[libcamera-devel] [PATCH 1/3] libcamera: controls: Destage 'SensorTimestamp'

[Jacopo Mondi]

Hi Niklas,

On Fri, Apr 09, 2021 at 11:18:33AM +0200, Niklas Söderlund wrote:
> Hi Jacopo,
>
> Thanks for your work.
>
> On 2021-04-07 18:06:42 +0200, Jacopo Mondi wrote:
> > Destage the 'SensorTimestamp' control, which is used by pipeline
> > handlers to report the time when the first active line of the sensor's
> > pixel array is exposed.
> >
> > Signed-off-by: Jacopo Mondi <jacopo at jmondi.org>
> > ---
> >  src/libcamera/control_ids.yaml | 21 ++++++++++++++-------
> >  1 file changed, 14 insertions(+), 7 deletions(-)
> >
> > diff --git a/src/libcamera/control_ids.yaml b/src/libcamera/control_ids.yaml
> > index b4771f9def89..f025819aedfd 100644
> > --- a/src/libcamera/control_ids.yaml
> > +++ b/src/libcamera/control_ids.yaml
> > @@ -360,6 +360,20 @@ controls:
> >
> >        size: [2]
> >
> > +  - SensorTimestamp:
> > +      type: int64_t
> > +      description: |
> > +        The time when the first row of the image sensor active array is exposed,
> > +        The timestamp represents a monotonically increasing counter since the
> > +        system boot time expressed in nanoseconds.
>
> Is it wise to state that time time counter is increasing since system
> boot?  To me that reads as the counter would start at 0 at system boot
> and that I could calculate uptime from it. Even if this is true on some

If anyone wants to use a frame timestamp to calculate the system
uptime I think he deserves horrible bugs, but I see your point..


> platforms I'm sure there are others where it's not. How about,
>
>     A timestamp when the first row of the image sensor active array is
>     exposed. The timestamp represents a monotonically increasing counter
>     expressed in nanoseconds.
>

I'll drop the "system boot" part

> > +
> > +        Pipeline handlers set this control in a completed Request metadata to
> > +        allow application to compute the sensor's frame period duration by
> > +        comparing consecutive capture results.
> > +
> > +        \todo Define how the sensor timestamp has to be used in the reprocessing
> > +        use case.
> > +
> >    # ----------------------------------------------------------------------------
> >    # Draft controls section
> >
> > @@ -547,13 +561,6 @@ controls:
> >            value: 3
> >            description: The AWB algorithm is locked.
> >
> > -  - SensorTimestamp:
> > -      type: int64_t
> > -      draft: true
> > -      description: |
> > -       Control to report the start of exposure of the first row of the captured
> > -       image. Currently identical to ANDROID_SENSOR_TIMESTAMP.
> > -
> >    - SensorRollingShutterSkew:
> >        type: int64_t
> >        draft: true
> > --
> > 2.31.1
> >
> > _______________________________________________
> > libcamera-devel mailing list
> > libcamera-devel at lists.libcamera.org
> > https://lists.libcamera.org/listinfo/libcamera-devel
>
> --
> Regards,
> Niklas Söderlund