[libcamera-devel] [RFC PATCH v3 05/16] controls: Replace AeLocked with AeState, and add AeLock
Naushir Patuck
naush at raspberrypi.com
Mon Jul 12 16:50:29 CEST 2021
Hi Laurent,
On Sun, 11 Jul 2021 at 23:37, Laurent Pinchart <
laurent.pinchart at ideasonboard.com> wrote:
> Hi Naush,
>
> (now really CC'ing David)
>
> Apologies for the late reply, I should have shared more information on
> this topic earlier.
>
> On Mon, Jul 05, 2021 at 06:34:07PM +0100, Naushir Patuck wrote:
> > On Fri, 2 Jul 2021 at 11:38, Paul Elder wrote:
> > > AeLocked alone isn't sufficient for reporting the AE state, so replace
> > > it with AeState. Add an AeLock control for instructing the camera to
> > > lock the AE values.
> > >
> > > Update the current users of AeLocked accordingly.
> > >
> > > Signed-off-by: Paul Elder <paul.elder at ideasonboard.com>
> > >
> > > ---
> > > No change in v3
> > > ---
> > > src/ipa/raspberrypi/raspberrypi.cpp | 5 +-
> > > src/ipa/rkisp1/rkisp1.cpp | 13 ++--
> > > src/libcamera/control_ids.yaml | 96 ++++++++++++++++++-----------
> > > 3 files changed, 71 insertions(+), 43 deletions(-)
> > >
> > > diff --git a/src/ipa/raspberrypi/raspberrypi.cpp
> b/src/ipa/raspberrypi/raspberrypi.cpp
> > > index 4d09a84f..4981aa29 100644
> > > --- a/src/ipa/raspberrypi/raspberrypi.cpp
> > > +++ b/src/ipa/raspberrypi/raspberrypi.cpp
> > > @@ -469,7 +469,10 @@ void IPARPi::reportMetadata()
> > >
> > > AgcStatus *agcStatus =
> rpiMetadata_.GetLocked<AgcStatus>("agc.status");
> > > if (agcStatus) {
> > > - libcameraMetadata_.set(controls::AeLocked,
> agcStatus->locked);
> > > + libcameraMetadata_.set(controls::AeState,
> > > + agcStatus->locked ?
> > > + controls::AeStateLocked :
> > > + controls::AeStateSearching);
> >
> > Yes, this seems like the correct state mapping.
>
> Is it ? I thought it should be AeStateConverged.
>
> > > libcameraMetadata_.set(controls::DigitalGain,
> agcStatus->digital_gain);
> > > }
> > >
> > > diff --git a/src/ipa/rkisp1/rkisp1.cpp b/src/ipa/rkisp1/rkisp1.cpp
> > > index cdfb4d13..4eca26e2 100644
> > > --- a/src/ipa/rkisp1/rkisp1.cpp
> > > +++ b/src/ipa/rkisp1/rkisp1.cpp
> > > @@ -51,7 +51,7 @@ private:
> > > const rkisp1_stat_buffer *stats);
> > >
> > > void setControls(unsigned int frame);
> > > - void metadataReady(unsigned int frame, unsigned int aeState);
> > > + void metadataReady(unsigned int frame, int aeState);
> > >
> > > std::map<unsigned int, FrameBuffer> buffers_;
> > > std::map<unsigned int, void *> buffersMemory_;
> > > @@ -227,7 +227,7 @@ void IPARkISP1::updateStatistics(unsigned int
> frame,
> > > const rkisp1_stat_buffer *stats)
> > > {
> > > const rkisp1_cif_isp_stat *params = &stats->params;
> > > - unsigned int aeState = 0;
> > > + int aeState = controls::AeStateInactive;
> > >
> > > if (stats->meas_type & RKISP1_CIF_ISP_STAT_AUTOEXP) {
> > > const rkisp1_cif_isp_ae_stat *ae = ¶ms->ae;
> > > @@ -262,7 +262,9 @@ void IPARkISP1::updateStatistics(unsigned int
> frame,
> > > setControls(frame + 1);
> > > }
> > >
> > > - aeState = fabs(factor - 1.0f) < 0.05f ? 2 : 1;
> > > + aeState = fabs(factor - 1.0f) < 0.05f ?
