[extractor/youtube] More metadata for storyboards (#4334)

Authored by: ftk

yt_dlp/extractor/common.py

@@ -383,6 +383,10 @@ class InfoExtractor:
     section_start:  Start time of the section in seconds
     section_end:    End time of the section in seconds
 
+    The following fields should only be set for storyboards:
+    rows:           Number of rows in each storyboard fragment, as an integer
+    columns:        Number of columns in each storyboard fragment, as an integer
+
     Unless mentioned otherwise, the fields should be Unicode strings.
 
     Unless mentioned otherwise, None is equivalent to absence of information.

yt_dlp/extractor/youtube.py

@@ -3340,6 +3340,9 @@ def _extract_storyboard(self, player_responses, duration):
                 'url': url,
                 'width': width,
                 'height': height,
+                'fps': frame_count / duration,
+                'rows': rows,
+                'columns': cols,
                 'fragments': [{
                     'url': url.replace('$M', str(j)),
                     'duration': min(fragment_duration, duration - (j * fragment_duration)),