Reimplement Chromium's OneEuroFilter to InputConsumer
Reimplemented Chromium's OneEuroFilter usage to InputConsumerNoResampling.
There are a few differences between Chromium's work and this CL. We
reimplemented One Euro filter an adaptive cutoff frequency low pass
made in this implementation as in the Chromium's implementation. The
class FilteredResampler filters the output of LegacyResampler using the
One Euro filter approach.
Here's the link to Chromium's to One Euro filter:
https://source.chromium.org/chromium/chromium/src/+/main:ui/base/prediction/one_euro_filter.h
Bug: 297226446
Flag: EXEMPT bugfix
Test: TEST=libinput_tests; m $TEST && $ANDROID_HOST_OUT/nativetest64/$TEST/$TEST
Change-Id: I0316cb1e81c73b1dc28dc809f55dee3a1cc0ebd2
diff --git a/libs/input/Android.bp b/libs/input/Android.bp
index e4e81ad..a4ae54b 100644
--- a/libs/input/Android.bp
+++ b/libs/input/Android.bp
@@ -217,6 +217,7 @@
],
srcs: [
"AccelerationCurve.cpp",
+ "CoordinateFilter.cpp",
"Input.cpp",
"InputConsumer.cpp",
"InputConsumerNoResampling.cpp",
@@ -230,6 +231,7 @@
"KeyLayoutMap.cpp",
"MotionPredictor.cpp",
"MotionPredictorMetricsManager.cpp",
+ "OneEuroFilter.cpp",
"PrintTools.cpp",
"PropertyMap.cpp",
"Resampler.cpp",
diff --git a/libs/input/CoordinateFilter.cpp b/libs/input/CoordinateFilter.cpp
new file mode 100644
index 0000000..d231474
--- /dev/null
+++ b/libs/input/CoordinateFilter.cpp
@@ -0,0 +1,31 @@
+/**
+ * Copyright 2024 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#define LOG_TAG "CoordinateFilter"
+
+#include <input/CoordinateFilter.h>
+
+namespace android {
+
+CoordinateFilter::CoordinateFilter(float minCutoffFreq, float beta)
+ : mXFilter{minCutoffFreq, beta}, mYFilter{minCutoffFreq, beta} {}
+
+void CoordinateFilter::filter(std::chrono::duration<float> timestamp, PointerCoords& coords) {
+ coords.setAxisValue(AMOTION_EVENT_AXIS_X, mXFilter.filter(timestamp, coords.getX()));
+ coords.setAxisValue(AMOTION_EVENT_AXIS_Y, mYFilter.filter(timestamp, coords.getY()));
+}
+
+} // namespace android
diff --git a/libs/input/OneEuroFilter.cpp b/libs/input/OneEuroFilter.cpp
new file mode 100644
index 0000000..400d7c9
--- /dev/null
+++ b/libs/input/OneEuroFilter.cpp
@@ -0,0 +1,79 @@
+/**
+ * Copyright 2024 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#define LOG_TAG "OneEuroFilter"
+
+#include <chrono>
+#include <cmath>
+
+#include <android-base/logging.h>
+#include <input/CoordinateFilter.h>
+
+namespace android {
+namespace {
+
+inline float cutoffFreq(float minCutoffFreq, float beta, float filteredSpeed) {
+ return minCutoffFreq + beta * std::abs(filteredSpeed);
+}
+
+inline float smoothingFactor(std::chrono::duration<float> samplingPeriod, float cutoffFreq) {
+ return samplingPeriod.count() / (samplingPeriod.count() + (1.0 / (2.0 * M_PI * cutoffFreq)));
+}
+
+inline float lowPassFilter(float rawPosition, float prevFilteredPosition, float smoothingFactor) {
+ return smoothingFactor * rawPosition + (1 - smoothingFactor) * prevFilteredPosition;
+}
+
+} // namespace
+
+OneEuroFilter::OneEuroFilter(float minCutoffFreq, float beta, float speedCutoffFreq)
+ : mMinCutoffFreq{minCutoffFreq}, mBeta{beta}, mSpeedCutoffFreq{speedCutoffFreq} {}
+
+float OneEuroFilter::filter(std::chrono::duration<float> timestamp, float rawPosition) {
+ LOG_IF(FATAL, mPrevFilteredPosition.has_value() && (timestamp <= *mPrevTimestamp))
+ << "Timestamp must be greater than mPrevTimestamp";
+
+ const std::chrono::duration<float> samplingPeriod = (mPrevTimestamp.has_value())
+ ? (timestamp - *mPrevTimestamp)
+ : std::chrono::duration<float>{1.0};
+
+ const float rawVelocity = (mPrevFilteredPosition.has_value())
+ ? ((rawPosition - *mPrevFilteredPosition) / samplingPeriod.count())