> > > + controls::AeStateConverged :
> > > + controls::AeStateSearching;
> > > }
> > >
> > > metadataReady(frame, aeState);
> > > @@ -281,12 +283,11 @@ void IPARkISP1::setControls(unsigned int frame)
> > > queueFrameAction.emit(frame, op);
> > > }
> > >
> > > -void IPARkISP1::metadataReady(unsigned int frame, unsigned int
> aeState)
> > > +void IPARkISP1::metadataReady(unsigned int frame, int aeState)
> > > {
> > > ControlList ctrls(controls::controls);
> > >
> > > - if (aeState)
> > > - ctrls.set(controls::AeLocked, aeState == 2);
> > > + ctrls.set(controls::AeState, aeState);
> > >
> > > RkISP1Action op;
> > > op.op = ActionMetadata;
> > > diff --git a/src/libcamera/control_ids.yaml
> b/src/libcamera/control_ids.yaml
> > > index 9d4638ae..5717bc1f 100644
> > > --- a/src/libcamera/control_ids.yaml
> > > +++ b/src/libcamera/control_ids.yaml
> > > @@ -14,16 +14,70 @@ controls:
> > >
> > > \sa ExposureTime AnalogueGain
> > >
> > > - - AeLocked:
> > > + - AeLock:
> > > type: bool
> > > description: |
> > > - Report the lock status of a running AE algorithm.
> > > + Control to lock the AE values.
> > > + When set to true, the AE algorithm is locked to its latest
> parameters,
> > > + and will not change exposure settings until set to false.
> > > + \sa AeState
> >
> > I know I am repeating myself here, but I don't see the need to
> differentiate between
> > AeLock and AeEnable == falses.
>
> Please see below.
>
> > > - If the AE algorithm is locked the value shall be set to true,
> if it's
> > > - converging it shall be set to false. If the AE algorithm is
> not
> > > - running the control shall not be present in the metadata
> control list.
> > > + - AeState:
> > > + type: int32_t
> > > + description: |
> > > + Control to report the current AE algorithm state. Enabling or
> disabling
> > > + AE (AeEnable) always resets the AeState to AeStateInactive.
> The camera
> > > + device can do several state transitions between two results,
> if it is
> > > + allowed by the state transition table. For example,
> AeStateInactive may
> > > + never actually be seen in a result.
> > >
> > > - \sa AeEnable
> > > + The state in the result is the state for this image (in sync
> with this
> > > + image). If AE state becomes AeStateConverged, then the image
> data
> > > + associated with the result should be good to use.
> > > +
> > > + The state transitions mentioned below assume that AeEnable is
> on.
> > > +
> > > + \sa AeLock
> > > + enum:
> > > + - name: AeStateInactive
> > > + value: 0
> > > + description: |
> > > + The AE algorithm is inactive.
> > > + If the camera initiates an AE scan, the state shall go to
> Searching.
> > > + If AeLock is on, the state shall go to Locked.
> > >
> >
> > This state is also a bit ambiguous to me. Is this the state that must
> be reported
> > if AeEnable == false? If so, is that not also conveyed by setting the
> latter?
> >
> > If the objective of the change is to wholesale do what Android does,
> then I don't
> > really have any objection to this change as-is, and we can treat the
> above
> > states as best we can in the Raspberry Pi IPA. Otherwise, I do see some
> scope
> > to simplify some of this.
>
> First of all, let me clarify the goal. The libcamera native API needs to
> offer the features required to implement the Android camera HAL API, but
> we don't need to just duplicate it. When there are reasons to depart
> (for instance to fix historical mistakes made in Android, to provide
> additional features, or just to expose an API we consider more
> consistent), we should do so.
>
> Then, a word about the process. Implementing support for an Android
> control requires plumbing it through the camera stack: definition of a
> libcamera control, translation between the Android and libcamera control
> in the Android camera HAL, implementation of the libcamera control in
> the pipeline handlesr, and, when applicable, in the IPAs. Defining
> libcamera controls, as any API design effort, takes time. To allow
> moving forward on all the other parts, we have a fast-track process to
> define draft controls that mimick the Android controls. All the draft
> controls will be redesigned before freezing the libcamera public API.
>
> This means that AeLock and AeState should be marked as draft controls as
> part of this patch.
>
> This being said, we don't need to define controls as draft controls if
> we want to already go through a complete design process. The discussion
> that stemmed from this patch series goes in that direction.
>
> It's useful, in this context, to understand why the Android AE (and AWB)
> controls have been designed this way. Conceptually speaking, the
> algorithms are considered, in Android, to be one level above manual
> controls.
>
> Controls Metadata
> /---------- == OFF ---------\
> | v
> aeMode -/ +------+ |\
> aeLock --> | AE | --> |0\ +--------+
> aeExposureCompensation +------+ | | --> | Sensor | --> exposureTime
> | | +--------+ sensitivity
> exposureTime -----------------------> |1/
> sensitivity |/
>
> (The AE controls are in the adnroid.control class, while the sensor
> manual control are in the android.sensor class.)
>
> The aeMode control selects whether the AE algorithm (when != OFF) or the
> manual controls (when == OFF) drive the sensor. The aeLock control tells
> the AE algorithm to freeze its output (when ON) or operate normally
> (when OFF). The metadata always report the values applied to the sensor,
> regardless of whether they come from the AE algorithm or from manual
> controls.
>
> One important difference, compared to the model we currently implement,
> is that the Android AE algorithm is independent from the manual sensor
> controls. The values of the manual controls aren't affected by the AE
> algorithm, and when AE is disabled, the last set manual control values
> are applied. This thus require an aeLock control to transition
> seamlessly between AE and manual mode, as the application needs to set
> the manual controls to the values applied to the sensor on the last
> frame that AE was on, which couldn't otherwise be done due to the
> internal delays.
>
Thank you for the detailed explanation here. I can now better understand
the Android AE state transitions and why they may be needed.
>
> The existing libcamera AE controls are ill-defined. There's a \todo
> comment to document the interactions between AeEnable and setting a
> fixed value for ExposureTime or AnalogueGain. I'm actually not sure what
> happens if AeEnable is set to false when ExposureTime and/or
> AnalogueGain are 0, or when AeEnable is set to true when ExposureTime
> and/or AnalogueGain are not 0.
>
To provide some brief context on the Raspberry Pi AGC, we never really
go into a "disabled" state at all. This is because the AGC algorithm always
provides the shutter/gain values to pass to the sensor, even in manual mode
(more on this below). We use an internal Paused state to lock the
shutter/gain
values so that they can never change, which essentially mimics a "disabled"
state.
For manual operation, we pass shutter/gain ctrl values (either or both) to
the AGC,
and that is what the AGC requests off the sensor. This happens regardless
of
whether the AGC is in it's internal paused state or not. If the AGC is not
in
paused state, and we only provide one manual control value (e.g. shutter
speed),
then the AGC will vary the gain as it sees fit to converge to the desired
brightness. Setting a manual shutter/gain ctrl value back to 0 hands back
control
of the control to the AGC and it starts adapting it as necessary to
converge to
the desired brightness.
This type of implementation does allow us to essentially do all that
Android would
except of the AGC, but does also allow us the flexibility to do
Aperture/Shutter/Gain
priority modes if needed.
