render: implemented frame pool

Optimization

app/widget/viewer/viewer.cpp

@@ -455,7 +455,6 @@ void ViewerWidget::UpdateTextureFromNode()
 
   // Check playback queue for a frame
   if (IsPlaying()) {
-
     // We still run the playback queue even when FrameExistsAtTime returns false because we might be
     // playing backwards and about to start showing frames, so the queue should be prepared for
     // that.

app/widget/viewer/viewerplaybacktimer.cpp

@@ -21,6 +21,7 @@
 #include "viewerplaybacktimer.h"
 
 #include <QDateTime>
+#include <QtMath>
 
 namespace olive {
 
@@ -29,14 +30,14 @@ void ViewerPlaybackTimer::Start(const int64_t &start_timestamp, const int &playb
   start_msec_ = QDateTime::currentMSecsSinceEpoch();
   start_timestamp_ = start_timestamp;
   playback_speed_ = playback_speed;
-  timebase_ = timebase;
+  timebase_ = timebase * 1000;
 }
 
 int64_t ViewerPlaybackTimer::GetTimestampNow() const
 {
   int64_t real_time = QDateTime::currentMSecsSinceEpoch() - start_msec_;
 
-  int64_t frames_since_start = qRound(static_cast<double>(real_time) / (timebase_ * 1000));
+  int64_t frames_since_start = qFloor(static_cast<double>(real_time) / (timebase_));
 
   return start_timestamp_ + frames_since_start * playback_speed_;
 }