Let `--parse/replace-in-metadata` run at any post-processing stage

Closes #5808, #456

README.md

@@ -952,13 +952,18 @@ You can also fork the project on GitHub and run your fork's [build workflow](.gi
                                     mkv/mka video files
     --no-embed-info-json            Do not embed the infojson as an attachment
                                     to the video file
-    --parse-metadata FROM:TO        Parse additional metadata like title/artist
+    --parse-metadata [WHEN:]FROM:TO
+                                    Parse additional metadata like title/artist
                                     from other fields; see "MODIFYING METADATA"
-                                    for details
+                                    for details. Supported values of "WHEN" are
-    --replace-in-metadata FIELDS REGEX REPLACE
+                                    the same as that of --use-postprocessor
+                                    (default: pre_process)
+    --replace-in-metadata [WHEN:]FIELDS REGEX REPLACE
                                     Replace text in a metadata field using the
                                     given regex. This option can be used
-                                    multiple times
+                                    multiple times. Supported values of "WHEN"
+                                    are the same as that of --use-postprocessor
+                                    (default: pre_process)
     --xattrs                        Write metadata to the video file's xattrs
                                     (using dublin core and xdg standards)
     --concat-playlist POLICY        Concatenate videos in a playlist. One of

yt_dlp/__init__.py

@@ -386,10 +386,12 @@ def validate_options(opts):
                 raise ValueError(f'{cmd} is invalid; {err}')
             yield action
 
-    parse_metadata = opts.parse_metadata or []
     if opts.metafromtitle is not None:
-        parse_metadata.append('title:%s' % opts.metafromtitle)
+        opts.parse_metadata.setdefault('pre_process', []).append('title:%s' % opts.metafromtitle)
-    opts.parse_metadata = list(itertools.chain(*map(metadataparser_actions, parse_metadata)))
+    opts.parse_metadata = {
+        k: list(itertools.chain(*map(metadataparser_actions, v)))
+        for k, v in opts.parse_metadata.items()
+    }
 
     # Other options
     if opts.playlist_items is not None:
@@ -561,11 +563,11 @@ def validate_options(opts):
 def get_postprocessors(opts):
     yield from opts.add_postprocessors
 
-    if opts.parse_metadata:
+    for when, actions in opts.parse_metadata.items():
         yield {
             'key': 'MetadataParser',
-            'actions': opts.parse_metadata,
+            'actions': actions,
-            'when': 'pre_process'
+            'when': when
         }
     sponsorblock_query = opts.sponsorblock_mark | opts.sponsorblock_remove
     if sponsorblock_query:

yt_dlp/options.py

@@ -1586,14 +1586,16 @@ def create_parser():
         help=optparse.SUPPRESS_HELP)
     postproc.add_option(
         '--parse-metadata',
-        metavar='FROM:TO', dest='parse_metadata', action='append',
+        metavar='[WHEN:]FROM:TO', dest='parse_metadata', **when_prefix('pre_process'),
         help=(
-            'Parse additional metadata like title/artist from other fields; '
+            'Parse additional metadata like title/artist from other fields; see "MODIFYING METADATA" for details. '
-            'see "MODIFYING METADATA" for details'))
+            'Supported values of "WHEN" are the same as that of --use-postprocessor (default: pre_process)'))
     postproc.add_option(
         '--replace-in-metadata',
-        dest='parse_metadata', metavar='FIELDS REGEX REPLACE', action='append', nargs=3,
+        dest='parse_metadata', metavar='[WHEN:]FIELDS REGEX REPLACE', nargs=3, **when_prefix('pre_process'),
-        help='Replace text in a metadata field using the given regex. This option can be used multiple times')
+        help=(
+            'Replace text in a metadata field using the given regex. This option can be used multiple times. '
+            'Supported values of "WHEN" are the same as that of --use-postprocessor (default: pre_process)'))
     postproc.add_option(
         '--xattrs', '--xattr',
         action='store_true', dest='xattrs', default=False,