From b71e15e5b6cf696994282afa1079473bd84d901f Mon Sep 17 00:00:00 2001
From: Katie Pratt <katieannpratt@gmail.com>
Date: Sun, 6 Oct 2019 18:13:39 -0400
Subject: [PATCH] asserting input type and raising TypeError if not valid

---
 youtube_dl/postprocessor/ffmpeg.py | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/youtube_dl/postprocessor/ffmpeg.py b/youtube_dl/postprocessor/ffmpeg.py
index b21dafba9..c7ebd664f 100644
--- a/youtube_dl/postprocessor/ffmpeg.py
+++ b/youtube_dl/postprocessor/ffmpeg.py
@@ -433,7 +433,9 @@ class FFmpegEmbedSubtitlePP(FFmpegPostProcessor):
 class FFmpegMetadataPP(FFmpegPostProcessor):
     def __init__(self, downloader=None, preferredinfo=None):
         super(FFmpegMetadataPP, self).__init__(downloader)
-        self._preferredinfo = preferredinfo if isinstance(preferredinfo, dict) else None
+        if not (isinstance(preferredinfo, dict) or preferredinfo == None):
+            raise TypeError('preferredinfo must be a dictionary, if provided')
+        self._preferredinfo = preferredinfo
 
     def run(self, info):
         metadata = {}