+ : 0.0;
+
+ const float speedSmoothingFactor = smoothingFactor(samplingPeriod, mSpeedCutoffFreq);
+
+ const float filteredVelocity = (mPrevFilteredVelocity.has_value())
+ ? lowPassFilter(rawVelocity, *mPrevFilteredVelocity, speedSmoothingFactor)
+ : rawVelocity;
+
+ const float positionCutoffFreq = cutoffFreq(mMinCutoffFreq, mBeta, filteredVelocity);
+
+ const float positionSmoothingFactor = smoothingFactor(samplingPeriod, positionCutoffFreq);
+
+ const float filteredPosition = (mPrevFilteredPosition.has_value())
+ ? lowPassFilter(rawPosition, *mPrevFilteredPosition, positionSmoothingFactor)
+ : rawPosition;
+
+ mPrevTimestamp = timestamp;
+ mPrevRawPosition = rawPosition;
+ mPrevFilteredVelocity = filteredVelocity;
+ mPrevFilteredPosition = filteredPosition;
+
+ return filteredPosition;
+}
+
+} // namespace android
diff --git a/libs/input/Resampler.cpp b/libs/input/Resampler.cpp
index 056db09..3ab132d 100644
--- a/libs/input/Resampler.cpp
+++ b/libs/input/Resampler.cpp
@@ -389,4 +389,34 @@
mLastRealSample = *(mLatestSamples.end() - 1);
}
+// --- FilteredLegacyResampler ---
+
+FilteredLegacyResampler::FilteredLegacyResampler(float minCutoffFreq, float beta)
+ : mResampler{}, mMinCutoffFreq{minCutoffFreq}, mBeta{beta} {}
+
+void FilteredLegacyResampler::resampleMotionEvent(std::chrono::nanoseconds requestedFrameTime,
+ MotionEvent& motionEvent,
+ const InputMessage* futureSample) {
+ mResampler.resampleMotionEvent(requestedFrameTime, motionEvent, futureSample);
+ const size_t numSamples = motionEvent.getHistorySize() + 1;
+ for (size_t sampleIndex = 0; sampleIndex < numSamples; ++sampleIndex) {
+ for (size_t pointerIndex = 0; pointerIndex < motionEvent.getPointerCount();
+ ++pointerIndex) {
+ const int32_t pointerId = motionEvent.getPointerProperties(pointerIndex)->id;
+ const nanoseconds eventTime =
+ nanoseconds{motionEvent.getHistoricalEventTime(sampleIndex)};
+ // Refer to the static function `setMotionEventPointerCoords` for a justification of
+ // casting away const.
+ PointerCoords& pointerCoords = const_cast<PointerCoords&>(
+ *(motionEvent.getHistoricalRawPointerCoords(pointerIndex, sampleIndex)));
+ const auto& [iter, _] = mFilteredPointers.try_emplace(pointerId, mMinCutoffFreq, mBeta);
+ iter->second.filter(eventTime, pointerCoords);
+ }
+ }
+}
+
+std::chrono::nanoseconds FilteredLegacyResampler::getResampleLatency() const {
+ return mResampler.getResampleLatency();
+}
+
} // namespace android
diff --git a/libs/input/tests/Android.bp b/libs/input/tests/Android.bp
index 661c9f7..46e8190 100644
--- a/libs/input/tests/Android.bp
+++ b/libs/input/tests/Android.bp
@@ -25,6 +25,7 @@
"InputVerifier_test.cpp",
"MotionPredictor_test.cpp",
"MotionPredictorMetricsManager_test.cpp",
+ "OneEuroFilter_test.cpp",
"Resampler_test.cpp",
"RingBuffer_test.cpp",
"TestInputChannel.cpp",
diff --git a/libs/input/tests/OneEuroFilter_test.cpp b/libs/input/tests/OneEuroFilter_test.cpp
new file mode 100644
index 0000000..270e789
--- /dev/null
+++ b/libs/input/tests/OneEuroFilter_test.cpp
@@ -0,0 +1,134 @@
+/**
+ * Copyright 2024 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <input/OneEuroFilter.h>
+
+#include <algorithm>
+#include <chrono>
+#include <cmath>
+#include <numeric>
+#include <vector>
+
+#include <gtest/gtest.h>
+
+#include <input/Input.h>
+
+namespace android {
+namespace {
+
+using namespace std::literals::chrono_literals;
+using std::chrono::duration;
+
+struct Sample {
+ duration<double> timestamp{};
+ double value{};
+
+ friend bool operator<(const Sample& lhs, const Sample& rhs) { return lhs.value < rhs.value; }
+};
+
+/**
+ * Generates a sinusoidal signal with the passed frequency and amplitude.
