>
> Reviewed-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
>
> > ---
> >  src/ipa/raspberrypi/data/imx219.json | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/src/ipa/raspberrypi/data/imx219.json
> b/src/ipa/raspberrypi/data/imx219.json
> > index b03a7beb..212f8b9a 100644
> > --- a/src/ipa/raspberrypi/data/imx219.json
> > +++ b/src/ipa/raspberrypi/data/imx219.json
> > @@ -133,7 +133,7 @@
> >              {
> >                  "shutter":
> >                  [
> > -                    100, 10000, 30000, 60000, 120000
> > +                    100, 10000, 30000, 30000, 30000
> >                  ],
> >                  "gain":
> >                  [
> > @@ -144,7 +144,7 @@
> >              {
> >                  "shutter":
> >                  [
> > -                    100, 5000, 10000, 20000, 120000
> > +                    100, 5000, 10000, 20000, 30000
> >                  ],
> >                  "gain":
> >                  [
>
> --
> Regards,
>
> Laurent Pinchart
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