[libcamera-devel] [PATCH v5 1/2] libcamera: controls: Add controls for AEC/AGC flicker avoidance

[Umang Jain]

Hi David

On 7/19/23 6:03 PM, Jacopo Mondi via libcamera-devel wrote:
> Hi David
>
> On Tue, Jul 18, 2023 at 03:43:00PM +0100, David Plowman via libcamera-devel wrote:
>> Flicker is the term used to describe brightness banding or oscillation
>> of images caused typically by artificial lighting driven by a 50 or
>> 60Hz mains supply. We add three controls intended to be used by
>> AEC/AGC algorithms:
>>
>> AeFlickerMode to enable flicker avoidance.
>>
>> AeFlickerPeriod to set the flicker period "manually".
>>
>> AeFlickerDetected to report any flicker that is currently detected.
>>
>> Signed-off-by: David Plowman <david.plowman at raspberrypi.com>
>> ---
>>   src/libcamera/control_ids.yaml | 90 +++++++++++++++++++++++++++-------
>>   1 file changed, 73 insertions(+), 17 deletions(-)
>>
>> diff --git a/src/libcamera/control_ids.yaml b/src/libcamera/control_ids.yaml
>> index 056886e6..f2e542f4 100644
>> --- a/src/libcamera/control_ids.yaml
>> +++ b/src/libcamera/control_ids.yaml
>> @@ -156,6 +156,79 @@ controls:
>>           control of which features should be automatically adjusted shouldn't
>>           better be handled through a separate AE mode control.
>>
>> +  - AeFlickerMode:
>> +      type: int32_t
>> +      description: |
>> +        Set the flicker mode, which determines whether, and how, the AGC/AEC
>> +        algorithm attempts to hide flicker effects caused by the duty cycle of
>> +        artificial lighting.
>> +
>> +        Although implementation dependent, many algorithms for "flicker
>> +        avoidance" work by restricting this exposure time to integer multiples
>> +        of the cycle period, wherever possible.
>> +
>> +        Implementations may not support all of the flicker modes listed below.
> I would drop this, PH/IPA are supposed to register only the modes they
> support. This applies generally to all controls

With this addressed,

Reviewed-by: Umang Jain <umang.jain at ideasonboard.com>

>
>> +
>> +        By default the system will start in FlickerAuto mode if this is
>> +        supported, otherwise the flicker mode will be set to FlickerOff.
>> +
>> +      enum:
>> +        - name: FlickerOff
>> +          value: 0
>> +          description: No flicker avoidance is performed.
>> +        - name: FlickerManual
>> +          value: 1
>> +          description: Manual flicker avoidance.
>> +            Suppress flicker effects caused by lighting running with a period
>> +            specified by the AeFlickerPeriod control.
>> +            \sa AeFlickerPeriod
>> +        - name: FlickerAuto
>> +          value: 2
>> +          description: Automatic flicker period detection and avoidance.
>> +            The system will automatically determine the most likely value of
>> +            flicker period, and avoid flicker of this frequency. Once flicker
>> +            is being corrected, it is implementation dependent whether the
>> +            system is still able to detect a change in the flicker period.
>> +            \sa AeFlickerDetected
>> +
>> +  - AeFlickerPeriod:
>> +      type: int32_t
>> +      description: Manual flicker period in microseconds.
>> +        This value sets the current flicker period to avoid. It is used when
>> +        AeFlickerMode is set to FlickerManual.
>> +
>> +        To cancel 50Hz mains flicker, this should be set to 10000 (corresponding
>> +        to 100Hz), or 8333 (120Hz) for 60Hz mains.
>> +
>> +        Setting the mode to FlickerManual when no AeFlickerPeriod has ever been
>> +        set means that no flicker cancellation occurs (until the value of this
>> +        control is updated).
>> +
>> +        Switching to modes other than FlickerManual has no effect on the
>> +        value of the AeFlickerPeriod control.
>> +
>> +        \sa AeFlickerMode
>> +
>> +  - AeFlickerDetected:
>> +      type: int32_t
>> +      description: Flicker period detected in microseconds.
>> +        The value reported here indicates the currently detected flicker
>> +        period, or zero if no flicker at all is detected.
>> +
>> +        When AeFlickerMode is set to FlickerAuto, there may be a period during
>> +        which the value reported here remains zero. Once a non-zero value is
>> +        reported, then this is the flicker period that has been detected and is
>> +        now being cancelled.
>> +
>> +        In the case of 50Hz mains flicker, the value would be 10000
>> +        (corresponding to 100Hz), or 8333 (120Hz) for 60Hz mains flicker.
>> +
>> +        It is implementation dependent whether the system can continue to detect
>> +        flicker of different periods when another frequency is already being
>> +        cancelled.
>> +
>> +        \sa AeFlickerMode
>> +
> Looks good to me
> Reviewed-by: Jacopo Mondi <jacopo.mondi at ideasonboard.com>
>
> Thanks
>    j
>
>>     - Brightness:
>>         type: float
>>         description: |
>> @@ -850,23 +923,6 @@ controls:
>>             value: 1
>>             description: The lens shading map mode is available.
>>
>> -  - SceneFlicker:
>> -      type: int32_t
>> -      draft: true
>> -      description: |
>> -       Control to report the detected scene light frequency. Currently
>> -       identical to ANDROID_STATISTICS_SCENE_FLICKER.
>> -      enum:
>> -        - name: SceneFickerOff
>> -          value: 0
>> -          description: No flickering detected.
>> -        - name: SceneFicker50Hz
>> -          value: 1
>> -          description: 50Hz flickering detected.
>> -        - name: SceneFicker60Hz
>> -          value: 2
>> -          description: 60Hz flickering detected.
>> -
>>     - PipelineDepth:
>>         type: int32_t
>>         draft: true
>> --
>> 2.30.2
>>