[libcamera-devel] [PATCH v2 1/1] libcamera: controls: Controls for driving AF (autofocus) algorithms
David Plowman
david.plowman at raspberrypi.com
Wed Apr 20 15:02:10 CEST 2022
Hi Jean-Michel
Thanks for raising these points, I think there are some things to
figure out here!
On Fri, 15 Apr 2022 at 09:22, Jean-Michel Hautbois
<jeanmichel.hautbois at ideasonboard.com> wrote:
>
> Hello David,
>
> Now that I'm starting to play a bit with it, I see a few things we might
> want to improve.
>
> On 31/03/2022 17:17, David Plowman wrote:
> > This patch describes a series of controls that allow applications to
> > drive AF algorithms:
> >
> > AfMode - manual, auto or continuous
> > AfLensPosition - set lens position to macro/hyperfocal/infinity
> > AfRange - full, macro or normal
> > AfSpeed - fast or slow
> > AfWindows - AF window locations
> > AfTrigger - start (trigger an AF scan) or cancel
> > AfPause - pause continuous AF
> > LensPosition - position of lens from lens driver
> > AfState - reports the mode, whether scanning/success/failure
> > ---
> > src/libcamera/control_ids.yaml | 373 +++++++++++++++++++++++++++------
> > 1 file changed, 313 insertions(+), 60 deletions(-)
> >
> > diff --git a/src/libcamera/control_ids.yaml b/src/libcamera/control_ids.yaml
> > index 9d4638ae..23607368 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 +630,317 @@ 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
> > + 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.
> > +
> > + An implementation may choose not to implement all the modes.
> > +
> > + 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, but an
> > + application can set controls to move the lens.
> > +
> > + In this mode the AfState will always report AfStateManual.
> > + - 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
> > + AfStateAuto. When a trigger control is sent, AfState will
> > + report AfStateAutoScanning for a period before spontaneously
> > + changing to AfStateAutoFocused or AfStateAutoFailed, 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 AfStateAuto.
> > + - 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 (though it can "pause" them), nor to
> > + move the lens for itself.
> > +
> > + When set to AfModeContinuous, the system will immediately initiate
> > + a scan so AfState will report AfStateContinuousScanning, and will
> > + settle on one of AfStateContinuousFocused or AfStateContinuousFailed,
> > + depending on the scan result.
> > +
> > + - AfLensPosition:
> > + type: int32_t
> > + draft: true
> > + description: |
> > + Control to set the position of the lens to one of the following
> > + predefined locations. This control only has any effect when the AfMode
> > + is set to AfModeManual.
> > +
> > + This control is distinct from the LensPosition control, which sets the
> > + lens position using the lens driver's units.
> > + enum:
> > + - name: AfLensPositionMacro
> > + value: 0
> > + description: The closest focal position of the lens.
> > + - name: AfLensPositionHyperfocal
> > + value: 1
> > + description: Hyperfocal position.
> > + - name: AfLensPositionInfinity
> > + value: 2
> > + description: The furthest focal position (usually infinity).
> > +
> > + - AfRange:
> > + type: int32_t
> > + draft: true
> > + description: |
> > + Control to set the range of focus distances that is scanned. An
> > + implementation may choose not to implement all the options here.
> > + 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.
> > + - 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.
> > +
> > + - AfWindows:
> > + type: Rectangle
> > + draft: true
> > + description: |
> > + Sets the focus windows used by the AF algorithm. The units used express
> > + a proportion of the ScalerCrop control (or if unavailable, of the entire
> > + image), as u0.16 format numbers.
>
> I don't mind using ScalerCrop, but I think it would probably make more
> sense to use the full pixel array ?
The thing that bothers me a bit about the full pixel array is that, if
you use digital zoom, then you will have to update your AfWindows as
they might otherwise lie outside your final image! If it's defined as
being a region of the scaler crop, then it automatically stays the
same (to the application, at least, the pipeline handler probably has
some work to do).
