add public version of ff_read_frame_flush

We need this since we sometimes seek on the
input stream behind ffmpeg's back. After this
all data need to be flushed completely.

libavformat/avformat.h

@@ -2111,6 +2111,11 @@ int av_read_packet(AVFormatContext *s, AVPacket *pkt);
  */
 int av_read_frame(AVFormatContext *s, AVPacket *pkt);
 
+/**
+ * Clear out any buffered data in context
+ */
+void av_read_frame_flush(AVFormatContext *s);
+
 /**
  * Seek to the keyframe at timestamp.
  * 'timestamp' in 'stream_index'.

libavformat/utils.c

@@ -1580,6 +1580,11 @@ void ff_read_frame_flush(AVFormatContext *s)
     }
 }
 
+void av_read_frame_flush(AVFormatContext *s)
+{
+  ff_read_frame_flush(s);
+}
+
 void ff_update_cur_dts(AVFormatContext *s, AVStream *ref_st, int64_t timestamp)
 {
     int i;