[fragment] Fix range header when using `-N` and media sequence (#1048)

Authored by: shirt

yt_dlp/downloader/fragment.py

@@ -332,7 +332,7 @@ class FragmentFD(FileDownloader):
 
         def download_fragment(fragment, ctx):
             frag_index = ctx['fragment_index'] = fragment['frag_index']
-            headers = info_dict.get('http_headers', {})
+            headers = info_dict.get('http_headers', {}).copy()
             byte_range = fragment.get('byte_range')
             if byte_range:
                 headers['Range'] = 'bytes=%d-%d' % (byte_range['start'], byte_range['end'] - 1)

yt_dlp/downloader/hls.py

@@ -167,6 +167,7 @@ class HlsFD(FragmentFD):
                         'byte_range': byte_range,
                         'media_sequence': media_sequence,
                     })
+                    media_sequence += 1
 
                 elif line.startswith('#EXT-X-MAP'):
                     if format_index and discontinuity_count != format_index:
@@ -191,6 +192,7 @@ class HlsFD(FragmentFD):
                         'byte_range': byte_range,
                         'media_sequence': media_sequence
                     })
+                    media_sequence += 1
 
                     if map_info.get('BYTERANGE'):
                         splitted_byte_range = map_info.get('BYTERANGE').split('@')