From f8661c6578d2b3cff1e064bc899b6e77c3d92966 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Mike=20F=C3=A4hrmann?= <mike_faehrmann@web.de>
Date: Wed, 13 May 2020 22:35:33 +0200
Subject: [PATCH] [downloader:ytdl] fix file extensions when merging into mkv

---
 gallery_dl/downloader/ytdl.py | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/gallery_dl/downloader/ytdl.py b/gallery_dl/downloader/ytdl.py
index 8e60a0c5..335713f5 100644
--- a/gallery_dl/downloader/ytdl.py
+++ b/gallery_dl/downloader/ytdl.py
@@ -70,6 +70,10 @@ class YoutubeDLDownloader(DownloaderBase):
         if "url" in info_dict:
             text.nameext_from_url(info_dict["url"], pathfmt.kwdict)
 
+        formats = info_dict.get("requested_formats")
+        if formats and not compatible_formats(formats):
+            info_dict["ext"] = "mkv"
+
         if self.outtmpl:
             self.ytdl.params["outtmpl"] = self.outtmpl
             pathfmt.filename = filename = self.ytdl.prepare_filename(info_dict)
@@ -105,4 +109,15 @@ class YoutubeDLDownloader(DownloaderBase):
         return True
 
 
+def compatible_formats(formats):
+    video_ext = formats[0].get("ext")
+    audio_ext = formats[1].get("ext")
+
+    if video_ext == "webm" and audio_ext == "webm":
+        return True
+
+    exts = ("mp3", "mp4", "m4a", "m4p", "m4b", "m4r", "m4v", "ismv", "isma")
+    return video_ext in exts and audio_ext in exts
+
+
 __downloader__ = YoutubeDLDownloader