I note that the Android link you give below says "Focus areas are
relative to the current field of view (getZoom())", which I guess is
partly why they use that slightly arbitrary +/-1000 range. Maybe 1000
is easier to work with than the u0.16 format that I specified?
>
> > +
> > + 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.
> > +
> > + size: [platform dependent]
>
> And I would like to point you to this one (you probably already now it):
> https://developer.android.com/reference/android/hardware/Camera.Parameters#getFocusAreas()
>
> I really like the number of areas variable, and even more the weight per
> area. It makes sense, you might want to have more weight in the center,
> but still have a larger region.
>
> I don't get why the corrdinates are between [-1000, 1000] though but...
> not that important.
>
> What do you think ?
Interesting, I'm not quite sure what to make of it. It feels rather
like they don't support traditional multi-spot AF where you focus on
the closest of the regions, not on some average of them. The former
(traditional multi-spot) certainly seems more useful to me. (In fact I
think "averaging" focus regions is a bit misguided, because you have
no a priori information how different the amount of detail might be in
different regions. So a slightly featureless face in the foreground
would get totally overwhelmed by that bush lurking in the background,
pretty much irrespective of the weights you specify.)
In my original proposal there was an AfMethod control. Perhaps we need
to bring it back (with values AfMethodAverage and AfMethodMultiSpot)
to give us both options? In the former case we'd obviously need to add
a per-region weight. Actually, I think we might be able to conjure up
an interesting interpretation for the weights in the multi-spot case,
but perhaps we leave that as "implementation defined" for the moment.
Thoughts? I'm trying to put together the next version of the patch,
but opinions on this in the meantime would be helpful.
Thanks!
David
> JM
>
> > +
> > + - 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 AfModeManual or 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. This does not cause the lens to move
> > + anywhere else. Ignored if no scan is in progress.
> > +
> > + - 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. If the AfState was previously
> > + reporting AfStateContinuousScanning it will now change to
> > + AfStateContinuousScanningPaused, and similarly for
> > + AfStateContinuousFocused and AfStateContinuousFailed.
> > + - name AfPauseDeferred
> > + value: 1
> > + description: |
> > + Pause the continuous autofocus algorithm as soon as it is no longer
> > + scanning. If the AfState is currently reporting
> > + AfStateContinuousFocused is will change to
> > + AfStateContinuousFocusedPaused, and similarly in the case of
> > + AfStateContinuousFailed.
> > +
> > + If AfState reports AfStateContinuousScanning it will change to
> > + AfStateContinuousScanningPausing, and then move to one of
> > + AfStateContinuousFocusedPaused or AfStateContinuousFailedPaused
> > + when the scan completes.
> > + - name: AfPauseResume
> > + value: 2
> > + description: |
> > + Resume continous autofocus operation. The algorithm starts again
> > + from exactly where it left off, and the AfState will drop the
> > + 'Paused' or 'Pausing' part of the 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.
> > +
> > + Note that this control is distinct from AfLensPosition, which allows
> > + the lens to be moved to its macro/hyperfocal/infinity position, rather
> > + than using lens driver units.
> > +
> > + - AfState:
> > + type: int32_t
> > + draft: true
> > + description: |
> > + Reports the current state of the AF algorithm. The possible state changes
> > + are described below, although we add that the following general state
> > + changes are also allowed.
> > +
> > + In any of the AfStateManual or AfStateContinuous states, the AfMode
> > + may be set to AfModeAuto and the algorithm will move to the
> > + AfStateAuto state. If AfTriggerStart is sent at the same time
> > + then the algorithm will move to AfStateAutoScanning state.
> > +
> > + In any of the AfStateAuto or AfStateManual states, the AfMode may
> > + be set to AfModeContinuous and the algorithm will move to
> > + AfStateContinuousScanning.
