[libcamera-devel] [PATCH 1/1] libcamera: controls: Controls for driving AF (autofocus) algorithms
Jean-Michel Hautbois
jeanmichel.hautbois at ideasonboard.com
Thu Mar 10 15:53:48 CET 2022
Hi David,
Thanks for the patch !
On 10/03/2022 13:05, David Plowman via libcamera-devel wrote:
> This patch describes a series of controls that allow applications to
> drive AF algorithms:
>
> AfMode - manual, auto or continuous
> AfRange - full, macro or normal
> AfSpeed - fast or slow
> AfWindow - AF window locations
> AfTrigger - start (trigger an AF scan) or cancel
> AfPause - pause continuous AF
> LensPosition - position of lens from lens driver
> AfState - reset, scanning, focused or failed
> ---
> src/libcamera/control_ids.yaml | 271 +++++++++++++++++++++++++--------
> 1 file changed, 211 insertions(+), 60 deletions(-)
>
> diff --git a/src/libcamera/control_ids.yaml b/src/libcamera/control_ids.yaml
> index 9d4638ae..89636d82 100644
> --- a/src/libcamera/control_ids.yaml
> +++ b/src/libcamera/control_ids.yaml
> @@ -406,27 +406,6 @@ controls:
> The camera will cancel any active or completed metering sequence.
> The AE algorithm is reset to its initial state.
>
> - - AfTrigger:
> - type: int32_t
> - draft: true
> - description: |
> - Control for AF trigger. Currently identical to
> - ANDROID_CONTROL_AF_TRIGGER.
> -
> - Whether the camera device will trigger autofocus for this request.
> - enum:
> - - name: AfTriggerIdle
> - value: 0
> - description: The trigger is idle.
> - - name: AfTriggerStart
> - value: 1
> - description: The AF routine is started by the camera.
> - - name: AfTriggerCancel
> - value: 2
> - description: |
> - The camera will cancel any active trigger and the AF routine is
> - reset to its initial state.
> -
> - NoiseReductionMode:
> type: int32_t
> draft: true
> @@ -507,45 +486,6 @@ controls:
> The AE algorithm has started a pre-capture metering session.
> \sa AePrecaptureTrigger
>
> - - AfState:
> - type: int32_t
> - draft: true
> - description: |
> - Control to report the current AF algorithm state. Currently identical to
> - ANDROID_CONTROL_AF_STATE.
> -
> - Current state of the AF algorithm.
> - enum:
> - - name: AfStateInactive
> - value: 0
> - description: The AF algorithm is inactive.
> - - name: AfStatePassiveScan
> - value: 1
> - description: |
> - AF is performing a passive scan of the scene in continuous
> - auto-focus mode.
> - - name: AfStatePassiveFocused
> - value: 2
> - description: |
> - AF believes the scene is in focus, but might restart scanning.
> - - name: AfStateActiveScan
> - value: 3
> - description: |
> - AF is performing a scan triggered by an AF trigger request.
> - \sa AfTrigger
> - - name: AfStateFocusedLock
> - value: 4
> - description: |
> - AF believes has focused correctly and has locked focus.
> - - name: AfStateNotFocusedLock
> - value: 5
> - description: |
> - AF has not been able to focus and has locked.
> - - name: AfStatePassiveUnfocused
> - value: 6
> - description: |
> - AF has completed a passive scan without finding focus.
> -
> - AwbState:
> type: int32_t
> draft: true
> @@ -690,4 +630,215 @@ controls:
> value. All of the custom test patterns will be static (that is the
> raw image must not vary from frame to frame).
>
> + - AfMode:
> + type: int32_t
Same open question for almost all: why int32_t and not uint8_t ?
We won't have negative values ? Maybe is it yaml ?
> + draft: true
> + description: |
> + Control to set the mode of the AF (autofocus) algorithm. Applications
> + are allowed to set a new mode, and to send additional controls for
> + that new mode, in the same request.
