+bool Track::empty() const
+{
+ return keys.empty();
+}
+
+int Track::get_num_keys() const
+{
+ return (int)keys.size();
+}
+
+const TrackKey &Track::operator [](int idx) const
+{
+ return keys[idx];
+}
+
+TrackKey &Track::operator [](int idx)
+{
+ return keys[idx];
+}
+
+void Track::set_value(long tm, float val)