[libcamera-devel] [PATCH v3] android: camera_capabilities: Adjust minimum frame duration to match FPS

[Umang Jain]

Hi

On 4/27/22 20:43, Han-Lin Chen via libcamera-devel wrote:
> CTS calculates FPS with a rounding formula: See
> Camera2SurfaceViewTestCase.java:getSuitableFpsRangeForDuration()
>
> fps = floor(1e9 / minFrameDuration + 0.05f)


It seems(to me at-least) that the placement of the + 0.05f adjustment is 
changed as per this patch.

>
> The android adapter reports it as the AE target FPS. The patch adjusts the
> reported minimum frame duration to match the reported FPS.


Hence we are not introducing any 'new adjustments' rather changing the 
placement of the adjustment.

Given my inference is correct (of course I might be missing the entire 
point here, please do correct me
then), I would re-pharse this commit message  to reflect that this patch 
doesn't introduce any functional
changes.

     android: camera_capabilities: Move minimum frame duration adjustment

     CTS calculates FPS with a rounding formula: See
Camera2SurfaceViewTestCase.java:getSuitableFpsRangeForDuration()

     fps = floor(1e9 / minFrameDuration + 0.05f)

     The android adapter reports it as the AE target FPS. The patch
     moves this adjustment while populating the stream configuration's
     minimum frame duration itself.

What do you think ?

>
> Signed-off-by: Han-Lin Chen <hanlinchen at chromium.org>
> Reviewed-by: Jacopo Mondi <jacopo at jmondi.org>
> ---
>   src/android/camera_capabilities.cpp | 16 +++++++++++-----
>   1 file changed, 11 insertions(+), 5 deletions(-)
>
> diff --git a/src/android/camera_capabilities.cpp b/src/android/camera_capabilities.cpp
> index 55d651f3..ee17cdc7 100644
> --- a/src/android/camera_capabilities.cpp
> +++ b/src/android/camera_capabilities.cpp
> @@ -687,6 +687,14 @@ int CameraCapabilities::initializeStreamConfigurations()
>   					minFrameDuration = minFrameDurationCap;
>   			}
>   
> +			/*
> +			 * Calculate FPS as CTS does and adjust the minimum
> +			 * frame duration accordingly: see
> +			 * Camera2SurfaceViewTestCase.java:getSuitableFpsRangeForDuration()
> +			 */
> +			minFrameDuration =
> +				1e9 / static_cast<unsigned int>(floor(1e9 / minFrameDuration + 0.05f));
> +
>   			streamConfigurations_.push_back({
>   				res, androidFormat, minFrameDuration, maxFrameDuration,
>   			});
> @@ -1287,12 +1295,10 @@ int CameraCapabilities::initializeStaticMetadata()
>   		 * recording profile. Inspecting the Intel IPU3 HAL
>   		 * implementation confirms this but no reference has been found
>   		 * in the metadata documentation.
> -		 *
> -		 * Calculate FPS as CTS does: see
> -		 * Camera2SurfaceViewTestCase.java:getSuitableFpsRangeForDuration()
>   		 */
> -		unsigned int fps = static_cast<unsigned int>
> -				   (floor(1e9 / entry.minFrameDurationNsec + 0.05f));
> +		unsigned int fps =
> +			static_cast<unsigned int>(floor(1e9 / entry.minFrameDurationNsec));
> +
>   		if (entry.androidFormat != HAL_PIXEL_FORMAT_BLOB && fps < 30)
>   			continue;
>