> + enum:
> + - name: AfModeManual
> + value: 0
> + description: |
> + The AF algorithm is in manual mode. In this mode it will never
> + perform any action nor move the lens of its own accord. The only
> + autofocus controls that have an immediate effect are AfMode (to
> + switch out of manual mode) and LensPosition (so that the lens can
> + be moved "manually").
Alignment changed in the paragraph. I wonder if the part "The only
autofocus [...] "manually")." should be moved in the top description ?
> +
> + In this mode the AfState will always report AfStateReset.
> + - name: AfModeAuto
> + value: 1
> + description: |
> + The AF algorithm is in auto mode. This means that the algorithm
> + will never move the lens or change state unless the AfTrigger
> + control is used. The AfTrigger control can be used to initiate a
> + focus scan, the results of which will also be reported by AfState.
> +
> + If the autofocus algorithm is moved from AfModeAuto to another
> + mode while a scan is in progress, the scan is cancelled
> + immediately, without waiting for the scan to finish.
> +
> + When first entering this mode the AfState will report
Alignment broken ?
> + AfStateReset. When a trigger control is sent, AfState will
> + report AfStateScanning for a period before spontaneously
> + changing to AfStateFocused or AfStateFailed, depending on the
> + outcome of the scan. It will remain in this state until another
> + scan is initiated by the AfTrigger control. If a scan is
> + cancelled (without changing to another mode), AfState will return
> + to AfStateReset.
> + - name: AfModeContinuous
> + value: 2
> + description: |
> + The AF algorithm is in continuous mode. This means that the lens
> + can re-start a scan spontaneously at any moment, without any user
> + intervention. The AfState still reports whether the algorithm is
> + currently scanning or not, though the application has no ability
> + to initiate or cancel scans, nor move the lens for itself.
> +
Alignement broken ?
> + When set to AfModeContinuous, the system will immediately initiate
> + a scan so AfState will report AfStateScanning, and will settle on
> + one of AfStateFocused or AfStateFailed, depending on the scan
> + result.
> +
> + The continuous autofocus behaviour can be paused with the
> + AfPause control. Pausing the algorithm does not change the value
> + reported by AfState, so that applications can determine the
> + state of the algorithm when the pause control took effect. Once
> + un-paused ("resumed"), the algorithm starts again from exactly
> + where it left off when it paused.
I find this difficult to follow without having a state machine in some
drawn way... Is it something we could include in the documentation ?
Seeing which Control changes to which one, which states are then
triggered, etc. ?
> +
> + - AfRange:
> + type: int32_t
> + draft: true
> + description: |
> + Control to set the range of focus distances that is scanned.
> + enum:
> + - name: AfRangeNormal
> + value: 0
> + description: |
> + A wide range of focus distances is scanned, all the way from
> + infinity down to close distances, though depending on the
> + implementation, possibly not including the very closest macro
> + positions.
Alignment broken ?
> + - name: AfRangeMacro
> + value: 1
> + description: Only close distances are scanned.
> + - name: AfRangeFull
> + value: 2
> + description: |
> + The full range of focus distances is scanned just as with
> + AfRangeNormal but this time including the very closest macro
> + positions.
> +
> + - AfSpeed:
> + type: int32_t
> + draft: true
> + description: |
> + Control that determines whether the AF algorithm is to move the lens
> + as quickly as possible or more steadily. For example, during video
> + recording it may be desirable not to move the lens too abruptly, but
> + when in a preview mode (waiting for a still capture) it may be
> + helpful to move the lens as quickly as is reasonably possible.
> + enum:
> + - name: AfSpeedNormal
> + value: 0
> + description: Move the lens at its usual speed.
> + - name: AfSpeedFast
> + value: 1
> + description: Move the lens more quickly.
> +
Can we somehow configure this speed ?
> + - AfWindow:
> + type: Rectangle
> + draft: true
> + description: |
> + Sets the focus windows used by the AF algorithm. The units used express
s/windows/window ?
