*/
void avfilter_formats_unref(AVFilterFormats **ref);
+int avfilter_poll_frame(AVFilterLink *link);
+
/**
* A filter pad used for either input or output
*/
void (*draw_slice)(AVFilterLink *link, int y, int height);
/**
+ * Frame poll callback. This returns the number of immediately available
+ * frames. It should return a positive value if the next request_frame()
+ * is guaranteed to return one frame (with no delay).
+ *
+ * Defaults to just calling the source poll_frame() method.
+ *
+ * Output video pads only.
+ */
+ int (*poll_frame)(AVFilterLink *link);
+
+ /**
* Frame request callback. A call to this should result in at least one
* frame being output over the given link. This should return zero on
* success, and another value on error.