flacdec: export replaygain tags from Vorbis comments

Signed-off-by: Anton Khirnov <anton@khirnov.net>

libavformat/Makefile

@@ -116,6 +116,7 @@ OBJS-$(CONFIG_FILMSTRIP_MUXER)           += filmstripenc.o
 OBJS-$(CONFIG_FLAC_DEMUXER)              += flacdec.o rawdec.o \
                                             flac_picture.o   \
                                             oggparsevorbis.o \
+                                            replaygain.o     \
                                             vorbiscomment.o
 OBJS-$(CONFIG_FLAC_MUXER)                += flacenc.o flacenc_header.o \
                                             vorbiscomment.o

libavformat/flacdec.c

@@ -26,6 +26,7 @@
 #include "rawdec.h"
 #include "oggdec.h"
 #include "vorbiscomment.h"
+#include "replaygain.h"
 #include "libavcodec/bytestream.h"
 
 static int flac_read_header(AVFormatContext *s)
@@ -146,6 +147,10 @@ static int flac_read_header(AVFormatContext *s)
         }
     }
 
+    ret = ff_replaygain_export(st, s->metadata);
+    if (ret < 0)
+        return ret;
+
     return 0;
 }