[libcamera-devel] [PATCH v2 3/4] ipa: raspberrypi: Pass the maximum allowable shutter speed into the AGC
Naushir Patuck
naush at raspberrypi.com
Wed Jan 27 11:07:58 CET 2021
Hi Laurent,
On Wed, 27 Jan 2021 at 00:17, Laurent Pinchart <
laurent.pinchart at ideasonboard.com> wrote:
> Hi Naush,
>
> Thank you for the patch.
>
> On Sun, Jan 24, 2021 at 02:05:05PM +0000, Naushir Patuck wrote:
> > In order to provide an optimal split between shutter speed and gain, the
> > AGC must know the maximum allowable shutter speed, as limited by the
> > maximum frame duration (either application provided or the default).
> >
> > Add a new API function, SetMaxShutter, to the AgcAlgorihtm class. The
>
> s/AgcAlgorihtm/AgcAlgorithm/
>
> > IPA provides the the maximum shutter speed for AGC calculations.
> > This applies to both the manual and auto AGC modes.
> >
> > Signed-off-by: Naushir Patuck <naush at raspberrypi.com>
> > Reviewed-by: David Plowman <david.plowman at raspberrypi.com>
> > ---
> > .../raspberrypi/controller/agc_algorithm.hpp | 1 +
> > src/ipa/raspberrypi/controller/rpi/agc.cpp | 49 +++++++++++++------
> > src/ipa/raspberrypi/controller/rpi/agc.hpp | 2 +
> > src/ipa/raspberrypi/raspberrypi.cpp | 12 +++++
> > 4 files changed, 49 insertions(+), 15 deletions(-)
> >
> > diff --git a/src/ipa/raspberrypi/controller/agc_algorithm.hpp
> b/src/ipa/raspberrypi/controller/agc_algorithm.hpp
> > index 981f1de2f0e4..f97deb0fca59 100644
> > --- a/src/ipa/raspberrypi/controller/agc_algorithm.hpp
> > +++ b/src/ipa/raspberrypi/controller/agc_algorithm.hpp
> > @@ -19,6 +19,7 @@ public:
> > virtual void SetEv(double ev) = 0;
> > virtual void SetFlickerPeriod(double flicker_period) = 0;
> > virtual void SetFixedShutter(double fixed_shutter) = 0; //
> microseconds
> > + virtual void SetMaxShutter(double max_shutter) = 0; // microseconds
>
> Not something to be addressed now, but would it make sense to express
> durations using std::chrono::duration ? This would avoid the risk of
> passing a value expressed in the wrong unit. Another option would be to
> use double across the code base, using the same unit everywhere (which
> could be seconds, double should give us enough precision).
>
Sorry, forgot to comment about this. I do think it's a great idea to use
std::chrono::duration throughout for time based variables. It reduces so
much of the ambiguity over time bases. When I get a chance, perhaps I'll
have a go within our IPA and controller.
Regards,
Naush
>
> > virtual void SetFixedAnalogueGain(double fixed_analogue_gain) = 0;
> > virtual void SetMeteringMode(std::string const
> &metering_mode_name) = 0;
> > virtual void SetExposureMode(std::string const
> &exposure_mode_name) = 0;
> > diff --git a/src/ipa/raspberrypi/controller/rpi/agc.cpp
> b/src/ipa/raspberrypi/controller/rpi/agc.cpp
> > index eddd1684da12..937bb70ece67 100644
> > --- a/src/ipa/raspberrypi/controller/rpi/agc.cpp
> > +++ b/src/ipa/raspberrypi/controller/rpi/agc.cpp
> > @@ -157,7 +157,7 @@ Agc::Agc(Controller *controller)
> > frame_count_(0), lock_count_(0),
> > last_target_exposure_(0.0),
> > ev_(1.0), flicker_period_(0.0),
> > - fixed_shutter_(0), fixed_analogue_gain_(0.0)
> > + max_shutter_(0), fixed_shutter_(0), fixed_analogue_gain_(0.0)
> > {
> > memset(&awb_, 0, sizeof(awb_));
> > // Setting status_.total_exposure_value_ to zero initially tells us
> > @@ -227,11 +227,23 @@ void Agc::SetFlickerPeriod(double flicker_period)
> > flicker_period_ = flicker_period;
> > }
> >
> > +static double clip_shutter(double shutter, double max_shutter)
> > +{
> > + if (max_shutter)
> > + shutter = std::min(shutter, max_shutter);
> > + return shutter;
> > +}
> > +
> > +void Agc::SetMaxShutter(double max_shutter)
> > +{
> > + max_shutter_ = max_shutter;
> > +}
> > +
> > void Agc::SetFixedShutter(double fixed_shutter)
> > {
> > fixed_shutter_ = fixed_shutter;
> > // Set this in case someone calls Pause() straight after.
