84 lines
2.6 KiB
C
84 lines
2.6 KiB
C
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/*
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* Copyright (C) 2022 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#pragma once
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#include <cstdint>
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namespace android::audioflinger {
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/**
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* MonotonicFrameCounter
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*
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* Advances a monotonic frame count based on input timestamp pairs (frames, time).
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* It takes into account a possible flush, which will "reset" the frames to 0.
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*
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* This class is used to drive VolumeShaper volume automation.
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*
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* The timestamps provided in updateAndGetMonotonicFrameCount should
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* be of sufficient granularity for the purpose at hand. Currently no temporal
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* extrapolation is done.
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*
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* This class is not thread safe.
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*/
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class MonotonicFrameCounter {
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public:
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/**
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* Receives a new timestamp pair (frames, time) and returns a monotonic frameCount.
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*
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* \param newFrameCount the frameCount currently played.
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* \param newTime the time corresponding to the frameCount.
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* \return a monotonic frame count usable for automation timing.
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*/
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int64_t updateAndGetMonotonicFrameCount(int64_t newFrameCount, int64_t newTime);
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/**
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* Notifies when a flush occurs, whereupon the received frameCount sequence restarts at 0.
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*
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* \return the last reported frameCount.
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*/
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int64_t onFlush();
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/**
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* Returns the received (input) frameCount to reported (output) frameCount offset.
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*
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* This offset is sufficient to ensure monotonicity after flush is called,
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* suitability for any other purpose is *not* guaranteed.
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*/
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int64_t getOffsetFrameCount() const { return mOffsetFrameCount; }
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/**
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* Returns the last received frameCount.
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*/
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int64_t getLastReceivedFrameCount() const {
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return mLastReceivedFrameCount;
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}
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/**
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* Returns the last reported frameCount from updateAndGetMonotonicFrameCount().
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*/
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int64_t getLastReportedFrameCount() const {
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// This is consistent after onFlush().
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return mOffsetFrameCount + mLastReceivedFrameCount;
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}
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private:
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int64_t mOffsetFrameCount = 0;
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int64_t mLastReceivedFrameCount = 0;
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};
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} // namespace android::audioflinger
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