+ /**
+ * Frame rate of the stream on the link, or 1/0 if unknown;
+ * if left to 0/0, will be automatically be copied from the first input
+ * of the source filter if it exists.
+ *
+ * Sources should set it to the best estimation of the real frame rate.
+ * Filters should update it if necessary depending on their function.
+ * Sinks can use it to set a default output frame rate.
+ * It is similar to the r_frae_rate field in AVStream.
+ */
+ AVRational frame_rate;
+