> > - status_.shutter_time = fixed_shutter;
> > + status_.shutter_time = clip_shutter(fixed_shutter_, max_shutter_);
>
> Instead of clipping every time the fixed shutter value is accessed,
> wouldn't it be simpler to store the clipped shutter in fixed_shutter_ ?
> This would possibly cause the fixed shutter to be clipped based on the
> current mode and not get increased on mode change, but is that a problem
> ? An application setting the ExposureTime control should expect it to be
> clipped, but should it expect the original value to be remembered ?
>
> An alternative would be to turn clip_shutter() into a GetFixedShutter()
> member function that would use fixed_shutter_ and max_shutter_
> internally and not take any argument. There's one caller that uses the
> function with a different set of arguments, so maybe we would need to
> keep clip_shutter() and add a GetFixedShutter() wrapper.
>
> > }
> >
> > void Agc::SetFixedAnalogueGain(double fixed_analogue_gain)
> > @@ -261,7 +273,8 @@ void Agc::SwitchMode([[maybe_unused]] CameraMode
> const &camera_mode,
> > {
> > housekeepConfig();
> >
> > - if (fixed_shutter_ != 0.0 && fixed_analogue_gain_ != 0.0) {
> > + double fixed_shutter = clip_shutter(fixed_shutter_, max_shutter_);
> > + if (fixed_shutter != 0.0 && fixed_analogue_gain_ != 0.0) {
> > // We're going to reset the algorithm here with these
> fixed values.
> >
> > fetchAwbStatus(metadata);
> > @@ -269,14 +282,14 @@ void Agc::SwitchMode([[maybe_unused]] CameraMode
> const &camera_mode,
> > ASSERT(min_colour_gain != 0.0);
> >
> > // This is the equivalent of computeTargetExposure and
> applyDigitalGain.
> > - target_.total_exposure_no_dg = fixed_shutter_ *
> fixed_analogue_gain_;
> > + target_.total_exposure_no_dg = fixed_shutter *
> fixed_analogue_gain_;
> > target_.total_exposure = target_.total_exposure_no_dg /
> min_colour_gain;
> >
> > // Equivalent of filterExposure. This resets any "history".
> > filtered_ = target_;
> >
> > // Equivalent of divideUpExposure.
> > - filtered_.shutter = fixed_shutter_;
> > + filtered_.shutter = fixed_shutter;
> > filtered_.analogue_gain = fixed_analogue_gain_;
> > } else if (status_.total_exposure_value) {
> > // On a mode switch, it's possible the exposure profile
> could change,
> > @@ -290,7 +303,7 @@ void Agc::SwitchMode([[maybe_unused]] CameraMode
> const &camera_mode,
> > // for any that weren't set.
> >
> > // Equivalent of divideUpExposure.
> > - filtered_.shutter = fixed_shutter_ ? fixed_shutter_ :
> config_.default_exposure_time;
> > + filtered_.shutter = fixed_shutter ? fixed_shutter :
> config_.default_exposure_time;
> > filtered_.analogue_gain = fixed_analogue_gain_ ?
> fixed_analogue_gain_ : config_.default_analogue_gain;
> > }
> >
> > @@ -403,7 +416,8 @@ void Agc::housekeepConfig()
> > {
> > // First fetch all the up-to-date settings, so no one else has to
> do it.
> > status_.ev = ev_;
> > - status_.fixed_shutter = fixed_shutter_;
> > + double fixed_shutter = clip_shutter(fixed_shutter_, max_shutter_);
> > + status_.fixed_shutter = fixed_shutter;
> > status_.fixed_analogue_gain = fixed_analogue_gain_;
> > status_.flicker_period = flicker_period_;
> > LOG(RPiAgc, Debug) << "ev " << status_.ev << " fixed_shutter "
> > @@ -582,13 +596,15 @@ void Agc::computeTargetExposure(double gain)
> > target_.total_exposure = current_.total_exposure_no_dg *
> gain;
> > // The final target exposure is also limited to what the
> exposure
> > // mode allows.
