[libcamera-devel] [PATCH 1/1] libcamera: controls: Controls for driving AF (autofocus) algorithms
Hanlin Chen
hanlinchen at chromium.org
Mon Mar 14 12:05:50 CET 2022
Hi David, Thanks for the great patch!
On Thu, Mar 10, 2022 at 10:53 PM Jean-Michel Hautbois <
jeanmichel.hautbois at ideasonboard.com> wrote:
> 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.
>
An open question:
Should we make Macro and Continuous mandatory? Or they can be optional
depending on the algorithm implementation?
>
> 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.
>
> Just to confirm. Since we removed the AftriggerIdle, I guess the two
controls AfTriggerStart and AfPauseDeferred should be continuously set
until the state becomes focused or failed? If so, is it better to mention
it in the description?
For AfPauseImmediate, should it only report the state as failed when it's
scanning and reset?
> 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 :-).
>
Vote +1 :-).
>
> Great work, thanks for it !
> JM
>
> > +
> > ...
>
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