From 0fd32b36ad2b364f074ad71a23a8fd18dc84116d Mon Sep 17 00:00:00 2001
From: Stephen Birarda <commit@birarda.com>
Date: Fri, 15 Apr 2016 11:04:35 -0700
Subject: [PATCH] use a steadier clock for AudioMixer block timing

---
 assignment-client/src/audio/AudioMixer.cpp | 27 ++++++++++++----------
 1 file changed, 15 insertions(+), 12 deletions(-)

diff --git a/assignment-client/src/audio/AudioMixer.cpp b/assignment-client/src/audio/AudioMixer.cpp
index cc6c4930ff..7f8b44e8b2 100644
--- a/assignment-client/src/audio/AudioMixer.cpp
+++ b/assignment-client/src/audio/AudioMixer.cpp
@@ -19,6 +19,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <thread>
 
 #ifdef _WIN32
 #include <math.h>
@@ -577,15 +578,14 @@ void AudioMixer::domainSettingsRequestComplete() {
 void AudioMixer::broadcastMixes() {
     auto nodeList = DependencyManager::get<NodeList>();
 
-    int64_t nextFrame = 0;
-    QElapsedTimer timer;
-    timer.start();
-
-    int64_t usecToSleep = AudioConstants::NETWORK_FRAME_USECS;
+    auto nextFrameTimestamp = p_high_resolution_clock::now();
+    auto timeToSleep = std::chrono::microseconds(0);
 
     const int TRAILING_AVERAGE_FRAMES = 100;
     int framesSinceCutoffEvent = TRAILING_AVERAGE_FRAMES;
 
+    int currentFrame { 1 };
+
     while (!_isFinished) {
         const float STRUGGLE_TRIGGER_SLEEP_PERCENTAGE_THRESHOLD = 0.10f;
         const float BACK_OFF_TRIGGER_SLEEP_PERCENTAGE_THRESHOLD = 0.20f;
@@ -595,12 +595,12 @@ void AudioMixer::broadcastMixes() {
         const float CURRENT_FRAME_RATIO = 1.0f / TRAILING_AVERAGE_FRAMES;
         const float PREVIOUS_FRAMES_RATIO = 1.0f - CURRENT_FRAME_RATIO;
 
-        if (usecToSleep < 0) {
-            usecToSleep = 0;
+        if (timeToSleep.count() < 0) {
+            timeToSleep = std::chrono::microseconds(0);
         }
 
         _trailingSleepRatio = (PREVIOUS_FRAMES_RATIO * _trailingSleepRatio)
-            + (usecToSleep * CURRENT_FRAME_RATIO / (float) AudioConstants::NETWORK_FRAME_USECS);
+            + (timeToSleep.count() * CURRENT_FRAME_RATIO / (float) AudioConstants::NETWORK_FRAME_USECS);
 
         float lastCutoffRatio = _performanceThrottlingRatio;
         bool hasRatioChanged = false;
@@ -718,11 +718,14 @@ void AudioMixer::broadcastMixes() {
             break;
         }
 
-        usecToSleep = (++nextFrame * AudioConstants::NETWORK_FRAME_USECS) - (timer.nsecsElapsed() / 1000);
+        // push the next frame timestamp to when we should send the next
+        nextFrameTimestamp += std::chrono::microseconds(AudioConstants::NETWORK_FRAME_USECS);
 
-        if (usecToSleep > 0) {
-            usleep(usecToSleep);
-        }
+        // sleep as long as we need until next frame, if we can
+        auto now = p_high_resolution_clock::now();
+        timeToSleep = std::chrono::duration_cast<std::chrono::microseconds>(nextFrameTimestamp - now);
+
+        std::this_thread::sleep_for(timeToSleep);
     }
 }