mp3dec: export replaygain tags from ID3v2

Changelog

@@ -4,6 +4,7 @@ releases are sorted from youngest to oldest.
 version <next>:
 - libx265 encoder
 - shuffleplanes filter
+- replaygain data export
 
 
 version 10:

libavformat/Makefile

@@ -182,7 +182,7 @@ OBJS-$(CONFIG_MOV_DEMUXER)               += mov.o isom.o mov_chan.o
 OBJS-$(CONFIG_MOV_MUXER)                 += movenc.o isom.o avc.o hevc.o \
                                             movenchint.o mov_chan.o
 OBJS-$(CONFIG_MP2_MUXER)                 += mp3enc.o rawenc.o id3v2enc.o
-OBJS-$(CONFIG_MP3_DEMUXER)               += mp3dec.o
+OBJS-$(CONFIG_MP3_DEMUXER)               += mp3dec.o replaygain.o
 OBJS-$(CONFIG_MP3_MUXER)                 += mp3enc.o rawenc.o id3v2enc.o
 OBJS-$(CONFIG_MPC_DEMUXER)               += mpc.o apetag.o img2.o
 OBJS-$(CONFIG_MPC8_DEMUXER)              += mpc8.o apetag.o img2.o

libavformat/mp3dec.c

@@ -27,6 +27,8 @@
 #include "internal.h"
 #include "id3v2.h"
 #include "id3v1.h"
+#include "replaygain.h"
+
 #include "libavcodec/mpegaudiodecheader.h"
 
 #define XING_FLAG_FRAMES 0x01
@@ -194,6 +196,7 @@ static int mp3_read_header(AVFormatContext *s)
 {
     AVStream *st;
     int64_t off;
+    int ret;
 
     st = avformat_new_stream(s, NULL);
     if (!st)
@@ -215,6 +218,10 @@ static int mp3_read_header(AVFormatContext *s)
     if (mp3_parse_vbr_tags(s, st, off) < 0)
         avio_seek(s->pb, off, SEEK_SET);
 
+    ret = ff_replaygain_export(st, s->metadata);
+    if (ret < 0)
+        return ret;
+
     /* the parameters will be extracted from the compressed bitstream */
     return 0;
 }