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ipa: rpi: agc: Use channel constraints in the AGC algorithm

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Whenever we run Agc::process(), we store the most recent total
exposure requested for each channel.

With these values we can apply the channel constraints after
time-filtering the requested total exposure, but before working out
how much digital gain is needed.

Signed-off-by: David Plowman <david.plowman@raspberrypi.com>
Reviewed-by: Naushir Patuck <naush@raspberrypi.com>
Reviewed-by: Jacopo Mondi <jacopo.mondi@ideasonboard.com>
Signed-off-by: Jacopo Mondi <jacopo.mondi@ideasonboard.com>
This commit is contained in:
David Plowman 2023-09-15 16:58:44 +01:00 • committed by Jacopo Mondi
parent 7927c44735
commit 7127954aaa
4 changed files with 76 additions and 15 deletions
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60
src/ipa/rpi/controller/rpi/agc_channel.cpp
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@ -493,7 +493,9 @@ void AgcChannel::prepare(Metadata *imageMetadata)
}
}
void AgcChannel::process(StatisticsPtr &stats, DeviceStatus const &deviceStatus, Metadata *imageMetadata)
void AgcChannel::process(StatisticsPtr &stats, DeviceStatus const &deviceStatus,
Metadata *imageMetadata,
const AgcChannelTotalExposures &channelTotalExposures)
{
frameCount_++;
/*
@ -513,11 +515,16 @@ void AgcChannel::process(StatisticsPtr &stats, DeviceStatus const &deviceStatus,
/* 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.
* We may be asked to limit the exposure using other channels. If another channel
* determines our upper bound we may want to know this later.
*/
bool desaturate = applyDigitalGain(gain, targetY);
bool channelBound = applyChannelConstraints(channelTotalExposures);
/*
* Some of the exposure has to be applied as digital gain, so work out
* what that is. It also tells us whether it's trying to desaturate the image
* more quickly, which can only happen when another channel is not limiting us.
*/
bool desaturate = applyDigitalGain(gain, targetY, channelBound);
/*
* The last thing is to divide up the exposure value into a shutter time
* and analogue gain, according to the current exposure mode.
@ -794,7 +801,44 @@ void AgcChannel::computeTargetExposure(double gain)
LOG(RPiAgc, Debug) << "Target totalExposure " << target_.totalExposure;
}
bool AgcChannel::applyDigitalGain(double gain, double targetY)
bool AgcChannel::applyChannelConstraints(const AgcChannelTotalExposures &channelTotalExposures)
{
bool channelBound = false;
LOG(RPiAgc, Debug)
<< "Total exposure before channel constraints " << filtered_.totalExposure;
for (const auto &constraint : config_.channelConstraints) {
LOG(RPiAgc, Debug)
<< "Check constraint: channel " << constraint.channel << " bound "
<< (constraint.bound == AgcChannelConstraint::Bound::UPPER ? "UPPER" : "LOWER")
<< " factor " << constraint.factor;
if (constraint.channel >= channelTotalExposures.size() ||
!channelTotalExposures[constraint.channel]) {
LOG(RPiAgc, Debug) << "no such channel or no exposure available- skipped";
continue;
}
libcamera::utils::Duration limitExposure =
channelTotalExposures[constraint.channel] * constraint.factor;
LOG(RPiAgc, Debug) << "Limit exposure " << limitExposure;
if ((constraint.bound == AgcChannelConstraint::Bound::UPPER &&
filtered_.totalExposure > limitExposure) ||
(constraint.bound == AgcChannelConstraint::Bound::LOWER &&
filtered_.totalExposure < limitExposure)) {
filtered_.totalExposure = limitExposure;
LOG(RPiAgc, Debug) << "Constraint applies";
channelBound = true;
} else
LOG(RPiAgc, Debug) << "Constraint does not apply";
}
LOG(RPiAgc, Debug)
<< "Total exposure after channel constraints " << filtered_.totalExposure;
return channelBound;
}
bool AgcChannel::applyDigitalGain(double gain, double targetY, bool channelBound)
{
double minColourGain = std::min({ awb_.gainR, awb_.gainG, awb_.gainB, 1.0 });
ASSERT(minColourGain != 0.0);
@ -814,8 +858,8 @@ bool AgcChannel::applyDigitalGain(double gain, double targetY)
* quickly (and we then approach the correct value more quickly from
* below).
*/
bool desaturate = targetY > config_.fastReduceThreshold &&
gain < sqrt(targetY);
bool desaturate = !channelBound &&
targetY > config_.fastReduceThreshold && gain < sqrt(targetY);
if (desaturate)
dg /= config_.fastReduceThreshold;
LOG(RPiAgc, Debug) << "Digital gain " << dg << " desaturate? " << desaturate;