1dec33abe3739b2116ef6fbac36f7ca5d26f9d190Phil Burk/* 2dec33abe3739b2116ef6fbac36f7ca5d26f9d190Phil Burk * Copyright (C) 2016 The Android Open Source Project 3dec33abe3739b2116ef6fbac36f7ca5d26f9d190Phil Burk * 4dec33abe3739b2116ef6fbac36f7ca5d26f9d190Phil Burk * Licensed under the Apache License, Version 2.0 (the "License"); 5dec33abe3739b2116ef6fbac36f7ca5d26f9d190Phil Burk * you may not use this file except in compliance with the License. 6dec33abe3739b2116ef6fbac36f7ca5d26f9d190Phil Burk * You may obtain a copy of the License at 7dec33abe3739b2116ef6fbac36f7ca5d26f9d190Phil Burk * 8dec33abe3739b2116ef6fbac36f7ca5d26f9d190Phil Burk * http://www.apache.org/licenses/LICENSE-2.0 9dec33abe3739b2116ef6fbac36f7ca5d26f9d190Phil Burk * 10dec33abe3739b2116ef6fbac36f7ca5d26f9d190Phil Burk * Unless required by applicable law or agreed to in writing, software 11dec33abe3739b2116ef6fbac36f7ca5d26f9d190Phil Burk * distributed under the License is distributed on an "AS IS" BASIS, 12dec33abe3739b2116ef6fbac36f7ca5d26f9d190Phil Burk * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13dec33abe3739b2116ef6fbac36f7ca5d26f9d190Phil Burk * See the License for the specific language governing permissions and 14dec33abe3739b2116ef6fbac36f7ca5d26f9d190Phil Burk * limitations under the License. 15dec33abe3739b2116ef6fbac36f7ca5d26f9d190Phil Burk */ 16dec33abe3739b2116ef6fbac36f7ca5d26f9d190Phil Burk 17dec33abe3739b2116ef6fbac36f7ca5d26f9d190Phil Burk// for random() 18dec33abe3739b2116ef6fbac36f7ca5d26f9d190Phil Burk#include <stdlib.h> 19dec33abe3739b2116ef6fbac36f7ca5d26f9d190Phil Burk 20dec33abe3739b2116ef6fbac36f7ca5d26f9d190Phil Burk#include "TimestampScheduler.h" 21dec33abe3739b2116ef6fbac36f7ca5d26f9d190Phil Burk 225ed503c7a66c90f93759c90237a9b432dbd93f9fPhil Burkusing namespace aaudio; 23dec33abe3739b2116ef6fbac36f7ca5d26f9d190Phil Burk 243316d5e6d375a4f09c681205e9094d30a0bfc4a2Phil Burkvoid TimestampScheduler::start(int64_t startTime) { 25dec33abe3739b2116ef6fbac36f7ca5d26f9d190Phil Burk mStartTime = startTime; 26dec33abe3739b2116ef6fbac36f7ca5d26f9d190Phil Burk mLastTime = startTime; 27dec33abe3739b2116ef6fbac36f7ca5d26f9d190Phil Burk} 28dec33abe3739b2116ef6fbac36f7ca5d26f9d190Phil Burk 293316d5e6d375a4f09c681205e9094d30a0bfc4a2Phil Burkint64_t TimestampScheduler::nextAbsoluteTime() { 30dec33abe3739b2116ef6fbac36f7ca5d26f9d190Phil Burk int64_t periodsElapsed = (mLastTime - mStartTime) / mBurstPeriod; 31dec33abe3739b2116ef6fbac36f7ca5d26f9d190Phil Burk // This is an arbitrary schedule that could probably be improved. 32dec33abe3739b2116ef6fbac36f7ca5d26f9d190Phil Burk // It starts out sending a timestamp on every period because we want to 33dec33abe3739b2116ef6fbac36f7ca5d26f9d190Phil Burk // get an accurate picture when the stream starts. Then it slows down 34dec33abe3739b2116ef6fbac36f7ca5d26f9d190Phil Burk // to the occasional timestamps needed to detect a slow drift. 35dec33abe3739b2116ef6fbac36f7ca5d26f9d190Phil Burk int64_t minPeriodsToDelay = (periodsElapsed < 10) ? 1 : 36dec33abe3739b2116ef6fbac36f7ca5d26f9d190Phil Burk (periodsElapsed < 100) ? 3 : 37dec33abe3739b2116ef6fbac36f7ca5d26f9d190Phil Burk (periodsElapsed < 1000) ? 10 : 50; 383316d5e6d375a4f09c681205e9094d30a0bfc4a2Phil Burk int64_t sleepTime = minPeriodsToDelay * mBurstPeriod; 39dec33abe3739b2116ef6fbac36f7ca5d26f9d190Phil Burk // Generate a random rectangular distribution one burst wide so that we get 40dec33abe3739b2116ef6fbac36f7ca5d26f9d190Phil Burk // an uncorrelated sampling of the MMAP pointer. 413316d5e6d375a4f09c681205e9094d30a0bfc4a2Phil Burk sleepTime += (int64_t)(random() * mBurstPeriod / RAND_MAX); 42dec33abe3739b2116ef6fbac36f7ca5d26f9d190Phil Burk mLastTime += sleepTime; 43dec33abe3739b2116ef6fbac36f7ca5d26f9d190Phil Burk return mLastTime; 44dec33abe3739b2116ef6fbac36f7ca5d26f9d190Phil Burk} 45