Add a jerk tracker to MotionPredictor
This is a no-op
Test: atest libinput_tests
Bug: 266747654
Change-Id: I0f67a1d8ea59a6851afa6f523b6e00b2281745d0
diff --git a/include/input/MotionPredictor.h b/include/input/MotionPredictor.h
index 3b6e401..f715039 100644
--- a/include/input/MotionPredictor.h
+++ b/include/input/MotionPredictor.h
@@ -16,6 +16,7 @@
#pragma once
+#include <array>
#include <cstdint>
#include <memory>
#include <mutex>
@@ -28,6 +29,7 @@
#include <android/sysprop/InputProperties.sysprop.h>
#include <input/Input.h>
#include <input/MotionPredictorMetricsManager.h>
+#include <input/RingBuffer.h>
#include <input/TfLiteMotionPredictor.h>
#include <utils/Timers.h> // for nsecs_t
@@ -37,6 +39,31 @@
return sysprop::InputProperties::enable_motion_prediction().value_or(true);
}
+// Tracker to calculate jerk from motion position samples.
+class JerkTracker {
+public:
+ // Initialize the tracker. If normalizedDt is true, assume that each sample pushed has dt=1.
+ JerkTracker(bool normalizedDt);
+
+ // Add a position to the tracker and update derivative estimates.
+ void pushSample(int64_t timestamp, float xPos, float yPos);
+
+ // Reset JerkTracker for a new motion input.
+ void reset();
+
+ // Return last jerk calculation, if enough samples have been collected.
+ // Jerk is defined as the 3rd derivative of position (change in
+ // acceleration) and has the units of d^3p/dt^3.
+ std::optional<float> jerkMagnitude() const;
+
+private:
+ const bool mNormalizedDt;
+
+ RingBuffer<int64_t> mTimestamps{4};
+ std::array<float, 4> mXDerivatives{}; // [x, x', x'', x''']
+ std::array<float, 4> mYDerivatives{}; // [y, y', y'', y''']
+};
+
/**
* Given a set of MotionEvents for the current gesture, predict the motion. The returned MotionEvent
* contains a set of samples in the future.
@@ -97,6 +124,11 @@
std::unique_ptr<TfLiteMotionPredictorBuffers> mBuffers;
std::optional<MotionEvent> mLastEvent;
+ // mJerkTracker assumes normalized dt = 1 between recorded samples because
+ // the underlying mModel input also assumes fixed-interval samples.
+ // Normalized dt as 1 is also used to correspond with the similar Jank
+ // implementation from the JetPack MotionPredictor implementation.
+ JerkTracker mJerkTracker{true};
std::optional<MotionPredictorMetricsManager> mMetricsManager;