[libcamera-devel] [PATCH v10 1/3] libcamera: controls: Add frame duration control

[Kieran Bingham]

Hi Naush,

On 18/12/2020 10:06, Naushir Patuck wrote:
> Add an int64_t array control (controls::FrameDurations) to specify the
> minimum and maximum (in that order) frame duration to be used by the
> camera sensor.
> 
> Signed-off-by: Naushir Patuck <naush at raspberrypi.com>
> Reviewed-by: David Plowman <david.plowman at raspberrypi.com>
> Tested-by: David Plowman <david.plowman at raspberrypi.com>
> Reviewed-by: Jacopo Mondi <jacopo at jmondi.org>
> ---
>  src/libcamera/control_ids.yaml | 41 ++++++++++++++++++++++++++++++++++
>  1 file changed, 41 insertions(+)
> 
> diff --git a/src/libcamera/control_ids.yaml b/src/libcamera/control_ids.yaml
> index 6d6f0fee..a58bff18 100644
> --- a/src/libcamera/control_ids.yaml
> +++ b/src/libcamera/control_ids.yaml
> @@ -306,6 +306,47 @@ controls:
>          maximum valid value is given by the properties::ScalerCropMaximum
>          property, and the two can be used to implement digital zoom.
>  
> +  - FrameDurations:
> +      type: int64_t
> +      description: |
> +          The minimum and maximum (in that order) frame duration,
> +          expressed in micro-seconds.
> +
> +          When provided by applications, the control specifies the sensor frame
> +          duration interval the pipeline has to use. This could also limit the
> +          largest exposure time the sensor can use. For example, if a maximum
> +          frame duration of 33ms is requested (corresponding to 30 frames per
> +          second), the sensor will not be able to raise the exposure time above
> +          33ms. A fixed frame duration is achieved by setting the minimum and
> +          maximum values to be the same.
> +
> +          The maximum frame duration provides the absolute limit to the shutter
> +          speed computed by the AE algorithm and it overrides any exposure mode
> +          setting specified with controls::AeExposureMode. Similarly, when a
> +          manual exposure time is set through controls::ExposureTime, it also
> +          gets clipped to the limits set by this control.
> +
> +          \sa AeExposureMode
> +          \sa ExposureTime
> +
> +          \todo Refer to the frame duration limits property to describe how
> +          application-provided values gets clipped and reset.
> +
> +          When reported by pipelines, the control expresses the minimum and
> +          maximum frame durations used after being clipped to what the current
> +          sensor mode supports, and what is achievable based on the exposure
> +          mode setting specified with controls::AeExposureMode or manual
> +          exposure time set through controls::ExposureTime. The sensor frame
> +          duration is one of the parameter that defines the capture frame rate

s/parameter/parameters/ <fixable while applying I expect>

> +          but it does not alone provide enough information to fully calculate it
> +          as it does not account for pipeline processing delays.
> +
> +          \todo Define how to calculate the capture frame rate by
> +          defining controls to report additional delays introduced by
> +          the capture pipeline or post-processing stages (ie JPEG
> +          conversion, frame scaling).

Presumably, the frame rate becomes a function of
  max(FrameDuration, OtherSteps)


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


> +      size: [2]
> +
>    # ----------------------------------------------------------------------------
>    # Draft controls section
>  
> 

-- 
Regards
--
Kieran