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ipa: rpi: agc: Filter exposures before dealing with digital gain

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We now time-filter the exposure before sorting out how much digital
gain is required. This is actually a little more natural and
simplifies the code.  It also prepares us for some future work where
this arrangement will be helpful.

Signed-off-by: David Plowman <david.plowman@raspberrypi.com>
Reviewed-by: Naushir Patuck <naush@raspberrpyi.com>
Reviewed-by: Jacopo Mondi <jacopo.mondi@ideasonboard.com>
Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
This commit is contained in:
David Plowman 2023-07-28 14:36:59 +01:00 • committed by Kieran Bingham
parent 2ea57d0b77
commit 84b6327789
2 changed files with 6 additions and 26 deletions
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30
src/ipa/rpi/controller/rpi/agc.cpp
View file

@ -469,14 +469,14 @@ void Agc::process(StatisticsPtr &stats, Metadata *imageMetadata)
computeGain(stats, imageMetadata, gain, targetY);
/* Now compute the target (final) exposure which we think we want. */
computeTargetExposure(gain);
/* The results have to be filtered so as not to change too rapidly. */
filterExposure();
/*
* Some of the exposure has to be applied as digital gain, so work out
* what that is. This function also tells us whether it's decided to
* "desaturate" the image more quickly.
*/
bool desaturate = applyDigitalGain(gain, targetY);
/* The results have to be filtered so as not to change too rapidly. */
filterExposure(desaturate);
/*
* The last thing is to divide up the exposure value into a shutter time
* and analogue gain, according to the current exposure mode.
@ -757,12 +757,12 @@ bool Agc::applyDigitalGain(double gain, double targetY)
if (desaturate)
dg /= config_.fastReduceThreshold;
LOG(RPiAgc, Debug) << "Digital gain " << dg << " desaturate? " << desaturate;
target_.totalExposureNoDG = target_.totalExposure / dg;
LOG(RPiAgc, Debug) << "Target totalExposureNoDG " << target_.totalExposureNoDG;
filtered_.totalExposureNoDG = filtered_.totalExposure / dg;
LOG(RPiAgc, Debug) << "Target totalExposureNoDG " << filtered_.totalExposureNoDG;
return desaturate;
}
void Agc::filterExposure(bool desaturate)
void Agc::filterExposure()
{
double speed = config_.speed;
/*
@ -774,7 +774,6 @@ void Agc::filterExposure(bool desaturate)
speed = 1.0;
if (!filtered_.totalExposure) {
filtered_.totalExposure = target_.totalExposure;
filtered_.totalExposureNoDG = target_.totalExposureNoDG;
} else {
/*
* If close to the result go faster, to save making so many
@ -785,26 +784,7 @@ void Agc::filterExposure(bool desaturate)
speed = sqrt(speed);
filtered_.totalExposure = speed * target_.totalExposure +
filtered_.totalExposure * (1.0 - speed);
/*
* When desaturing, take a big jump down in totalExposureNoDG,
* which we'll hide with digital gain.
*/
if (desaturate)
filtered_.totalExposureNoDG =
target_.totalExposureNoDG;
else
filtered_.totalExposureNoDG =
speed * target_.totalExposureNoDG +
filtered_.totalExposureNoDG * (1.0 - speed);
}
/*
* We can't let the totalExposureNoDG exposure deviate too far below the
* total exposure, as there might not be enough digital gain available
* in the ISP to hide it (which will cause nasty oscillation).
*/
if (filtered_.totalExposureNoDG <
filtered_.totalExposure * config_.fastReduceThreshold)
filtered_.totalExposureNoDG = filtered_.totalExposure * config_.fastReduceThreshold;
LOG(RPiAgc, Debug) << "After filtering, totalExposure " << filtered_.totalExposure
<< " no dg " << filtered_.totalExposureNoDG;
}

2
src/ipa/rpi/controller/rpi/agc.h
View file

@ -93,8 +93,8 @@ private:
void computeGain(StatisticsPtr &statistics, Metadata *imageMetadata,
double &gain, double &targetY);
void computeTargetExposure(double gain);
void filterExposure();
bool applyDigitalGain(double gain, double targetY);
void filterExposure(bool desaturate);
void divideUpExposure();
void writeAndFinish(Metadata *imageMetadata, bool desaturate);
libcamera::utils::Duration limitShutter(libcamera::utils::Duration shutter);