[common] use AACL as the default fourcc when AudioTag is 255

youtube_dl/extractor/common.py

@@ -2054,7 +2054,7 @@ class InfoExtractor(object):
             stream_timescale = int_or_none(stream.get('TimeScale')) or timescale
             stream_name = stream.get('Name')
             for track in stream.findall('QualityLevel'):
-                fourcc = track.get('FourCC')
+                fourcc = track.get('FourCC', 'AACL' if track.get('AudioTag') == '255' else None)
                 # TODO: add support for WVC1 and WMAP
                 if fourcc not in ('H264', 'AVC1', 'AACL'):
                     self.report_warning('%s is not a supported codec' % fourcc)