Implement a second order integrating VT strategy.
Bug: 6413587
Change-Id: I51bc7b8cbff22b10b728fc84ee15370e9984dd55
diff --git a/include/androidfw/VelocityTracker.h b/include/androidfw/VelocityTracker.h
index 262a51b..3e6436a 100644
--- a/include/androidfw/VelocityTracker.h
+++ b/include/androidfw/VelocityTracker.h
@@ -196,7 +196,8 @@
*/
class IntegratingVelocityTrackerStrategy : public VelocityTrackerStrategy {
public:
- IntegratingVelocityTrackerStrategy();
+ // Degree must be 1 or 2.
+ IntegratingVelocityTrackerStrategy(uint32_t degree);
~IntegratingVelocityTrackerStrategy();
virtual void clear();
@@ -209,18 +210,19 @@
// Current state estimate for a particular pointer.
struct State {
nsecs_t updateTime;
- bool first;
+ uint32_t degree;
- float xpos, xvel;
- float ypos, yvel;
+ float xpos, xvel, xaccel;
+ float ypos, yvel, yaccel;
};
+ const uint32_t mDegree;
BitSet32 mPointerIdBits;
State mPointerState[MAX_POINTER_ID + 1];
- static void initState(State& state, nsecs_t eventTime, float xpos, float ypos);
- static void updateState(State& state, nsecs_t eventTime, float xpos, float ypos);
- static void populateEstimator(const State& state, VelocityTracker::Estimator* outEstimator);
+ void initState(State& state, nsecs_t eventTime, float xpos, float ypos) const;
+ void updateState(State& state, nsecs_t eventTime, float xpos, float ypos) const;
+ void populateEstimator(const State& state, VelocityTracker::Estimator* outEstimator) const;
};
} // namespace android
diff --git a/libs/androidfw/VelocityTracker.cpp b/libs/androidfw/VelocityTracker.cpp
index 17cefbe..fc75576 100644
--- a/libs/androidfw/VelocityTracker.cpp
+++ b/libs/androidfw/VelocityTracker.cpp
@@ -182,7 +182,13 @@
// more tolerant of errors. Like 'lsq1', this strategy tends to underestimate
// the velocity of a fling but this strategy tends to respond to changes in
// direction more quickly and accurately.
- return new IntegratingVelocityTrackerStrategy();
+ return new IntegratingVelocityTrackerStrategy(1);
+ }
+ if (!strcmp("int2", strategy)) {
+ // 2nd order integrating filter. Quality: EXPERIMENTAL.
+ // For comparison purposes only. Unlike 'int1' this strategy can compensate
+ // for acceleration but it typically overestimates the effect.
+ return new IntegratingVelocityTrackerStrategy(2);
}
return NULL;
}
@@ -680,7 +686,8 @@
// --- IntegratingVelocityTrackerStrategy ---
-IntegratingVelocityTrackerStrategy::IntegratingVelocityTrackerStrategy() {
+IntegratingVelocityTrackerStrategy::IntegratingVelocityTrackerStrategy(uint32_t degree) :
+ mDegree(degree) {
}
IntegratingVelocityTrackerStrategy::~IntegratingVelocityTrackerStrategy() {
@@ -725,18 +732,20 @@
}
void IntegratingVelocityTrackerStrategy::initState(State& state,
- nsecs_t eventTime, float xpos, float ypos) {
+ nsecs_t eventTime, float xpos, float ypos) const {
state.updateTime = eventTime;
- state.first = true;
+ state.degree = 0;
state.xpos = xpos;
state.xvel = 0;
+ state.xaccel = 0;
state.ypos = ypos;
state.yvel = 0;
+ state.yaccel = 0;
}
void IntegratingVelocityTrackerStrategy::updateState(State& state,
- nsecs_t eventTime, float xpos, float ypos) {
+ nsecs_t eventTime, float xpos, float ypos) const {
const nsecs_t MIN_TIME_DELTA = 2 * NANOS_PER_MS;
const float FILTER_TIME_CONSTANT = 0.010f; // 10 milliseconds
@@ -749,28 +758,45 @@
float xvel = (xpos - state.xpos) / dt;
float yvel = (ypos - state.ypos) / dt;
- if (state.first) {
+ if (state.degree == 0) {
state.xvel = xvel;
state.yvel = yvel;
- state.first = false;
+ state.degree = 1;
} else {
float alpha = dt / (FILTER_TIME_CONSTANT + dt);
- state.xvel += (xvel - state.xvel) * alpha;
- state.yvel += (yvel - state.yvel) * alpha;
+ if (mDegree == 1) {
+ state.xvel += (xvel - state.xvel) * alpha;
+ state.yvel += (yvel - state.yvel) * alpha;
+ } else {
+ float xaccel = (xvel - state.xvel) / dt;
+ float yaccel = (yvel - state.yvel) / dt;
+ if (state.degree == 1) {
+ state.xaccel = xaccel;
+ state.yaccel = yaccel;
+ state.degree = 2;
+ } else {
+ state.xaccel += (xaccel - state.xaccel) * alpha;
+ state.yaccel += (yaccel - state.yaccel) * alpha;
+ }
+ state.xvel += (state.xaccel * dt) * alpha;
+ state.yvel += (state.yaccel * dt) * alpha;
+ }
}
state.xpos = xpos;
state.ypos = ypos;
}
void IntegratingVelocityTrackerStrategy::populateEstimator(const State& state,
- VelocityTracker::Estimator* outEstimator) {
+ VelocityTracker::Estimator* outEstimator) const {
outEstimator->time = state.updateTime;
- outEstimator->degree = 1;
outEstimator->confidence = 1.0f;
+ outEstimator->degree = state.degree;
outEstimator->xCoeff[0] = state.xpos;
outEstimator->xCoeff[1] = state.xvel;
+ outEstimator->xCoeff[2] = state.xaccel / 2;
outEstimator->yCoeff[0] = state.ypos;
outEstimator->yCoeff[1] = state.yvel;
+ outEstimator->yCoeff[2] = state.yaccel / 2;
}
} // namespace android