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libcamera: controls: Controls for driving AF (autofocus) algorithms

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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
AfMetering - how to choose where to measure focus
AfWindows - AF window locations
AfTrigger - start (trigger) an AF scan or cancel
AfPause - pause continuous AF
LensPosition - set or retrieve position of lens
AfState - reports whether scanning/success/failure
AfPauseState - reports whether continuous AF paused or not

Signed-off-by: David Plowman <david.plowman@raspberrypi.com>
Reviewed-by: Jacopo Mondi <jacopo@jmondi.org>
Reviewed-by: Jean-Michel Hautbois <jeanmichel.hautbois@ideasonboard.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
This commit is contained in:
David Plowman 2022-05-16 17:12:24 +01:00 • committed by Laurent Pinchart
parent 153b468930
commit 3e7f54a312
1 changed files with 301 additions and 60 deletions
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361
src/libcamera/control_ids.yaml
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@ -381,6 +381,307 @@ controls:
\todo Define how the sensor timestamp has to be used in the reprocessing
use case.
- AfMode:
type: int32_t
description: |
Control to set the mode of the AF (autofocus) algorithm.
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 specify the desired lens position using the
LensPosition control.
In this mode the AfState will always report AfStateIdle.
- 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 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
AfStateIdle. 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 AfStateIdle.
- 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 to move the lens for itself.
However, applications can pause the AF algorithm from continuously
scanning by using the AfPause control. This allows video or still
images to be captured whilst guaranteeing that the focus is fixed.
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.
- AfRange:
type: int32_t
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
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.
- AfMetering:
type: int32_t
description: |
Instruct the AF algorithm how it should decide which parts of the image
should be used to measure focus.
enum:
- name: AfMeteringAuto
value: 0
description: The AF algorithm should decide for itself where it will
measure focus.
- name: AfMeteringWindows
value: 1
description: The AF algorithm should use the rectangles defined by
the AfWindows control to measure focus. If no windows are specified
the behaviour is platform dependent.
- AfWindows:
type: Rectangle
description: |
Sets the focus windows used by the AF algorithm when AfMetering is set
to AfMeteringWindows. The units used are pixels within the rectangle
returned by the ScalerCropMaximum property.
In order to be activated, a rectangle must be programmed with non-zero
width and height. Internally, these rectangles are intersected with the
ScalerCropMaximum rectangle. If the window becomes empty after this
operation, then the window is ignored. If all the windows end up being
ignored, then the behaviour is platform dependent.
On platforms that support the ScalerCrop control (for implementing
digital zoom, for example), no automatic recalculation or adjustment of
AF windows is performed internally if the ScalerCrop is changed. If any
window lies outside the output image after the scaler crop has been
applied, it is up to the application to recalculate them.
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 where the focal distance for the objects shown in that part
of the image are closest to the camera.
size: [n]
- AfTrigger:
type: int32_t
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
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. AfPauseState will subsequently report
AfPauseStatePaused. AfState may report any of AfStateScanning,
AfStateFocused or AfStateFailed, depending on the algorithm's state
when it received this control.
- name: AfPauseDeferred
value: 1
description: |
This is similar to AfPauseImmediate, and if the AfState is currently
reporting AfStateFocused or AfStateFailed it will remain in that
state and AfPauseState will report AfPauseStatePaused.
However, if the algorithm is scanning (AfStateScanning),
AfPauseState will report AfPauseStatePausing until the scan is
finished, at which point AfState will report one of AfStateFocused
or AfStateFailed, and AfPauseState will change to
AfPauseStatePaused.
- name: AfPauseResume
value: 2
description: |
Resume continuous autofocus operation. The algorithm starts again
from exactly where it left off, and AfPauseState will report
AfPauseStateRunning.
- LensPosition:
type: float
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 LensPosition control is ignored unless the AfMode is set to
AfModeManual, though the value is reported back unconditionally in all
modes.
The units are a reciprocal distance scale like dioptres but normalised
for the hyperfocal distance. That is, for a lens with hyperfocal
distance H, and setting it to a focal distance D, the lens position LP,
which is generally a non-integer, is given by
\f$LP = \frac{H}{D}\f$
For example:
0 moves the lens to infinity.
0.5 moves the lens to twice the hyperfocal distance.
1 moves the lens to the hyperfocal position.
And larger values will focus the lens ever closer.
\todo Define a property to report the Hyperforcal distance of calibrated
lenses.
\todo Define a property to report the maximum and minimum positions of
this lens. The minimum value will often be zero (meaning infinity).
- AfState:
type: int32_t
description: |
Reports the current state of the AF algorithm in conjunction with the
reported AfMode value and (in continuous AF mode) the AfPauseState
value. The possible state changes are described below, though we note
the following state transitions that occur when the AfMode is changed.
If the AfMode is set to AfModeManual, then the AfState will always
report AfStateIdle (even if the lens is subsequently moved). Changing to
the AfModeManual state does not initiate any lens movement.
If the AfMode is set to AfModeAuto then the AfState will report
AfStateIdle. However, if AfModeAuto and AfTriggerStart are sent together
then AfState will omit AfStateIdle and move straight to AfStateScanning
(and start a scan).
If the AfMode is set to AfModeContinuous then the AfState will initially
report AfStateScanning.
enum:
- name: AfStateIdle
value: 0
description: |
The AF algorithm is in manual mode (AfModeManual) or in auto mode
(AfModeAuto) and a scan has not yet been triggered, or an
in-progress scan was cancelled.
- name: AfStateScanning
value: 1
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 AfStateIdle or, if the scan actually completes before
the cancel request is processed, to one of AfStateFocused or
AfStateFailed.
Alternatively the AF algorithm could be in continuous mode
(AfModeContinuous) at which point it may enter this state
spontaneously whenever it determines that a rescan is needed.
- name: AfStateFocused
value: 2
description: |
The AF algorithm is in auto (AfModeAuto) or continuous
(AfModeContinuous) mode and a scan has completed with the result
that the algorithm believes the image is now in focus.
- name: AfStateFailed
value: 3
description: |
The AF algorithm is in auto (AfModeAuto) or continuous
(AfModeContinuous) mode and a scan has completed with the result
that the algorithm did not find a good focus position.
- AfPauseState:
type: int32_t
description: |
Only applicable in continuous (AfModeContinuous) mode, this reports
whether the algorithm is currently running, paused or pausing (that is,
will pause as soon as any in-progress scan completes).
Any change to AfMode will cause AfPauseStateRunning to be reported.
enum:
- name: AfPauseStateRunning
value: 0
description: |
Continuous AF is running and the algorithm may restart a scan
spontaneously.
- name: AfPauseStatePausing
value: 1
description: |
Continuous AF has been sent an AfPauseDeferred control, and will
pause as soon as any in-progress scan completes (and then report
AfPauseStatePaused). No new scans will be start spontaneously until
the AfPauseResume control is sent.
- name: AfPauseStatePaused
value: 2
description: |
Continuous AF is paused. No further state changes or lens movements
will occur until the AfPauseResume control is sent.
# ----------------------------------------------------------------------------
# Draft controls section
@ -406,27 +707,6 @@ 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 +787,6 @@ 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