[extractor/common] Use baseURL from f4m manifest for recursive manifest extraction

youtube_dl/extractor/common.py

@@ -891,6 +891,11 @@ class InfoExtractor(object):
         if not media_nodes:
             manifest_version = '2.0'
             media_nodes = manifest.findall('{http://ns.adobe.com/f4m/2.0}media')
+        base_url = xpath_text(
+            manifest, ['{http://ns.adobe.com/f4m/1.0}baseURL', '{http://ns.adobe.com/f4m/2.0}baseURL'],
+            'base URL', default=None)
+        if base_url:
+            base_url = base_url.strip()
         for i, media_el in enumerate(media_nodes):
             if manifest_version == '2.0':
                 media_url = media_el.attrib.get('href') or media_el.attrib.get('url')
@@ -898,7 +903,7 @@ class InfoExtractor(object):
                     continue
                 manifest_url = (
                     media_url if media_url.startswith('http://') or media_url.startswith('https://')
-                    else ('/'.join(manifest_url.split('/')[:-1]) + '/' + media_url))
+                    else ((base_url or '/'.join(manifest_url.split('/')[:-1])) + '/' + media_url))
                 # If media_url is itself a f4m manifest do the recursive extraction
                 # since bitrates in parent manifest (this one) and media_url manifest
                 # may differ leading to inability to resolve the format by requested