[libcamera-devel] [PATCH v2 15/17] android: capabilities: Cap frame rate to 30 FPS

[Jacopo Mondi]

On Wed, Oct 06, 2021 at 04:53:57AM +0300, Laurent Pinchart wrote:
> Hello,
>
> On Wed, Sep 08, 2021 at 09:36:20AM +0900, paul.elder at ideasonboard.com wrote:
> > On Tue, Sep 07, 2021 at 09:41:05PM +0200, Jacopo Mondi wrote:
> > > Limit the reported minumum frame duration to 30 FPS.
> > >
> > > The reason to do is to bring the libcamra HAL in par with the Intel
> > > HAL implementation on IPU3 platform, where 30FPS is the frame rate used
> > > to perform quality tuning in the closed-source IPA module and has been
> > > validated as the most efficient rate for the power/performace budget.
> > >
> > > This change bring into the HAL a platform specific constraints, which
> > > might be opportune for most platforms but should rather be configurable
> > > by system integrators. Record that with a \todo entry.
> > >
> > > Also record that, even if we report a lower frame rate, we currently
> > > do not limit what the camera actually produce.
> >
> > Hm, now I'm starting to wonder if we should cap the reported min frame
> > duration in the HAL, but allow libcamera to go as fast as any user
> > wants. But then we also need a way to actually set the frame duration in
> > libcamera...
> >
> > If the HAL reports max 30fps, then the HAL will only request up to
> > 30fps, and then we can just set that on libcamera's side... that way we
> > satisfy the HAL requirements while keeping the flexibility on
> > libcamera's side.
> >

The problem here is that we have currently no way to 'limit' the frame
rate to 30FPS if not issuing a FrameDuration in each request.

Ideally we should be able to set the desired duration as part of the
StreamConfiguration as we do for the stream size and format.

> > Or would it be better to limit libcamera's IPU3 as well, since 30fps has
> > been confirmed to be the best? "We know what the user wants more than
> > the user knows what they want"
>
> I'd rather go with this patch, I don't think libcamera should limit the
> frame rate artifically on IPU3.

Be aware that wihtout limiting the actual duration to what we report,
we'll have tests failing due to a mismatch in the reported and
calculated durations.

Thanks
  j


>
> > > Signed-off-by: Jacopo Mondi <jacopo at jmondi.org>
> > > ---
> > >  src/android/camera_capabilities.cpp | 23 +++++++++++++++++++++++
> > >  1 file changed, 23 insertions(+)
> > >
> > > diff --git a/src/android/camera_capabilities.cpp b/src/android/camera_capabilities.cpp
> > > index deaec3282fd7..cff1e30a9567 100644
> > > --- a/src/android/camera_capabilities.cpp
> > > +++ b/src/android/camera_capabilities.cpp
> > > @@ -632,6 +632,29 @@ int CameraCapabilities::initializeStreamConfigurations()
> > >
> > >  			int64_t minFrameDuration = frameDurations->second.min().get<int64_t>() * 1000;
> > >  			int64_t maxFrameDuration = frameDurations->second.max().get<int64_t>() * 1000;
> > > +
> > > +			/*
> > > +			 * Cap min frame duration to 30 FPS.
> > > +			 *
> > > +			 * 30 frames per second has been validated as the most
> > > +			 * opportune frame rate for quality tuning, and power
> > > +			 * vs performances budget on Intel IPU3.
>
> I'd say "on Intel IPU3-based Chromebooks", as this budget decision is
> device-specific.
>
> Reviewed-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
>
> > > +			 *
> > > +			 * \todo This is a platform-specific decision that needs
> > > +			 * to be abstracted and delegated to the configuration
> > > +			 * file.
> > > +			 *
> > > +			 * \todo libcamera only allows to control frame duration
> > > +			 * through the per-request controls::FrameDuration
> > > +			 * control. If we cap the durations here, we should be
> > > +			 * capable of configuring the camera to operate at such
> > > +			 * duration without requiring to have the FrameDuration
> > > +			 * control to be specified for each Request. Defer this
> > > +			 * to the in-development configuration API rework.
> > > +			 */
> > > +			if (minFrameDuration < 1e9 / 30.0)
> > > +				minFrameDuration = 1e9 / 30.0;
> > > +
> > >  			streamConfigurations_.push_back({
> > >  				res, androidFormat, minFrameDuration, maxFrameDuration,
> > >  			});
>
> --
> Regards,
>
> Laurent Pinchart