Add optional timeout argument to probe

Popen.communicate() supports a timeout argument which is useful in case
there is a risk that the probe hangs.

Author: magnusvmt

ffmpeg/_probe.py

@@ -4,7 +4,7 @@
 from ._utils import convert_kwargs_to_cmd_line_args
 
 
-def probe(filename, cmd='ffprobe', **kwargs):
+def probe(filename, cmd='ffprobe', timeout=None, **kwargs):
     """Run ffprobe on the specified file and return a JSON representation of the output.
 
     Raises:
@@ -18,7 +18,7 @@ def probe(filename, cmd='ffprobe', **kwargs):
     args += [filename]
 
     p = subprocess.Popen(args, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
-    out, err = p.communicate()
+    out, err = p.communicate(timeout=timeout)
     if p.returncode != 0:
         raise Error('ffprobe', out, err)
     return json.loads(out.decode('utf-8'))