added rational type

CMakeLists.txt

@@ -193,6 +193,8 @@ set(OLIVE_SOURCES
   global/math.h
   global/path.cpp
   global/path.h
+  global/rational.h
+  global/rational.cpp
   global/timing.cpp
   global/timing.h
   nodes/inputs/boolinput.cpp

global/rational.cpp

@@ -0,0 +1,2 @@
+#include "rational.h"
+

global/rational.h

@@ -0,0 +1,14 @@
+#ifndef RATIONAL_H
+#define RATIONAL_H
+
+#include <libavformat/avformat.h>
+
+namespace olive {
+  /**
+   * Rational type for timeline values. Currently we just use FFmpeg's AVRational for ease but we can change this
+   * later if we want.
+   */
+  using rational = AVRational;
+};
+
+#endif // RATIONAL_H