Revision 4aa69d2ae519fd9d074c15b198cb9d12bd4b2ac9 authored by Christian Holler on 22 January 2014, 13:37:53 UTC, committed by Christian Holler on 22 January 2014, 13:37:53 UTC
1 parent 22a18dc
ProcessOrientation.cpp
/*
* Copyright (c) 2013, Linux Foundation. All rights reserved
*
* Copyright (C) 2008 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 "base/basictypes.h"
#include "mozilla/Hal.h"
#include "nsIScreen.h"
#include "nsIScreenManager.h"
#include "OrientationObserver.h"
#include "ProcessOrientation.h"
#include "mozilla/HalSensor.h"
#include "math.h"
#include "limits.h"
#include "android/log.h"
#if 0
#define LOGD(args...) __android_log_print(ANDROID_LOG_DEBUG, "ProcessOrientation" , ## args)
#else
#define LOGD(args...)
#endif
namespace mozilla {
// We work with all angles in degrees in this class.
#define RADIANS_TO_DEGREES (180/M_PI)
// Number of nanoseconds per millisecond.
#define NANOS_PER_MS 1000000
// Indices into SensorEvent.values for the accelerometer sensor.
#define ACCELEROMETER_DATA_X 0
#define ACCELEROMETER_DATA_Y 1
#define ACCELEROMETER_DATA_Z 2
// The minimum amount of time that a predicted rotation must be stable before
// it is accepted as a valid rotation proposal. This value can be quite small
// because the low-pass filter already suppresses most of the noise so we're
// really just looking for quick confirmation that the last few samples are in
// agreement as to the desired orientation.
#define PROPOSAL_SETTLE_TIME_NANOS (40*NANOS_PER_MS)
// The minimum amount of time that must have elapsed since the device last
// exited the flat state (time since it was picked up) before the proposed
// rotation can change.
#define PROPOSAL_MIN_TIME_SINCE_FLAT_ENDED_NANOS (500*NANOS_PER_MS)
// The minimum amount of time that must have elapsed since the device stopped
// swinging (time since device appeared to be in the process of being put down
// or put away into a pocket) before the proposed rotation can change.
#define PROPOSAL_MIN_TIME_SINCE_SWING_ENDED_NANOS (300*NANOS_PER_MS)
// The minimum amount of time that must have elapsed since the device stopped
// undergoing external acceleration before the proposed rotation can change.
#define PROPOSAL_MIN_TIME_SINCE_ACCELERATION_ENDED_NANOS (500*NANOS_PER_MS)
// If the tilt angle remains greater than the specified angle for a minimum of
// the specified time, then the device is deemed to be lying flat
// (just chillin' on a table).
#define FLAT_ANGLE 75
#define FLAT_TIME_NANOS (1000*NANOS_PER_MS)
// If the tilt angle has increased by at least delta degrees within the
// specified amount of time, then the device is deemed to be swinging away
// from the user down towards flat (tilt = 90).
#define SWING_AWAY_ANGLE_DELTA 20
#define SWING_TIME_NANOS (300*NANOS_PER_MS)
// The maximum sample inter-arrival time in milliseconds. If the acceleration
// samples are further apart than this amount in time, we reset the state of
// the low-pass filter and orientation properties. This helps to handle
// boundary conditions when the device is turned on, wakes from suspend or
// there is a significant gap in samples.
#define MAX_FILTER_DELTA_TIME_NANOS (1000*NANOS_PER_MS)
// The acceleration filter time constant.
//
// This time constant is used to tune the acceleration filter such that
// impulses and vibrational noise (think car dock) is suppressed before we try
// to calculate the tilt and orientation angles.
//
// The filter time constant is related to the filter cutoff frequency, which
// is the frequency at which signals are attenuated by 3dB (half the passband
// power). Each successive octave beyond this frequency is attenuated by an
// additional 6dB.
//
// Given a time constant t in seconds, the filter cutoff frequency Fc in Hertz
// is given by Fc = 1 / (2pi * t).
//
// The higher the time constant, the lower the cutoff frequency, so more noise
// will be suppressed.
//
// Filtering adds latency proportional the time constant (inversely
// proportional to the cutoff frequency) so we don't want to make the time
// constant too large or we can lose responsiveness. Likewise we don't want
// to make it too small or we do a poor job suppressing acceleration spikes.
// Empirically, 100ms seems to be too small and 500ms is too large. Android
// default is 200.
#define FILTER_TIME_CONSTANT_MS 200.0f
// State for orientation detection. Thresholds for minimum and maximum
// allowable deviation from gravity.
//
// If the device is undergoing external acceleration (being bumped, in a car
// that is turning around a corner or a plane taking off) then the magnitude
// may be substantially more or less than gravity. This can skew our
// orientation detection by making us think that up is pointed in a different
// direction.
//
// Conversely, if the device is in freefall, then there will be no gravity to
// measure at all. This is problematic because we cannot detect the orientation
// without gravity to tell us which way is up. A magnitude near 0 produces
// singularities in the tilt and orientation calculations.
//
// In both cases, we postpone choosing an orientation.
//
// However, we need to tolerate some acceleration because the angular momentum
// of turning the device can skew the observed acceleration for a short period
// of time.
#define NEAR_ZERO_MAGNITUDE 1 // m/s^2
#define ACCELERATION_TOLERANCE 4 // m/s^2
#define STANDARD_GRAVITY 9.80665f
#define MIN_ACCELERATION_MAGNITUDE (STANDARD_GRAVITY-ACCELERATION_TOLERANCE)
#define MAX_ACCELERATION_MAGNITUDE (STANDARD_GRAVITY+ACCELERATION_TOLERANCE)
// Maximum absolute tilt angle at which to consider orientation data. Beyond
// this (i.e. when screen is facing the sky or ground), we completely ignore
// orientation data.
#define MAX_TILT 75
// The gap angle in degrees between adjacent orientation angles for
// hysteresis.This creates a "dead zone" between the current orientation and a
// proposed adjacent orientation. No orientation proposal is made when the
// orientation angle is within the gap between the current orientation and the
// adjacent orientation.
#define ADJACENT_ORIENTATION_ANGLE_GAP 45
const int
ProcessOrientation::tiltTolerance[][4] = {
{-25, 70}, // ROTATION_0
{-25, 65}, // ROTATION_90
{-25, 60}, // ROTATION_180
{-25, 65} // ROTATION_270
};
int
ProcessOrientation::GetProposedRotation()
{
return mProposedRotation;
}
int
ProcessOrientation::OnSensorChanged(const SensorData& event,
int deviceCurrentRotation)
{
// The vector given in the SensorEvent points straight up (towards the sky)
// under ideal conditions (the phone is not accelerating). I'll call this up
// vector elsewhere.
const InfallibleTArray<float>& values = event.values();
float x = values[ACCELEROMETER_DATA_X];
float y = values[ACCELEROMETER_DATA_Y];
float z = values[ACCELEROMETER_DATA_Z];
LOGD
("ProcessOrientation: Raw acceleration vector: x = %f, y = %f, z = %f,"
"magnitude = %f\n", x, y, z, sqrt(x * x + y * y + z * z));
// Apply a low-pass filter to the acceleration up vector in cartesian space.
// Reset the orientation listener state if the samples are too far apart in
// time or when we see values of (0, 0, 0) which indicates that we polled the
// accelerometer too soon after turning it on and we don't have any data yet.
const long now = event.timestamp();
const long then = mLastFilteredTimestampNanos;
const float timeDeltaMS = (now - then) * 0.000001f;
bool skipSample = false;
if (now < then
|| now > then + MAX_FILTER_DELTA_TIME_NANOS
|| (x == 0 && y == 0 && z == 0)) {
LOGD
("ProcessOrientation: Resetting orientation listener.");
Reset();
skipSample = true;
} else {
const float alpha = timeDeltaMS / (FILTER_TIME_CONSTANT_MS + timeDeltaMS);
x = alpha * (x - mLastFilteredX) + mLastFilteredX;
y = alpha * (y - mLastFilteredY) + mLastFilteredY;
z = alpha * (z - mLastFilteredZ) + mLastFilteredZ;
LOGD
("ProcessOrientation: Filtered acceleration vector: x=%f, y=%f, z=%f,"
"magnitude=%f", z, y, z, sqrt(x * x + y * y + z * z));
skipSample = false;
}
mLastFilteredTimestampNanos = now;
mLastFilteredX = x;
mLastFilteredY = y;
mLastFilteredZ = z;
bool isAccelerating = false;
bool isFlat = false;
bool isSwinging = false;
if (skipSample) {
return -1;
}
// Calculate the magnitude of the acceleration vector.
const float magnitude = sqrt(x * x + y * y + z * z);
if (magnitude < NEAR_ZERO_MAGNITUDE) {
LOGD
("ProcessOrientation: Ignoring sensor data, magnitude too close to"
" zero.");
ClearPredictedRotation();
} else {
// Determine whether the device appears to be undergoing external
// acceleration.
if (this->IsAccelerating(magnitude)) {
isAccelerating = true;
mAccelerationTimestampNanos = now;
}
// Calculate the tilt angle. This is the angle between the up vector and
// the x-y plane (the plane of the screen) in a range of [-90, 90]
// degrees.
// -90 degrees: screen horizontal and facing the ground (overhead)
// 0 degrees: screen vertical
// 90 degrees: screen horizontal and facing the sky (on table)
const int tiltAngle =
static_cast<int>(roundf(asin(z / magnitude) * RADIANS_TO_DEGREES));
AddTiltHistoryEntry(now, tiltAngle);
// Determine whether the device appears to be flat or swinging.
if (this->IsFlat(now)) {
isFlat = true;
mFlatTimestampNanos = now;
}
if (this->IsSwinging(now, tiltAngle)) {
isSwinging = true;
mSwingTimestampNanos = now;
}
// If the tilt angle is too close to horizontal then we cannot determine
// the orientation angle of the screen.
if (abs(tiltAngle) > MAX_TILT) {
LOGD
("ProcessOrientation: Ignoring sensor data, tilt angle too high:"
" tiltAngle=%d", tiltAngle);
ClearPredictedRotation();
} else {
// Calculate the orientation angle.
// This is the angle between the x-y projection of the up vector onto
// the +y-axis, increasing clockwise in a range of [0, 360] degrees.
int orientationAngle =
static_cast<int>(roundf(-atan2f(-x, y) * RADIANS_TO_DEGREES));
if (orientationAngle < 0) {
// atan2 returns [-180, 180]; normalize to [0, 360]
orientationAngle += 360;
}
// Find the nearest rotation.
int nearestRotation = (orientationAngle + 45) / 90;
if (nearestRotation == 4) {
nearestRotation = 0;
}
// Determine the predicted orientation.
if (IsTiltAngleAcceptable(nearestRotation, tiltAngle)
&&
IsOrientationAngleAcceptable
(nearestRotation, orientationAngle, deviceCurrentRotation)) {
UpdatePredictedRotation(now, nearestRotation);
LOGD
("ProcessOrientation: Predicted: tiltAngle=%d, orientationAngle=%d,"
" predictedRotation=%d, predictedRotationAgeMS=%f",
tiltAngle,
orientationAngle,
mPredictedRotation,
((now - mPredictedRotationTimestampNanos) * 0.000001f));
} else {
LOGD
("ProcessOrientation: Ignoring sensor data, no predicted rotation:"
" tiltAngle=%d, orientationAngle=%d",
tiltAngle,
orientationAngle);
ClearPredictedRotation();
}
}
}
// Determine new proposed rotation.
const int oldProposedRotation = mProposedRotation;
if (mPredictedRotation < 0 || IsPredictedRotationAcceptable(now)) {
mProposedRotation = mPredictedRotation;
}
// Write final statistics about where we are in the orientation detection
// process.
LOGD
("ProcessOrientation: Result: oldProposedRotation=%d,currentRotation=%d, "
"proposedRotation=%d, predictedRotation=%d, timeDeltaMS=%f, "
"isAccelerating=%d, isFlat=%d, isSwinging=%d, timeUntilSettledMS=%f, "
"timeUntilAccelerationDelayExpiredMS=%f, timeUntilFlatDelayExpiredMS=%f, "
"timeUntilSwingDelayExpiredMS=%f",
oldProposedRotation,
deviceCurrentRotation, mProposedRotation,
mPredictedRotation, timeDeltaMS, isAccelerating, isFlat,
isSwinging, RemainingMS(now,
mPredictedRotationTimestampNanos +
PROPOSAL_SETTLE_TIME_NANOS),
RemainingMS(now,
mAccelerationTimestampNanos +
PROPOSAL_MIN_TIME_SINCE_ACCELERATION_ENDED_NANOS),
RemainingMS(now,
mFlatTimestampNanos +
PROPOSAL_MIN_TIME_SINCE_FLAT_ENDED_NANOS),
RemainingMS(now,
mSwingTimestampNanos +
PROPOSAL_MIN_TIME_SINCE_SWING_ENDED_NANOS));
// Tell the listener.
if (mProposedRotation != oldProposedRotation && mProposedRotation >= 0) {
LOGD
("ProcessOrientation: Proposed rotation changed! proposedRotation=%d, "
"oldProposedRotation=%d",
mProposedRotation,
oldProposedRotation);
return mProposedRotation;
}
// Don't rotate screen
return -1;
}
bool
ProcessOrientation::IsTiltAngleAcceptable(int rotation, int tiltAngle)
{
return (tiltAngle >= tiltTolerance[rotation][0]
&& tiltAngle <= tiltTolerance[rotation][1]);
}
bool
ProcessOrientation::IsOrientationAngleAcceptable(int rotation,
int orientationAngle,
int currentRotation)
{
// If there is no current rotation, then there is no gap.
// The gap is used only to introduce hysteresis among advertised orientation
// changes to avoid flapping.
if (currentRotation < 0) {
return true;
}
// If the specified rotation is the same or is counter-clockwise adjacent
// to the current rotation, then we set a lower bound on the orientation
// angle. For example, if currentRotation is ROTATION_0 and proposed is
// ROTATION_90, then we want to check orientationAngle > 45 + GAP / 2.
if (rotation == currentRotation || rotation == (currentRotation + 1) % 4) {
int lowerBound = rotation * 90 - 45 + ADJACENT_ORIENTATION_ANGLE_GAP / 2;
if (rotation == 0) {
if (orientationAngle >= 315 && orientationAngle < lowerBound + 360) {
return false;
}
} else {
if (orientationAngle < lowerBound) {
return false;
}
}
}
// If the specified rotation is the same or is clockwise adjacent, then we
// set an upper bound on the orientation angle. For example, if
// currentRotation is ROTATION_0 and rotation is ROTATION_270, then we want
// to check orientationAngle < 315 - GAP / 2.
if (rotation == currentRotation || rotation == (currentRotation + 3) % 4) {
int upperBound = rotation * 90 + 45 - ADJACENT_ORIENTATION_ANGLE_GAP / 2;
if (rotation == 0) {
if (orientationAngle <= 45 && orientationAngle > upperBound) {
return false;
}
} else {
if (orientationAngle > upperBound) {
return false;
}
}
}
return true;
}
bool
ProcessOrientation::IsPredictedRotationAcceptable(long now)
{
// The predicted rotation must have settled long enough.
if (now < mPredictedRotationTimestampNanos + PROPOSAL_SETTLE_TIME_NANOS) {
return false;
}
// The last flat state (time since picked up) must have been sufficiently long
// ago.
if (now < mFlatTimestampNanos + PROPOSAL_MIN_TIME_SINCE_FLAT_ENDED_NANOS) {
return false;
}
// The last swing state (time since last movement to put down) must have been
// sufficiently long ago.
if (now < mSwingTimestampNanos + PROPOSAL_MIN_TIME_SINCE_SWING_ENDED_NANOS) {
return false;
}
// The last acceleration state must have been sufficiently long ago.
if (now < mAccelerationTimestampNanos
+ PROPOSAL_MIN_TIME_SINCE_ACCELERATION_ENDED_NANOS) {
return false;
}
// Looks good!
return true;
}
int
ProcessOrientation::Reset()
{
mLastFilteredTimestampNanos = LONG_MIN;
mProposedRotation = -1;
mFlatTimestampNanos = LONG_MIN;
mSwingTimestampNanos = LONG_MIN;
mAccelerationTimestampNanos = LONG_MIN;
ClearPredictedRotation();
ClearTiltHistory();
return -1;
}
void
ProcessOrientation::ClearPredictedRotation()
{
mPredictedRotation = -1;
mPredictedRotationTimestampNanos = LONG_MIN;
}
void
ProcessOrientation::UpdatePredictedRotation(long now, int rotation)
{
if (mPredictedRotation != rotation) {
mPredictedRotation = rotation;
mPredictedRotationTimestampNanos = now;
}
}
bool
ProcessOrientation::IsAccelerating(float magnitude)
{
return magnitude < MIN_ACCELERATION_MAGNITUDE
|| magnitude > MAX_ACCELERATION_MAGNITUDE;
}
void
ProcessOrientation::ClearTiltHistory()
{
mTiltHistory.history[0].timestampNanos = LONG_MIN;
mTiltHistory.index = 1;
}
void
ProcessOrientation::AddTiltHistoryEntry(long now, float tilt)
{
mTiltHistory.history[mTiltHistory.index].tiltAngle = tilt;
mTiltHistory.history[mTiltHistory.index].timestampNanos = now;
mTiltHistory.index = (mTiltHistory.index + 1) % TILT_HISTORY_SIZE;
mTiltHistory.history[mTiltHistory.index].timestampNanos = LONG_MIN;
}
bool
ProcessOrientation::IsFlat(long now)
{
for (int i = mTiltHistory.index; (i = NextTiltHistoryIndex(i)) >= 0;) {
if (mTiltHistory.history[i].tiltAngle < FLAT_ANGLE) {
break;
}
if (mTiltHistory.history[i].timestampNanos + FLAT_TIME_NANOS <= now) {
// Tilt has remained greater than FLAT_TILT_ANGLE for FLAT_TIME_NANOS.
return true;
}
}
return false;
}
bool
ProcessOrientation::IsSwinging(long now, float tilt)
{
for (int i = mTiltHistory.index; (i = NextTiltHistoryIndex(i)) >= 0;) {
if (mTiltHistory.history[i].timestampNanos + SWING_TIME_NANOS < now) {
break;
}
if (mTiltHistory.history[i].tiltAngle + SWING_AWAY_ANGLE_DELTA <= tilt) {
// Tilted away by SWING_AWAY_ANGLE_DELTA within SWING_TIME_NANOS.
return true;
}
}
return false;
}
int
ProcessOrientation::NextTiltHistoryIndex(int index)
{
index = (index == 0 ? TILT_HISTORY_SIZE : index) - 1;
return mTiltHistory.history[index].timestampNanos != LONG_MIN ? index : -1;
}
float
ProcessOrientation::RemainingMS(long now, long until)
{
return now >= until ? 0 : (until - now) * 0.000001f;
}
} // namespace mozilla
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