commit 5e0e7cf9d7918fac53e21a088e2f7d914cde9b8f
author Derek Wu <derekwu@google.com> Thu Jul 04 11:14:18 2024 +0000
committer Derek Wu <derekwu@google.com> Mon Jul 15 08:10:01 2024 +0000
tree 58476614b8067ea56578eda64f7f8a809858c4e4
parent cda4744d221364232c5860397de3b317cc401687

Add smoothing to jerk calculations and updated jerk thresholds.

Test: atest libinput_tests
Test: atest CtsInputTestCases
Test: atest MotionPredictorBenchmark MotionPredictorTest
Test: Using stylus in a drawing app and seeing the jerk logs.
Bug: 266747654
Bug: 353161308
Flag: com.android.input.flags.enable_prediction_pruning_via_jerk_thresholding
Change-Id: I3d6c47d94d66e5ff2b33474acbca72daca051242

libs/input/MotionPredictor.cpp

diff --git a/libs/input/MotionPredictor.cpp b/libs/input/MotionPredictor.cpp
index 5b61d39..9204b95 100644
--- a/libs/input/MotionPredictor.cpp
+++ b/libs/input/MotionPredictor.cpp
@@ -75,6 +75,9 @@
 JerkTracker::JerkTracker(bool normalizedDt) : mNormalizedDt(normalizedDt) {}
 
 void JerkTracker::pushSample(int64_t timestamp, float xPos, float yPos) {
+    // If we previously had full samples, we have a previous jerk calculation
+    // to do weighted smoothing.
+    const bool applySmoothing = mTimestamps.size() == mTimestamps.capacity();
     mTimestamps.pushBack(timestamp);
     const int numSamples = mTimestamps.size();
 
@@ -115,6 +118,16 @@
         }
     }
 
+    if (numSamples == static_cast<int>(mTimestamps.capacity())) {
+        float newJerkMagnitude = std::hypot(newXDerivatives[3], newYDerivatives[3]);
+        ALOGD_IF(isDebug(), "raw jerk: %f", newJerkMagnitude);
+        if (applySmoothing) {
+            mJerkMagnitude = mJerkMagnitude + (mForgetFactor * (newJerkMagnitude - mJerkMagnitude));
+        } else {
+            mJerkMagnitude = newJerkMagnitude;
+        }
+    }
+
     std::swap(newXDerivatives, mXDerivatives);
     std::swap(newYDerivatives, mYDerivatives);
 }
@@ -125,11 +138,19 @@
 
 std::optional<float> JerkTracker::jerkMagnitude() const {
     if (mTimestamps.size() == mTimestamps.capacity()) {
-        return std::hypot(mXDerivatives[3], mYDerivatives[3]);
+        return mJerkMagnitude;
     }
     return std::nullopt;
 }
 
+void JerkTracker::setForgetFactor(float forgetFactor) {
+    mForgetFactor = forgetFactor;
+}
+
+float JerkTracker::getForgetFactor() const {
+    return mForgetFactor;
+}
+
 // --- MotionPredictor ---
 
 MotionPredictor::MotionPredictor(nsecs_t predictionTimestampOffsetNanos,
@@ -159,6 +180,7 @@
     if (!mModel) {
         mModel = TfLiteMotionPredictorModel::create();
         LOG_ALWAYS_FATAL_IF(!mModel);
+        mJerkTracker.setForgetFactor(mModel->config().jerkForgetFactor);
     }
 
     if (!mBuffers) {
@@ -357,4 +379,12 @@
     return true;
 }
 
+const TfLiteMotionPredictorModel::Config& MotionPredictor::getModelConfig() {
+    if (!mModel) {
+        mModel = TfLiteMotionPredictorModel::create();
+        LOG_ALWAYS_FATAL_IF(!mModel);
+    }
+    return mModel->config();
+}
+
 } // namespace android