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-rw-r--r--src/ipa/ipu3/algorithms/agc.cpp74
1 files changed, 40 insertions, 34 deletions
diff --git a/src/ipa/ipu3/algorithms/agc.cpp b/src/ipa/ipu3/algorithms/agc.cpp
index 8d6f18f6..a929085c 100644
--- a/src/ipa/ipu3/algorithms/agc.cpp
+++ b/src/ipa/ipu3/algorithms/agc.cpp
@@ -72,7 +72,7 @@ static constexpr double kRelativeLuminanceTarget = 0.16;
Agc::Agc()
: frameCount_(0), lineDuration_(0s), minShutterSpeed_(0s),
- maxShutterSpeed_(0s), filteredExposure_(0s), currentExposure_(0s)
+ maxShutterSpeed_(0s), filteredExposure_(0s)
{
}
@@ -143,33 +143,37 @@ double Agc::measureBrightness(const ipu3_uapi_stats_3a *stats,
/**
* \brief Apply a filter on the exposure value to limit the speed of changes
+ * \param[in] exposureValue The target exposure from the AGC algorithm
+ *
+ * The speed of the filter is adaptive, and will produce the target quicker
+ * during startup, or when the target exposure is within 20% of the most recent
+ * filter output.
+ *
+ * \return The filtered exposure
*/
-void Agc::filterExposure()
+utils::Duration Agc::filterExposure(utils::Duration exposureValue)
{
double speed = 0.2;
- /* Adapt instantly if we are in startup phase */
+ /* Adapt instantly if we are in startup phase. */
if (frameCount_ < kNumStartupFrames)
speed = 1.0;
- if (filteredExposure_ == 0s) {
- /* DG stands for digital gain.*/
- filteredExposure_ = currentExposure_;
- } else {
- /*
- * If we are close to the desired result, go faster to avoid making
- * multiple micro-adjustments.
- * \todo Make this customisable?
- */
- if (filteredExposure_ < 1.2 * currentExposure_ &&
- filteredExposure_ > 0.8 * currentExposure_)
- speed = sqrt(speed);
-
- filteredExposure_ = speed * currentExposure_ +
- filteredExposure_ * (1.0 - speed);
- }
+ /*
+ * If we are close to the desired result, go faster to avoid making
+ * multiple micro-adjustments.
+ * \todo Make this customisable?
+ */
+ if (filteredExposure_ < 1.2 * exposureValue &&
+ filteredExposure_ > 0.8 * exposureValue)
+ speed = sqrt(speed);
+
+ filteredExposure_ = speed * exposureValue +
+ filteredExposure_ * (1.0 - speed);
- LOG(IPU3Agc, Debug) << "After filtering, total_exposure " << filteredExposure_;
+ LOG(IPU3Agc, Debug) << "After filtering, exposure " << filteredExposure_;
+
+ return filteredExposure_;
}
/**
@@ -213,27 +217,29 @@ void Agc::computeExposure(IPAFrameContext &frameContext, double yGain,
* Calculate the current exposure value for the scene as the latest
* exposure value applied multiplied by the new estimated gain.
*/
- currentExposure_ = effectiveExposureValue * evGain;
+ utils::Duration exposureValue = effectiveExposureValue * evGain;
/* Clamp the exposure value to the min and max authorized */
utils::Duration maxTotalExposure = maxShutterSpeed_ * maxAnalogueGain_;
- currentExposure_ = std::min(currentExposure_, maxTotalExposure);
- LOG(IPU3Agc, Debug) << "Target total exposure " << currentExposure_
+ exposureValue = std::min(exposureValue, maxTotalExposure);
+ LOG(IPU3Agc, Debug) << "Target total exposure " << exposureValue
<< ", maximum is " << maxTotalExposure;
- /* \todo: estimate if we need to desaturate */
- filterExposure();
-
- /* Divide the exposure value as new exposure and gain values */
- utils::Duration exposureValue = filteredExposure_;
- utils::Duration shutterTime;
+ /*
+ * Filter the exposure.
+ * \todo: estimate if we need to desaturate
+ */
+ exposureValue = filterExposure(exposureValue);
/*
- * Push the shutter time up to the maximum first, and only then
- * increase the gain.
- */
- shutterTime = std::clamp<utils::Duration>(exposureValue / minAnalogueGain_,
- minShutterSpeed_, maxShutterSpeed_);
+ * Divide the exposure value as new exposure and gain values.
+ *
+ * Push the shutter time up to the maximum first, and only then
+ * increase the gain.
+ */
+ utils::Duration shutterTime =
+ std::clamp<utils::Duration>(exposureValue / minAnalogueGain_,
+ minShutterSpeed_, maxShutterSpeed_);
double stepGain = std::clamp(exposureValue / shutterTime,
minAnalogueGain_, maxAnalogueGain_);
LOG(IPU3Agc, Debug) << "Divided up shutter and gain are "