> > + double max_shutter = status_.fixed_shutter != 0.0
> > + ? status_.fixed_shutter
> > + :
> exposure_mode_->shutter.back();
> > + max_shutter = clip_shutter(max_shutter, max_shutter_);
> > double max_total_exposure =
> > - (status_.fixed_shutter != 0.0
> > - ? status_.fixed_shutter
> > - : exposure_mode_->shutter.back()) *
> > + max_shutter *
> > (status_.fixed_analogue_gain != 0.0
> > - ? status_.fixed_analogue_gain
> > - : exposure_mode_->gain.back());
> > + ? status_.fixed_analogue_gain
> > + : exposure_mode_->gain.back());
> > target_.total_exposure = std::min(target_.total_exposure,
> > max_total_exposure);
> > }
> > @@ -671,6 +687,7 @@ void Agc::divideUpExposure()
> > shutter_time = status_.fixed_shutter != 0.0
> > ? status_.fixed_shutter
> > : exposure_mode_->shutter[0];
> > + shutter_time = clip_shutter(shutter_time, max_shutter_);
> > analogue_gain = status_.fixed_analogue_gain != 0.0
> > ? status_.fixed_analogue_gain
> > : exposure_mode_->gain[0];
> > @@ -678,14 +695,16 @@ void Agc::divideUpExposure()
> > for (unsigned int stage = 1;
> > stage < exposure_mode_->gain.size(); stage++) {
> > if (status_.fixed_shutter == 0.0) {
> > - if (exposure_mode_->shutter[stage] *
> > - analogue_gain >=
> > + double stage_shutter =
> > +
> clip_shutter(exposure_mode_->shutter[stage],
> > + max_shutter_);
> > + if (stage_shutter * analogue_gain >=
> > exposure_value) {
> > shutter_time =
> > exposure_value /
> analogue_gain;
> > break;
> > }
> > - shutter_time =
> exposure_mode_->shutter[stage];
> > + shutter_time = stage_shutter;
> > }
> > if (status_.fixed_analogue_gain == 0.0) {
> > if (exposure_mode_->gain[stage] *
> > diff --git a/src/ipa/raspberrypi/controller/rpi/agc.hpp
> b/src/ipa/raspberrypi/controller/rpi/agc.hpp
> > index 05c334e4a1de..2ce3b1a1700a 100644
> > --- a/src/ipa/raspberrypi/controller/rpi/agc.hpp
> > +++ b/src/ipa/raspberrypi/controller/rpi/agc.hpp
> > @@ -78,6 +78,7 @@ public:
> > unsigned int GetConvergenceFrames() const override;
> > void SetEv(double ev) override;
> > void SetFlickerPeriod(double flicker_period) override;
> > + void SetMaxShutter(double max_shutter) override; // microseconds
> > void SetFixedShutter(double fixed_shutter) override; //
> microseconds
> > void SetFixedAnalogueGain(double fixed_analogue_gain) override;
> > void SetMeteringMode(std::string const &metering_mode_name)
> override;
> > @@ -126,6 +127,7 @@ private:
> > std::string constraint_mode_name_;
> > double ev_;
> > double flicker_period_;
> > + double max_shutter_;
> > double fixed_shutter_;
> > double fixed_analogue_gain_;
> > };
> > diff --git a/src/ipa/raspberrypi/raspberrypi.cpp
> b/src/ipa/raspberrypi/raspberrypi.cpp
> > index 30ba9aef9d97..75c9e404dcc1 100644
> > --- a/src/ipa/raspberrypi/raspberrypi.cpp
> > +++ b/src/ipa/raspberrypi/raspberrypi.cpp
> > @@ -1008,6 +1008,18 @@ void IPARPi::applyFrameDurations(double
> minFrameDuration, double maxFrameDuratio
> > libcameraMetadata_.set(controls::FrameDurations,
> > { static_cast<int64_t>(minFrameDuration_),
> > static_cast<int64_t>(maxFrameDuration_)
> });
> > +
> > + /*
> > + * Calculate the maximum exposure time possible for the AGC to use.
> > + * GetVBlanking() will update maxShutter with the largest exposure
> > + * value possible.
> > + */
> > + double maxShutter = std::numeric_limits<double>::max();
> > + helper_->GetVBlanking(maxShutter, minFrameDuration_,
> maxFrameDuration_);
> > +
> > + RPiController::AgcAlgorithm *agc =
> dynamic_cast<RPiController::AgcAlgorithm *>(
> > + controller_.GetAlgorithm("agc"));
> > + agc->SetMaxShutter(maxShutter);
> > }
> >
> > void IPARPi::applyAGC(const struct AgcStatus *agcStatus, ControlList
> &ctrls)
>
> --
> Regards,
>
> Laurent Pinchart
>
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