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/ModeSelector.h b/media/libheadtracking/ModeSelector.h
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+++ b/media/libheadtracking/ModeSelector.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/HeadTrackingMode.h"
+#include "media/Pose.h"
+
+#include "PoseRateLimiter.h"
+
+namespace android {
+namespace media {
+
+/**
+ * Head-tracking mode selector.
+ *
+ * This class is responsible for production of the determining pose for audio virtualization, based
+ * on a number of available sources and a selectable mode.
+ *
+ * Typical flow is:
+ * ModeSelector selector(...);
+ * while (...) {
+ * // Set inputs.
+ * selector.setFoo(...);
+ * selector.setBar(...);
+ *
+ * // Update outputs based on inputs.
+ * selector.calculate(...);
+ *
+ * // Get outputs.
+ * Pose3f pose = selector.getHeadToStagePose();
+ * }
+ *
+ * This class is not thread-safe, but thread-compatible.
+ *
+ * For details on the frames of reference involved, their composition and the definitions to the
+ * different modes, refer to:
+ * go/immersive-audio-frames
+ *
+ * The actual mode may deviate from the desired mode in the following cases:
+ * - When we cannot get a valid and fresh estimate of the screen-to-head pose, we will fall back
+ * from screen-relative to world-relative.
+ * - When we cannot get a fresh estimate of the world-to-head pose, we will fall back from
+ * world-relative to static.
+ *
+ * All the timestamps used here are of arbitrary units and origin. They just need to be consistent
+ * between all the calls and with the Options provided for determining freshness and rate limiting.
+ */
+class ModeSelector {
+ public:
+ struct Options {
+ int64_t freshnessTimeout = std::numeric_limits<int64_t>::max();
+ };
+
+ ModeSelector(const Options& options, HeadTrackingMode initialMode = HeadTrackingMode::STATIC);
+
+ /** Sets the desired head-tracking mode. */
+ void setDesiredMode(HeadTrackingMode mode);
+
+ /**
+ * Set the screen-to-stage pose, used in all modes.
+ */
+ void setScreenToStagePose(const Pose3f& screenToStage);
+
+ /**
+ * Set the screen-to-head pose, used in screen-relative mode.
+ * The timestamp needs to reflect how fresh the sample is (not necessarily which point in time
+ * it applies to). nullopt can be used if it is determined that the listener is not in front of
+ * the screen.
+ */
+ void setScreenToHeadPose(int64_t timestamp, const std::optional<Pose3f>& screenToHead);
+
+ /**
+ * Set the world-to-head pose, used in world-relative mode.
+ * The timestamp needs to reflect how fresh the sample is (not necessarily which point in time
+ * it applies to).
+ */
+ void setWorldToHeadPose(int64_t timestamp, const Pose3f& worldToHead);
+
+ /**
+ * Process all the previous inputs and update the outputs.
+ */
+ void calculate(int64_t timestamp);
+
+ /**
+ * Get the aggregate head-to-stage pose (primary output of this module).
+ */
+ Pose3f getHeadToStagePose() const;
+
+ /**
+ * Get the actual head-tracking mode (which may deviate from the desired one as mentioned in the
+ * class documentation above).
+ */
+ HeadTrackingMode getActualMode() const;
+
+ private:
+ const Options mOptions;
+
+ HeadTrackingMode mDesiredMode;
+ Pose3f mScreenToStage;
+ std::optional<Pose3f> mScreenToHead;
+ int64_t mScreenToHeadTimestamp;
+ std::optional<Pose3f> mWorldToHead;
+ int64_t mWorldToHeadTimestamp;
+
+ HeadTrackingMode mActualMode;
+ Pose3f mHeadToStage;
+
+ void calculateActualMode(int64_t timestamp);
+};
+
+} // namespace media
+} // namespace android