README.md

@@ -1379,12 +1379,11 @@ Available for the media that is a track or a part of a music album:
  - `track` (string): Title of the track
  - `track_number` (numeric): Number of the track within an album or a disc
  - `track_id` (string): Id of the track
- - `artists` (list): Artist(s) of the track
- - `composers` (list): Composer(s) of the piece
- - `genres` (list): Genre(s) of the track
+ - `artist` (string): Artist(s) of the track
+ - `genre` (string): Genre(s) of the track
  - `album` (string): Title of the album the track belongs to
  - `album_type` (string): Type of the album
- - `album_artists` (list): List of all artists appeared on the album
+ - `album_artist` (string): List of all artists appeared on the album
  - `disc_number` (numeric): Number of the disc or other physical medium the track belongs to
 
 Available only when using `--download-sections` and for `chapter:` prefix when using `--split-chapters` for videos with internal chapters:
@@ -1762,11 +1761,10 @@ Metadata fields            | From
 `description`,  `synopsis` | `description`
 `purl`, `comment`          | `webpage_url`
 `track`                    | `track_number`
-`artist`                   | `artists`, `creator`, `uploader` or `uploader_id`
-`composer`                 | `composers`
-`genre`                    | `genres`
+`artist`                   | `artist`, `creator`, `uploader` or `uploader_id`
+`genre`                    | `genre`
 `album`                    | `album`
-`album_artist`             | `album_artists`
+`album_artist`             | `album_artist`
 `disc`                     | `disc_number`
 `show`                     | `series`
 `season_number`            | `season_number`

yt_dlp/YoutubeDL.py

@@ -24,6 +24,7 @@ import traceback
 import unicodedata
 
 from .cache import Cache
+
 from .compat import functools, urllib  # isort: split
 from .compat import compat_os_name, compat_shlex_quote, urllib_req_to_req
 from .cookies import LenientSimpleCookie, load_cookies
@@ -3928,10 +3929,9 @@ class YoutubeDL:
 
         # These imports can be slow. So import them only as needed
         from .extractor.extractors import _LAZY_LOADER
-        from .extractor.extractors import (
-            _PLUGIN_CLASSES as plugin_ies,
+        from .extractor.extractors import _PLUGIN_CLASSES as plugin_ies
+        from .extractor.extractors import \
             _PLUGIN_OVERRIDES as plugin_ie_overrides
-        )
 
         def get_encoding(stream):
             ret = str(getattr(stream, 'encoding', 'missing (%s)' % type(stream).__name__))

yt_dlp/__init__.py

@@ -670,6 +670,11 @@ def get_postprocessors(opts):
             'add_metadata': opts.addmetadata,
             'add_infojson': opts.embed_infojson,
         }
+    # MutagenMetadata must run after FFmpegMetadata
+    if opts.addmetadata:
+        yield {
+            'key': 'MutagenMetadata',
+        }
     # Deprecated
     # This should be above EmbedThumbnail since sponskrub removes the thumbnail attachment
     # but must be below EmbedSubtitle and FFmpegMetadata

yt_dlp/extractor/common.py

@@ -423,7 +423,7 @@ class InfoExtractor:
     track_id:       Id of the track (useful in case of custom indexing, e.g. 6.iii),
                     as a unicode string.
     artists:        List of artists of the track.
-    composers:      List of composers of the piece.
+    composers:      List of composers of the piece
     genres:         List of genres of the track.
     album:          Title of the album the track belongs to.
     album_type:     Type of the album (e.g. "Demo", "Full-length", "Split", "Compilation", etc).

yt_dlp/postprocessor/__init__.py

@@ -30,6 +30,7 @@ from .metadataparser import (
 )
 from .modify_chapters import ModifyChaptersPP
 from .movefilesafterdownload import MoveFilesAfterDownloadPP
+from .mutagenmetadata import MutagenMetadataPP
 from .sponskrub import SponSkrubPP
 from .sponsorblock import SponsorBlockPP
 from .xattrpp import XAttrMetadataPP

yt_dlp/postprocessor/mutagenmetadata.py

@@ -0,0 +1,42 @@
+from .common import PostProcessor
+from ..dependencies import mutagen
+
+if mutagen:
+    from mutagen.easymp4 import EasyMP4
+    from mutagen.flac import FLAC
+    from mutagen.mp3 import EasyMP3
+    from mutagen.musepack import Musepack
+    from mutagen.oggopus import OggOpus
+    from mutagen.oggvorbis import OggVorbis
+
+
+class MutagenMetadataPP(PostProcessor):
+    def __init__(self, downloader):
+        PostProcessor.__init__(self, downloader)
+
+    @PostProcessor._restrict_to(images=False)
+    def run(self, information):
+        extension = information['ext']
+        ret = [], information
+        if not mutagen:
+            if extension in ['mp3', 'm4a', 'ogg', 'opus', 'flac', '.mpc']:
+                self.report_warning('module mutagen was not found. Tags with multiple values (e.g. artist, album artist and genre) may be set incorrectly. Please install using `python -m pip install mutagen`')
+            return ret
+        tag_mapping = {
+            'artist': 'artists',
+            'albumartist': 'album_artists',
+            'genre': 'genres',
+            'composer': 'composers'
+        }
+        supported_formats = [EasyMP3, EasyMP4, OggVorbis, OggOpus, FLAC, Musepack]
+        file = mutagen.File(information['filepath'], supported_formats)
+        if not file:
+            return ret
+        if isinstance(file, EasyMP4):
+            file.RegisterTextKey('composer', '\251wrt')
+        for tag_key, info_key in tag_mapping.items():
+            value = information.get(info_key)
+            if value:
+                file[tag_key] = value
+        file.save()
+        return ret