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/*
* Copyright 2018 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 "oboe/LatencyTuner.h"
using namespace oboe;
LatencyTuner::LatencyTuner(AudioStream &stream)
: mStream(stream) {
reset();
}
Result LatencyTuner::tune() {
if (mState == State::Unsupported) {
return Result::ErrorUnimplemented;
}
Result result = Result::OK;
// Process reset requests.
int32_t numRequests = mLatencyTriggerRequests.load();
if (numRequests != mLatencyTriggerResponses.load()) {
mLatencyTriggerResponses.store(numRequests);
reset();
}
// Set state to Active if the idle countdown has reached zero.
if (mState == State::Idle && --mIdleCountDown <= 0) {
mState = State::Active;
}
// When state is Active attempt to change the buffer size if the number of xRuns has increased.
if (mState == State::Active) {
auto xRunCountResult = mStream.getXRunCount();
if (xRunCountResult == Result::OK) {
if ((xRunCountResult.value() - mPreviousXRuns) > 0) {
mPreviousXRuns = xRunCountResult.value();
int32_t oldBufferSize = mStream.getBufferSizeInFrames();
int32_t requestedBufferSize = oldBufferSize + mStream.getFramesPerBurst();
auto setBufferResult = mStream.setBufferSizeInFrames(requestedBufferSize);
if (setBufferResult != Result::OK) {
result = setBufferResult;
mState = State::Unsupported;
} else if (setBufferResult.value() == oldBufferSize) {
mState = State::AtMax;
}
}
} else {
mState = State::Unsupported;
}
}
if (mState == State::Unsupported) {
result = Result::ErrorUnimplemented;
}
if (mState == State::AtMax) {
result = Result::OK;
}
return result;
}
void LatencyTuner::requestReset() {
if (mState != State::Unsupported) {
mLatencyTriggerRequests++;
}
}
void LatencyTuner::reset() {
mState = State::Idle;
mIdleCountDown = kIdleCount;
// Set to minimal latency
mStream.setBufferSizeInFrames(mStream.getFramesPerBurst());
}
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