> > +
> > + In any of the AfStateAuto or AfStateContinuous states, the AfMode may
> > + be set to AfModeManual and the algorithm will move to
> > + AfStateManual. The lens will not be moved and will be left where
> > + it was at that moment.
> > +
> > + enum:
> > + - name: AfStateManual
> > + value: 0
> > + description: |
> > + The AF algorithm is in manual mode (AfModeManual). The LensPosition
> > + and AfLensPosition controls can be used directly to move the lens.
> > + - name: AfStateAuto
> > + value: 1
> > + description: |
> > + The AF algorithm is in auto mode (AfModeAuto), and has either just
> > + been moved into that state, or a scan that was in progress has been
> > + cancelled.
> > + - name: AfStateAutoScanning
> > + value: 2
> > + description: |
> > + The AF algorithm is in auto mode (AfModeAuto), and a scan has been
> > + started using the AfTrigger control. The scan can be cancelled by
> > + sending AfTriggerCancel at which point the algorithm will either
> > + move back to AfStateAuto or, if the scan actually completes
> > + before the cancel request is processed, to one of
> > + AfStateAutoFocused or AfStateAutoFailed.
> > + - name: AfStateAutoFocused
> > + value: 3
> > + description: |
> > + The AF algorithm is in auto mode (AfModeAuto), and a scan has
> > + completed with the result that the algorithm believes the image is
> > + now in focus.
> > + - name: AfStateAutoFailed
> > + value: 4
> > + description: |
> > + The AF algorithm is in auto mode (AfModeAuto), and a scan has
> > + completed with the result that the algorithm did not find a good
> > + focus position.
> > + - name: AfStateContinuousScanning
> > + value: 5
> > + description: |
> > + The AF algorithm is in continuous mode (AfModeContinuous) and
> > + is currently scanning for a good focus position. This occurs when
> > + the mode is first set to AfModeContinuous, or may happen
> > + spontaneously when the algorithm believes a re-scan is needed.
> > + - name: AfStateContinuousScanningPausing
> > + value: 6
> > + description: |
> > + The AF algorithm is in continuous mode (AfModeContinuous) and
> > + was scanning when AfPauseDeferred was sent. The scan will complete
> > + at which point the algorithm moves to the
> > + AfStateContinuousFocusedPaused or AfStateContinuousFailedPaused
> > + state.
> > + - name: AfStateContinuousScanningPaused
> > + value: 7
> > + description: |
> > + The AF algorithm is in continuous mode (AfModeContinuous) and
> > + was scanning when AfPauseImmediate was sent. The scan will not
> > + complete and the algorithm will remain in this state. The scan
> > + may be resumed by sending AfPauseResume.
> > + - name: AfStateContinuousFocused
> > + value: 8
> > + description: |
> > + The AF algorithm is in continuous mode (AfModeContinuous) and
> > + a scan has completed with the algorithm believing it has found a
> > + good focus position.
> > + - name: AfStateContinuousFocusedPaused
> > + value: 9
> > + description: |
> > + The AF algorithm was in the AfStateContinuousFocused state and
> > + has been paused (by either AfPauseImmediate or AfPauseDeferred),
> > + or it was in the AfStateContinuousScanningPausing state and the
> > + scan has completed successfully. The algorithm will now remain
> > + in this state, and may be resumed by sending AfPauseResume.
> > + - name: AfStateContinuousFailed
> > + value: 10
> > + description: |
> > + The AF algorithm is in continuous mode (AfModeContinuous) and
> > + a scan has completed without finding a good focus position.
> > + - name: AfStateContinuousFailedPaused
> > + value: 11
> > + description: |
> > + The AF algorithm was in the AfStateContinuousFailed state and
> > + has been paused (by either AfPauseImmediate or AfPauseDeferred),
> > + or it was in the AfStateContinuousScanningPausing state and the
> > + scan has completed unsuccessfully. The algorithm will now remain
> > + in this state, and may be resumed by sending AfPauseResume.
> > +
> > ...
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