[libcamera-devel] [PATCH v2 09/11] ipa: af_hill_climb: Skip the first frame after triggering auto focus

[Daniel Semkowicz]

When AFTrigger is received, AF algorithm internal state is reset to
initial values. If reset happens between frames, then first contrast
value that arrives after this, is interpreted as contrast for initial
position. This is wrong, because it was measured for lens position
before the reset. Skip this first frame to allow correct contrast
measure for the initial lens position.

Signed-off-by: Daniel Semkowicz <dse at thaumatec.com>
---
 .../libipa/algorithms/af_hill_climbing.cpp    |  8 +++++++
 src/ipa/libipa/algorithms/af_hill_climbing.h  | 23 ++++++++++++++++++-
 2 files changed, 30 insertions(+), 1 deletion(-)

diff --git a/src/ipa/libipa/algorithms/af_hill_climbing.cpp b/src/ipa/libipa/algorithms/af_hill_climbing.cpp
index f666c6c2..28d09176 100644
--- a/src/ipa/libipa/algorithms/af_hill_climbing.cpp
+++ b/src/ipa/libipa/algorithms/af_hill_climbing.cpp
@@ -84,6 +84,14 @@ namespace ipa::common::algorithms {
  * \return New lens position calculated by AF algorithm
  */
 
+/**
+ * \fn AfHillClimbing::setFramesToSkip()
+ * \brief Request AF to skip n frames
+ * \param[in] n Number of frames to be skipped
+ *
+ * Requested number of frames will not be used for AF calculation.
+ */
+
 } /* namespace ipa::common::algorithms */
 
 } /* namespace libcamera */
diff --git a/src/ipa/libipa/algorithms/af_hill_climbing.h b/src/ipa/libipa/algorithms/af_hill_climbing.h
index db9fc058..e251f3eb 100644
--- a/src/ipa/libipa/algorithms/af_hill_climbing.h
+++ b/src/ipa/libipa/algorithms/af_hill_climbing.h
@@ -29,7 +29,7 @@ public:
 		  lensPosition_(0), bestPosition_(0), currentContrast_(0.0),
 		  previousContrast_(0.0), maxContrast_(0.0), maxStep_(0),
 		  coarseCompleted_(false), fineCompleted_(false),
-		  lowStep_(0), highStep_(kMaxFocusSteps)
+		  lowStep_(0), highStep_(kMaxFocusSteps), framesToSkip_(0)
 	{
 	}
 
@@ -92,6 +92,9 @@ protected:
 	{
 		currentContrast_ = currentContrast;
 
+		if (shouldSkipFrame())
+			return lensPosition_;
+
 		/* If we are in a paused state, we won't process the stats */
 		if (pauseState_ == libcamera::controls::AfPauseStatePaused)
 			return lensPosition_;
@@ -113,6 +116,12 @@ protected:
 		return lensPosition_;
 	}
 
+	void setFramesToSkip(uint32_t n)
+	{
+		if (n > framesToSkip_)
+			framesToSkip_ = n;
+	}
+
 private:
 	void afCoarseScan()
 	{
@@ -191,6 +200,7 @@ private:
 		coarseCompleted_ = false;
 		fineCompleted_ = false;
 		maxContrast_ = 0.0;
+		setFramesToSkip(1);
 	}
 
 	bool afIsOutOfFocus()
@@ -206,6 +216,16 @@ private:
 			return false;
 	}
 
+	bool shouldSkipFrame()
+	{
+		if (framesToSkip_ > 0) {
+			framesToSkip_--;
+			return true;
+		}
+
+		return false;
+	}
+
 	controls::AfModeEnum mode_;
 	controls::AfStateEnum state_;
 	controls::AfPauseStateEnum pauseState_;
@@ -229,6 +249,7 @@ private:
 
 	uint32_t lowStep_;
 	uint32_t highStep_;
+	uint32_t framesToSkip_;
 
 	/*
 	* Maximum focus steps of the VCM control
-- 
2.34.1