avformat: split muxing functions from util.c

libavformat/Makefile

@@ -12,6 +12,7 @@ OBJS = allformats.o         \
        id3v1.o              \
        id3v2.o              \
        metadata.o           \
+       mux.o                \
        options.o            \
        os_support.o         \
        riff.o               \

libavformat/internal.h

@@ -345,4 +345,13 @@ int ff_read_packet(AVFormatContext *s, AVPacket *pkt);
 int ff_interleave_packet_per_dts(AVFormatContext *s, AVPacket *out,
                                  AVPacket *pkt, int flush);
 
+/**
+ * Return the frame duration in seconds. Return 0 if not available.
+ */
+void ff_compute_frame_duration(int *pnum, int *pden, AVStream *st,
+                               AVCodecParserContext *pc, AVPacket *pkt);
+
+int ff_get_audio_frame_size(AVCodecContext *enc, int size, int mux);
+
+
 #endif /* AVFORMAT_INTERNAL_H */