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/PoseDriftCompensator.h b/media/libheadtracking/PoseDriftCompensator.h
new file mode 100644
index 0000000..a71483b
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+++ b/media/libheadtracking/PoseDriftCompensator.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 {
+
+/**
+ * Drift compensator for a stream of poses.
+ *
+ * This is effectively a high-pass filter for a pose stream, removing any DC-offset / bias. The
+ * provided input stream will be "pulled" toward identity with an exponential decay filter with a
+ * configurable time constant. Rotation and translation are handled separately.
+ *
+ * Typical usage:
+ * PoseDriftCompensator comp(...);
+ *
+ * while (...) {
+ * comp.setInput(...);
+ * Pose3f output = comp.getOutput();
+ * }
+ *
+ * There doesn't need to be a 1:1 correspondence between setInput() and getOutput() calls. The
+ * output timestamp is always that of the last setInput() call. Calling recenter() will reset the
+ * bias to the current output, causing the output to be identity.
+ *
+ * The initial bias point is identity.
+ *
+ * This implementation is thread-compatible, but not thread-safe.
+ */
+class PoseDriftCompensator {
+ public:
+ struct Options {
+ float translationalDriftTimeConstant = std::numeric_limits<float>::infinity();
+ float rotationalDriftTimeConstant = std::numeric_limits<float>::infinity();
+ };
+
+ explicit PoseDriftCompensator(const Options& options);
+
+ void setInput(int64_t timestamp, const Pose3f& input);
+
+ void recenter();
+
+ Pose3f getOutput() const;
+
+ private:
+ const Options mOptions;
+
+ Pose3f mPrevInput;
+ Pose3f mOutput;
+ std::optional<int64_t> mTimestamp;
+
+ Pose3f scale(const Pose3f& pose, int64_t dt);
+};
+
+} // namespace media
+} // namespace android