[YoutubeDL] Allow filtering by string properties (#4906)

youtube_dl/YoutubeDL.py

@@ -832,9 +832,7 @@ class YoutubeDL(object):
             \]$
             ''' % '|'.join(map(re.escape, OPERATORS.keys())))
         m = operator_rex.search(format_spec)
-        if not m:
+        if m:
-            raise ValueError('Invalid format specification %r' % format_spec)
-
             try:
                 comparison_value = int(m.group('value'))
             except ValueError:
@@ -847,6 +845,25 @@ class YoutubeDL(object):
                             m.group('value'), format_spec))
             op = OPERATORS[m.group('op')]
 
+        if not m:
+            STR_OPERATORS = {
+                '=': operator.eq,
+                '!=': operator.ne,
+            }
+            str_operator_rex = re.compile(r'''(?x)\s*\[
+                \s*(?P<key>ext|acodec|vcodec|container|protocol)
+                \s*(?P<op>%s)(?P<none_inclusive>\s*\?)?
+                \s*(?P<value>[a-zA-Z0-9_-]+)
+                \s*\]$
+                ''' % '|'.join(map(re.escape, STR_OPERATORS.keys())))
+            m = str_operator_rex.search(format_spec)
+            if m:
+                comparison_value = m.group('value')
+                op = STR_OPERATORS[m.group('op')]
+
+        if not m:
+            raise ValueError('Invalid format specification %r' % format_spec)
+
         def _filter(f):
             actual_value = f.get(m.group('key'))
             if actual_value is None: