[youtube] extractor-arg to show live dash formats

If replay is enabled, these formats can be used to download the last 4 hours

README.md

@@ -1381,6 +1381,7 @@ # EXTRACTOR ARGUMENTS
     * `skip`: `hls` or `dash` (or both) to skip download of the respective manifests
     * `player_client`: Clients to extract video data from. The main clients are `web`, `android`, `ios`, `mweb`. These also have `_music`, `_embedded`, `_agegate`, and `_creator` variants (Eg: `web_embedded`) (`mweb` has only `_agegate`). By default, `android,web` is used, but the agegate and creator variants are added as required for age-gated videos. Similarly the music variants are added for `music.youtube.com` urls. You can also use `all` to use all the clients
     * `player_skip`: `configs` - skip any requests for client configs and use defaults
+    * `include_live_dash`: Include live dash formats (These formats don't download properly)
     * `comment_sort`: `top` or `new` (default) - choose comment sorting mode (on YouTube's side).
     * `max_comments`: maximum amount of comments to download (default all).
     * `max_comment_depth`: maximum depth for nested comments. YouTube supports depths 1 or 2 (default). 

yt_dlp/extractor/youtube.py

@@ -2628,7 +2628,9 @@ def _extract_formats(self, streaming_data, video_id, player_url, is_live):
             yield dct
 
         skip_manifests = self._configuration_arg('skip')
-        get_dash = not is_live and 'dash' not in skip_manifests and self.get_param('youtube_include_dash_manifest', True)
+        get_dash = (
+            (not is_live or self._configuration_arg('include_live_dash'))
+            and 'dash' not in skip_manifests and self.get_param('youtube_include_dash_manifest', True))
         get_hls = 'hls' not in skip_manifests and self.get_param('youtube_include_hls_manifest', True)
 
         def guess_quality(f):
@@ -3458,7 +3460,7 @@ class YoutubeTabIE(YoutubeBaseInfoExtractor):
     }, {
         'url': 'https://www.youtube.com/channel/UCoMdktPbSTixAyNGwb-UYkQ/live',
         'info_dict': {
-            'id': 'FMtPN8yp5LU',  # This will keep changing
+            'id': '3yImotZU3tw',  # This will keep changing
             'ext': 'mp4',
             'title': compat_str,
             'uploader': 'Sky News',

yt_dlp/options.py

@@ -1367,7 +1367,7 @@ def _dict_from_options_callback(
         '--no-hls-split-discontinuity',
         dest='hls_split_discontinuity', action='store_false',
         help='Do not split HLS playlists to different formats at discontinuities such as ad breaks (default)')
-    _extractor_arg_parser = lambda key, vals='': (key.strip().lower(), [val.strip() for val in vals.split(',')])
+    _extractor_arg_parser = lambda key, vals='': (key.strip().lower().replace('-', '_'), [val.strip() for val in vals.split(',')])
     extractor.add_option(
         '--extractor-args',
         metavar='KEY:ARGS', dest='extractor_args', default={}, type='str',