diff --git a/src/decoder/plugins/FfmpegMetaData.cxx b/src/decoder/plugins/FfmpegMetaData.cxx
index 75c06c282..316c85481 100644
--- a/src/decoder/plugins/FfmpegMetaData.cxx
+++ b/src/decoder/plugins/FfmpegMetaData.cxx
@@ -30,8 +30,15 @@ extern "C" {
 #include <libavutil/dict.h>
 }
 
+/**
+ * FFmpeg specific tag name mappings, as supported by
+ * libavformat/id3v2.c, libavformat/mov.c and others.
+ */
 static constexpr struct tag_table ffmpeg_tags[] = {
+	/* from libavformat/id3v2.c, libavformat/mov.c */
 	{ "album_artist", TAG_ALBUM_ARTIST },
+
+	/* from libavformat/mov.c */
 	{ "sort_album_artist", TAG_ALBUM_ARTIST_SORT },
 	{ "sort_artist", TAG_ARTIST_SORT },