for f in formats:
# Automatically determine tbr when missing based on abr and vbr (improves
# formats sorting in some cases)
- if 'tbr' not in f and 'abr' in f and 'vbr' in f:
+ if 'tbr' not in f and f.get('abr') is not None and f.get('vbr') is not None:
f['tbr'] = f['abr'] + f['vbr']
def _formats_key(f):