Improve URL extraction

youtube_dl/extractor/firsttv.py

@@ -10,6 +10,7 @@ from ..utils import (
     int_or_none,
     qualities,
     unified_strdate,
+    url_or_none,
 )
 
 
@@ -88,8 +89,8 @@ class FirstTVIE(InfoExtractor):
             formats = []
             path = None
             for f in item.get('mbr', []):
-                src = f.get('src')
-                if not src or not isinstance(src, compat_str):
+                src = url_or_none(f.get('src'))
+                if not src:
                     continue
                 tbr = int_or_none(self._search_regex(
                     r'_(\d{3,})\.mp4', src, 'tbr', default=None))