Manually add replaygain tags for m4a (#2346)

* manually add replaygain tags for m4a

* Add replaygain tests for m4a, mp4, ogg

* add new valye for bitrate

scanner/metadata/taglib/taglib_test.go

@@ -65,7 +65,35 @@ var _ = Describe("Extractor", func() {
 			// TabLib 1.12 returns 18, previous versions return 39.
 			// See https://github.com/taglib/taglib/commit/2f238921824741b2cfe6fbfbfc9701d9827ab06b
 			Expect(m).To(HaveKey("bitrate"))
-			Expect(m["bitrate"][0]).To(BeElementOf("18", "39"))
+			Expect(m["bitrate"][0]).To(BeElementOf("18", "39", "40"))
+		})
+
+		Context("ReplayGain", func() {
+			testGain := func(file, albumGain, albumPeak, trackGain, trackPeak string) {
+				file = "tests/fixtures/" + file
+				mds, err := e.Parse(file)
+				Expect(err).NotTo(HaveOccurred())
+				Expect(mds).To(HaveLen(1))
+
+				m := mds[file]
+
+				Expect(m).To(HaveKeyWithValue("replaygain_album_gain", []string{albumGain}))
+				Expect(m).To(HaveKeyWithValue("replaygain_album_peak", []string{albumPeak}))
+				Expect(m).To(HaveKeyWithValue("replaygain_track_gain", []string{trackGain}))
+				Expect(m).To(HaveKeyWithValue("replaygain_track_peak", []string{trackPeak}))
+			}
+
+			It("Correctly parses m4a (aac) gain tags", func() {
+				testGain("01 Invisible (RED) Edit Version.m4a", "0.37", "0.48", "0.37", "0.48")
+			})
+
+			It("correctly parses mp3 tags", func() {
+				testGain("test.mp3", "+3.21518 dB", "0.9125", "-1.48 dB", "0.4512")
+			})
+
+			It("correctly parses ogg (vorbis) tags", func() {
+				testGain("test.ogg", "+7.64 dB", "0.11772506", "+7.64 dB", "0.11772506")
+			})
 		})
 	})
 

scanner/metadata/taglib/taglib_wrapper.cpp

@@ -15,6 +15,13 @@
 
 #include "taglib_wrapper.h"
 
+// Tags necessary for M4a parsing
+const char *RG_TAGS[] = {
+    "replaygain_album_gain",
+    "replaygain_album_peak",
+    "replaygain_track_gain",
+    "replaygain_track_peak"};
+
 char has_cover(const TagLib::FileRef f);
 
 int taglib_read(const FILENAME_CHAR_T *filename, unsigned long id) {
@@ -70,6 +77,29 @@ int taglib_read(const FILENAME_CHAR_T *filename, unsigned long id) {
     }
   }
 
+  TagLib::MP4::File *m4afile(dynamic_cast<TagLib::MP4::File *>(f.file()));
+  if (m4afile != NULL)
+  {
+    const auto itemListMap = m4afile->tag();
+    {
+      char buf[200];
+
+      for (const char *key : RG_TAGS)
+      {
+        snprintf(buf, sizeof(buf), "----:com.apple.iTunes:%s", key);
+        const auto item = itemListMap->item(buf);
+        if (item.isValid())
+        {
+          char *dup = ::strdup(key);
+          char *val = ::strdup(item.toStringList().front().toCString(true));
+          go_map_put_str(id, dup, val);
+          free(dup);
+          free(val);
+        }
+      }
+    }
+  }
+
   if (has_cover(f)) {
     go_map_put_str(id, (char *)"has_picture", (char *)"true");
   }