OboeAudioService: add thread to service for passing timestamps
Cleanup several TODOs.
Test: test_aaudio in CTS
Change-Id: I7fc956b6a21cbb592f98e1e5a8f43ebd6926d796
Signed-off-by: Phil Burk <philburk@google.com>
diff --git a/services/oboeservice/TimestampScheduler.cpp b/services/oboeservice/TimestampScheduler.cpp
new file mode 100644
index 0000000..17d6c63
--- /dev/null
+++ b/services/oboeservice/TimestampScheduler.cpp
@@ -0,0 +1,44 @@
+/*
+ * Copyright (C) 2016 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.
+ */
+
+// for random()
+#include <stdlib.h>
+
+#include "TimestampScheduler.h"
+
+using namespace oboe;
+
+void TimestampScheduler::start(oboe_nanoseconds_t startTime) {
+ mStartTime = startTime;
+ mLastTime = startTime;
+}
+
+oboe_nanoseconds_t TimestampScheduler::nextAbsoluteTime() {
+ int64_t periodsElapsed = (mLastTime - mStartTime) / mBurstPeriod;
+ // This is an arbitrary schedule that could probably be improved.
+ // It starts out sending a timestamp on every period because we want to
+ // get an accurate picture when the stream starts. Then it slows down
+ // to the occasional timestamps needed to detect a slow drift.
+ int64_t minPeriodsToDelay = (periodsElapsed < 10) ? 1 :
+ (periodsElapsed < 100) ? 3 :
+ (periodsElapsed < 1000) ? 10 : 50;
+ oboe_nanoseconds_t sleepTime = minPeriodsToDelay * mBurstPeriod;
+ // Generate a random rectangular distribution one burst wide so that we get
+ // an uncorrelated sampling of the MMAP pointer.
+ sleepTime += (oboe_nanoseconds_t)(random() * mBurstPeriod / RAND_MAX);
+ mLastTime += sleepTime;
+ return mLastTime;
+}