> We need a formal model for how libcamera algorithms interact with manual
> controls. It doesn't have to duplicate the Android model, but it has to
> offer at least the same features. I believe we need to take it one step
> further, as we want to support exposure priority and aperture priority.
> I think we should actually talk about gain/sensitivity priority instead
> of aperture priority for the existing feature, and already prepare for
> devices that have a controllable lens aperture.
>
> Now, the hard question: how should libcamera model this ? :-) Naush,
> David, your feedback from a RPi point of view would be very appreciated.
>
>
It would be easy for me to say do it the Raspberry Pi way :-)
But in reality, I don't think the Android AE model gains us an advantage
over our existing
model. And having to track one less state (locked vs disabled) is always a
good thing.
Explicitly defining AeModes to have (amongst others) ShutterPrioiry,
GainPrioiry,
AperturePriority and Auto modes would be useful though. This avoids the
messiness of
setting 0 to hand back manual control back to the AGC?
I'm sure David will also want to share his opinions on this, but he won't
be able to
respond for a few days.
Regards,
Naush
> Please also let me know if the above explanation is clear or if you need
> more information.
> > + - name: AeStateSearching
> > > + value: 1
> > > + description: |
> > > + The AE algorithm has not converged yet.
> > > + If the camera finishes an AE scan, the state shall go to
> Converged.
> > > + If the camera finishes an AE scan, but flash is required,
> the state
> > > + shall go to FlashRequired.
> > > + If AeLock is on, the state shall go to Locked.
> > > + - name: AeStateConverged
> > > + value: 2
> > > + description: |
> > > + The AE algorithm has converged.
> > > + If the camera initiates an AE scan, the state shall go to
> Searching.
> > > + If AeLock is on, the state shall go to Locked.
> > > + - name: AeStateLocked
> > > + value: 3
> > > + description: |
> > > + The AE algorithm is locked.
> > > + If AeLock is off, the state can go to Searching,
> Converged, or
> > > + FlashRequired.
> > > + - name: AeStateFlashRequired
> > > + value: 4
> > > + description: |
> > > + The AE algorithm would need a flash for good results
> > > + If the camera initiates an AE scan, the state shall go to
> Searching.
> > > + If AeLock is on, the state shall go to Locked.
> > > + - name: AeStatePrecapture
> > > + value: 5
> > > + description: |
> > > + The AE algorithm has started a pre-capture metering
> session.
> > > + After the sequence is finished, the state shall go to
> Converged if
> > > + AeLock is off, and Locked if it is on.
> > > + \sa AePrecaptureTrigger
> > >
> > > # AeMeteringMode needs further attention:
> > > # - Auto-generate max enum value.
> > > @@ -477,36 +531,6 @@ controls:
> > > High quality aberration correction which might reduce the
> frame
> > > rate.
> > >
> > > - - AeState:
> > > - type: int32_t
> > > - draft: true
> > > - description: |
> > > - Control to report the current AE algorithm state. Currently
> identical to
> > > - ANDROID_CONTROL_AE_STATE.
> > > -
> > > - Current state of the AE algorithm.
> > > - enum:
> > > - - name: AeStateInactive
> > > - value: 0
> > > - description: The AE algorithm is inactive.
> > > - - name: AeStateSearching
> > > - value: 1
> > > - description: The AE algorithm has not converged yet.
> > > - - name: AeStateConverged
> > > - value: 2
> > > - description: The AE algorithm has converged.
> > > - - name: AeStateLocked
> > > - value: 3
> > > - description: The AE algorithm is locked.
> > > - - name: AeStateFlashRequired
> > > - value: 4
> > > - description: The AE algorithm would need a flash for good
> results
> > > - - name: AeStatePrecapture
> > > - value: 5
> > > - description: |
> > > - The AE algorithm has started a pre-capture metering
> session.
> > > - \sa AePrecaptureTrigger
> > > -
> > > - AfState:
> > > type: int32_t
> > > draft: true
>
> --
> Regards,
>
> Laurent Pinchart
>
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