> + a proportion of the ScalerCrop control (or if unavailable, of the entire
> + image), as u0.16 format numbers.
> +
> + In order to be activated, a rectangle must be programmed with non-zero
> + width and height. If no rectangles are programmed in this way, then the
> + system will choose its own single default window in the centre of the
> + image.
> +
> + The details of how the windows are used are platform dependent. We note
> + that when there is more than one AF window, a typical implementation
> + might find the optimal focus position for each one and finally select
> + the window closest to the camera.
Alignment broken ?
> +
> + size: [platform dependent]
> +
> + - AfTrigger:
> + type: int32_t
> + draft: true
> + description: |
> + This control starts an autofocus scan when AfMode is set to AfModeAuto,
> + and can also be used to terminate a scan early.
> +
> + It is ignored if AfMode is set to AfModeContinuous.
> +
> + enum:
> + - name: AfTriggerStart
> + value: 0
> + description: Start an AF scan. Ignored if a scan is in progress.
> + - name: AfTriggerCancel
> + value: 1
> + description: Cancel an AF scan. Ingored if no scan is in progress.
Does cancelling a scan make the lens stay at its current position ? Or
should it be reset ?
> +
> + - AfPause:
> + type: int32_t
> + draft: true
> + description: |
> + This control has no effect except when in continuous autofocus mode
> + (AfModeContinuous). It can be used to pause any lens movements while
> + (for example) images are captured. The algorithm remains inactive
> + until it is instructed to resume.
> +
> + enum:
> + - name: AfPauseImmediate
> + value: 0
> + description: |
> + Pause the continuous autofocus algorithm immediately, whether or
> + not any kind of scan is underway. The AfState will continue to
> + report whatever value it had when the control was enacted.
> + - name AfPauseDeferred
> + value: 1
> + description: |
> + Pause the continuous autofocus algorithm as soon as it is no longer
> + scanning. The AfState will report AfStateFocused or AfStateFailed,
> + depending on whether the final scan succeeds or not. If no scan is
> + in currently progress, the algorithm will pause immediately.
Alignment broken ?
> + - name: AfPauseResume
> + value: 2
> + description: |
Alignment broken ?
> + Resume continous autofocus operation. The algorithm starts again
> + from exactly where it left off, with AfState unchanged (one of
> + AfStateFocused, AfStateFailed or following AfPauseImmediate it
> + might also have been in the AfStateScanning state).
> +
> + - LensPosition:
> + type: int32_t
> + draft: true
> + description: |
> + Acts as a control to instruct the lens to move to a particular position
> + and also reports back the position of the lens for each frame.
> +
> + The units are determined by the lens driver.
> +
> + The LensPosition control is ignored unless the AfMode is set to
> + AfModeManual.
> +
> + - AfState:
> + type: int32_t
> + draft: true
> + description: |
> + Reports the current state of the AF algorithm.
> + enum:
> + - name: AfStateReset
> + value: 0
> + description: |
> + The AF algorithm reports this state when:
> + * It is in manual mode (AfModeManual).
> + * The system has entered auto mode (AfModeAuto) but no scan
> + has yet been initiated.
> + * The system is in auto mode (AfModeAuto) and a scan has been
> + cancelled.
> + - name: AfStateScanning
> + value: 1
> + description: |
> + AF is performing a scan. This state can be entered spontaneously
> + if AfMode is set to AfModeContinuous, otherwise it requires the
> + application to use the AfTrigger control to start the scan.
> + - name: AfStateFocused
> + value: 2
> + description: |
> + An AF scan has been performed and the algorithm believes the
> + scene is in focus.
> + - name: AfStateFailed
> + value: 3
> + description: |
> + An AF scan has been performed but the algorithm has not been able
> + to find the best focus position.
I confirm my wish of having a graphical state machine :-).
Great work, thanks for it !
JM
> +
> ...
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