[libcamera-devel] [PATCH v3 16/16] android: capabilities: Cap frame rate to 30 FPS

[Kieran Bingham]

Quoting Jacopo Mondi (2021-10-11 16:11:54)
> 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.
> 
> Signed-off-by: Jacopo Mondi <jacopo at jmondi.org>
> Reviewed-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
> ---
>  src/android/camera_capabilities.cpp | 24 ++++++++++++++++++++++++
>  1 file changed, 24 insertions(+)
> 
> diff --git a/src/android/camera_capabilities.cpp b/src/android/camera_capabilities.cpp
> index fbce816c5f61..0d72a1ff07fa 100644
> --- a/src/android/camera_capabilities.cpp
> +++ b/src/android/camera_capabilities.cpp
> @@ -635,6 +635,30 @@ 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-based
> +                        * Chromebooks.
> +                        *
> +                        * \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;
> +

It would be nice to be using std::chrono::durations or something here to
be able to use 1s/30 or perhaps some other friendly way of describing
frame rates..

But I guess that needs considerably more changes so it doesn't need to
be part of this:


Reviewed-by: Kieran Bingham <kieran.bingham at ideasonboard.com>


>                         streamConfigurations_.push_back({
>                                 res, androidFormat, minFrameDuration, maxFrameDuration,
>                         });
> -- 
> 2.33.0
>