[libcamera-devel] [PATCH v2 4/6] fixup! android: camera_device: Compute frame durations

[Laurent Pinchart]

Hi Jacopo,

On Tue, Feb 09, 2021 at 03:50:55AM +0200, Laurent Pinchart wrote:
> On Tue, Jan 26, 2021 at 06:30:06PM +0100, Jacopo Mondi wrote:
> > ---
> >  src/android/camera_device.cpp | 20 ++++++++++++++++++++
> >  1 file changed, 20 insertions(+)
> > 
> > diff --git a/src/android/camera_device.cpp b/src/android/camera_device.cpp
> > index e3d43bea4700..5a8072a8a007 100644
> > --- a/src/android/camera_device.cpp
> > +++ b/src/android/camera_device.cpp
> > @@ -768,6 +768,26 @@ const camera_metadata_t *CameraDevice::getStaticMetadata()
> >  		minFrameDurationUsec = frameDurationsInfo->second.min().get<int64_t>();
> >  		maxFrameDurationUsec = frameDurationsInfo->second.max().get<int64_t>();
> >  
> > +		/*
> > +		 * Adjust the minimum frame duration to comply with Android
> > +		 * requirements. The camera service mandates all preview/record
> > +		 * streams to have a minimum frame duration < 33,366 milliseconds
> > +		 * (see MAX_PREVIEW_RECORD_DURATION_NS in the camera service
> > +		 * implementation).
> > +		 *
> > +		 * If we're close enough (+- 500 useconds) to that value round
> > +		 * the minimum frame duration of the camera to an accepted
> > +		 * value.
> > +		 */
> > +		static constexpr double MIN_PREVIEW_RECORD_FPS = 29.97;
> > +		static constexpr int64_t MAX_PREVIEW_RECORD_DURATION_US = 1e6 / MIN_PREVIEW_RECORD_FPS;
> 
> You could write
> 
> 		static constexpr int64_t MAX_PREVIEW_RECORD_DURATION_US = 1e6 / 29.97;
> 
> as MIN_PREVIEW_RECORD_FPS is only used here.
> 
> > +		if (minFrameDurationUsec > MAX_PREVIEW_RECORD_DURATION_US) {
> > +			double frameDurationDelta = minFrameDurationUsec -
> > +						    MAX_PREVIEW_RECORD_DURATION_US;
> > +			if (frameDurationDelta < 500)
> > +				minFrameDurationUsec = MAX_PREVIEW_RECORD_DURATION_US - 1;
> > +		}
> 
> Is the following more readable ?
> 
> 		if (minFrameDurationUsec > MAX_PREVIEW_RECORD_DURATION_US &&
> 		    minFrameDurationUsec < MAX_PREVIEW_RECORD_DURATION_US + 500) {
> 			minFrameDurationUsec = MAX_PREVIEW_RECORD_DURATION_US - 1;
> 
> This is of course a horrible hack, but if we have no choice...
> 
> Reviewed-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
> 
> What's the maximum FPS we otherwise report ? Is it really that the
> sensor can't reach 30fps, or is there an issue somewhere else ?

Do you have any data regarding this question, why can't we achieve 30fps
without cheating ? I'm also curious, how does the Intel IPU3 HAL handle
this issue ?

> >  		/*
> >  		 * The AE routine frame rate limits are computed using the frame
> >  		 * duration limits, as libcamera clips the AE routine to the

-- 
Regards,

Laurent Pinchart