diff --git a/get_youtube_videos/get_youtube_videos.py b/get_youtube_videos/get_youtube_videos.py
index 9b3ad5b..62b4be3 100644
--- a/get_youtube_videos/get_youtube_videos.py
+++ b/get_youtube_videos/get_youtube_videos.py
@@ -164,14 +164,14 @@ class GetYoutubeVideos:
                             'writesubtitles': True,
                             'writeautomaticsub': True,
                             'writeannotations': True,
-                            'write_all_thumbnails': True,
+                            'write_all_thumbnails': False,
                             'writethumbnail': True,
                             'writeinfojson': True,
                             'subtitlesformat': 'srt',
                             'subtitleslangs': self.config['subtitle_langs'],
                             'allow_multiple_audio_streams': True,
                             'noprogress': True,
-                            'merge_output_format': 'mp4',
+                            'merge_output_format': 'mkv',
                             'format': 'bestvideo+bestaudio[ext=m4a]/best',
                         }
                         with yt_dlp.YoutubeDL(ydl_opts) as ydl: