Head-tracking library for Immersive Audio
See README.md for details.
Bug: 188502620
Test: atest --host libheadtracking-test
Change-Id: I34201c4780e5e581cc96449bd89863bcbc250783
diff --git a/media/libheadtracking/PoseRateLimiter.h b/media/libheadtracking/PoseRateLimiter.h
new file mode 100644
index 0000000..aa2fe80
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+++ b/media/libheadtracking/PoseRateLimiter.h
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+/*
+ * Copyright (C) 2021 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.
+ */
+#pragma once
+
+#include <optional>
+
+#include "media/Pose.h"
+
+namespace android {
+namespace media {
+
+/**
+ * Limits a stream of poses to a given maximum translational and rotational velocities.
+ *
+ * Normal operation:
+ *
+ * Pose3f output;
+ * PoseRateLimiter limiter(...);
+ *
+ * // Limiting is disabled. Output will be the same as last input.
+ * limiter.setTarget(...);
+ * output = limiter.calculatePose(...);
+ * limiter.setTarget(...);
+ * output = limiter.calculatePose(...);
+ *
+ * // Enable limiting. Output will no longer be necessarily the same as last input.
+ * limiter.enable();
+ * limiter.setTarget(...);
+ * output = limiter.calculatePose(...);
+ * limiter.setTarget(...);
+ * output = limiter.calculatePose(...);
+ *
+ * // When eventually the output has been able to catch up with the last input, the limited will be
+ * // automatically disabled again and the output will match the input again.
+ * limiter.setTarget(...);
+ * output = limiter.calculatePose(...);
+ *
+ * As shown above, the limiter is turned on manually via enable(), but turns off automatically as
+ * soon as the output is able to catch up to the input. The intention is that rate limiting will be
+ * turned on at specific times to smooth out any artificial discontinuities introduced to the pose
+ * stream, but the rest of the time will be a simple passthrough.
+
+ * setTarget(...) and calculatePose(...) don't have to be ordered in any particular way. However,
+ * setTarget or reset() must be called at least once prior to the first calculatePose().
+ *
+ * Calling reset() instead of setTarget() forces the output to the given pose and disables rate
+ * limiting.
+ *
+ * This implementation is thread-compatible, but not thread-safe.
+ */
+class PoseRateLimiter {
+ public:
+ struct Options {
+ float maxTranslationalVelocity = std::numeric_limits<float>::infinity();
+ float maxRotationalVelocity = std::numeric_limits<float>::infinity();
+ };
+
+ explicit PoseRateLimiter(const Options& options);
+
+ void enable();
+
+ void reset(const Pose3f& target);
+ void setTarget(const Pose3f& target);
+
+ Pose3f calculatePose(int64_t timestamp);
+
+ private:
+ struct Point {
+ Pose3f pose;
+ int64_t timestamp;
+ };
+
+ const Options mOptions;
+ bool mLimiting;
+ std::optional<Pose3f> mTargetPose;
+ std::optional<Point> mOutput;
+};
+
+} // namespace media
+} // namespace android