+ */
+std::vector<Sample> generateSinusoidalSignal(duration<double> signalDuration,
+ double samplingFrequency, double signalFrequency,
+ double amplitude) {
+ std::vector<Sample> signal;
+ const duration<double> samplingPeriod{1.0 / samplingFrequency};
+ for (duration<double> timestamp{0.0}; timestamp < signalDuration; timestamp += samplingPeriod) {
+ signal.push_back(
+ Sample{timestamp,
+ amplitude * std::sin(2.0 * M_PI * signalFrequency * timestamp.count())});
+ }
+ return signal;
+}
+
+double meanAbsoluteError(const std::vector<Sample>& filteredSignal,
+ const std::vector<Sample>& signal) {
+ if (filteredSignal.size() != signal.size()) {
+ ADD_FAILURE() << "filteredSignal and signal do not have equal number of samples";
+ return std::numeric_limits<double>::max();
+ }
+ std::vector<double> absoluteError;
+ for (size_t sampleIndex = 0; sampleIndex < signal.size(); ++sampleIndex) {
+ absoluteError.push_back(
+ std::abs(filteredSignal[sampleIndex].value - signal[sampleIndex].value));
+ }
+ if (absoluteError.empty()) {
+ ADD_FAILURE() << "Zero division. absoluteError is empty";
+ return std::numeric_limits<double>::max();
+ }
+ return std::accumulate(absoluteError.begin(), absoluteError.end(), 0.0) / absoluteError.size();
+}
+
+double maxAbsoluteAmplitude(const std::vector<Sample>& signal) {
+ if (signal.empty()) {
+ ADD_FAILURE() << "Max absolute value amplitude does not exist. Signal is empty";
+ return std::numeric_limits<double>::max();
+ }
+ std::vector<Sample> absoluteSignal;
+ for (const Sample& sample : signal) {
+ absoluteSignal.push_back(Sample{sample.timestamp, std::abs(sample.value)});
+ }
+ return std::max_element(absoluteSignal.begin(), absoluteSignal.end())->value;
+}
+
+} // namespace
+
+class OneEuroFilterTest : public ::testing::Test {
+protected:
+ // The constructor's parameters are the ones that Chromium's using. The tuning was based on a 60
+ // Hz sampling frequency. Refer to their one_euro_filter.h header for additional information
+ // about these parameters.
+ OneEuroFilterTest() : mFilter{/*minCutoffFreq=*/4.7, /*beta=*/0.01} {}
+
+ std::vector<Sample> filterSignal(const std::vector<Sample>& signal) {
+ std::vector<Sample> filteredSignal;
+ for (const Sample& sample : signal) {
+ filteredSignal.push_back(
+ Sample{sample.timestamp, mFilter.filter(sample.timestamp, sample.value)});
+ }
+ return filteredSignal;
+ }
+
+ OneEuroFilter mFilter;
+};
+
+TEST_F(OneEuroFilterTest, PassLowFrequencySignal) {
+ const std::vector<Sample> signal =
+ generateSinusoidalSignal(1s, /*samplingFrequency=*/60, /*signalFrequency=*/1,
+ /*amplitude=*/1);
+
+ const std::vector<Sample> filteredSignal = filterSignal(signal);
+
+ // The reason behind using the mean absolute error as a metric is that, ideally, a low frequency
+ // filtered signal is expected to be almost identical to the raw one. Therefore, the error
+ // between them should be minimal. The constant is heuristically chosen.
+ EXPECT_LT(meanAbsoluteError(filteredSignal, signal), 0.25);
+}
+
+TEST_F(OneEuroFilterTest, RejectHighFrequencySignal) {
+ const std::vector<Sample> signal =
+ generateSinusoidalSignal(1s, /*samplingFrequency=*/60, /*signalFrequency=*/22.5,
+ /*amplitude=*/1);
+
+ const std::vector<Sample> filteredSignal = filterSignal(signal);
+
+ // The filtered signal should consist of values that are much closer to zero. The comparison
+ // constant is heuristically chosen.
+ EXPECT_LT(maxAbsoluteAmplitude(filteredSignal), 0.25);
+}
+
+} // namespace android