[libcamera-devel] [PATCH 1/1] libcamera: controls: Controls for driving AF (autofocus) algorithms
David Plowman
david.plowman at raspberrypi.com
Tue Mar 15 17:34:23 CET 2022
Hi Hanlin, Jean-Michel, everyone
On Mon, 14 Mar 2022 at 11:06, Hanlin Chen <hanlinchen at chromium.org> wrote:
>
> 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 ?
The file only seems to contain int32_ts so that's what I copied. Am I
allowed other things?
>>
>> > + 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 ?
Thanks, I'll fix this up and all the ones below...
>>
>> > +
>> > + 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'd certainly like CAF (Continuous AF) to be optional. It's a feature
you could choose not to implement as it's quite a lot of work, and
hard to make work well (especially without PDAF).
Something like the "Macro" range... don't mind. We could make it
optional, or define it to be the same as "Normal". What do people
think?
>>
>>
>> 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 ?
Good question. You could imagine a continuous value here, though that
does start to force the developer to do more work, and testing gets
harder. So I feel slightly inclined to leave this as a binary choice,
but am certainly open to persuasion.
>>
>> > + - 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 ?
Stay at the current position. It's your (or the application's) choice
whether to reset the lens. I'll make that clearer.
>>
>> > +
>> > + - 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?
I imagined that these would be "one-shot" things. So you only need to
send them once and they happen.
I imagine there might also be a slight delay between something being
in focus and that feeding back to the application, so you wouldn't
want the algorithm to think "oh, I'm being told to scan again even
though I've only just finished!"
> For AfPauseImmediate, should it only report the state as failed when it's scanning and reset?
So I think if it was "scanning" and gets "AfPauseImmediate", the state
remains "scanning". If it was "focused" when it gets
"AfPauseImmediate", then it stays "focused", and so on. The idea is
that this means you can be sure what state it was in when you sent
"AfPauseImmediate". If we were to change the state you couldn't be
sure whether it was focused or not. This could give an application the
chance to put up a "picture might be blurry" message, for example.
>
>>
>> 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 :-).
I'll look into doing that. Do we have a preferred package? Do I have
to turn it into Ascii Art? :)
Thanks for all the feedback!
David
>>
>>
>> Great work, thanks for it !
>> JM
>>
>> > +
>> > ...
More information about the libcamera-devel
mailing list