[postprocessor/EmbedThumbnail,postprocessor/FFmpegMetadata] Fix error on attaching thumbnails and info json for mkv/mka (#6647)

Authored by: Lesmiscore

Current yt-dlp code never hit this bug, but would hit once filename sanitization gets better

yt_dlp/postprocessor/embedthumbnail.py

@@ -107,7 +107,7 @@ class EmbedThumbnailPP(FFmpegPostProcessor):
                 options.extend(['-map', '-0:%d' % old_stream])
                 new_stream -= 1
             options.extend([
-                '-attach', thumbnail_filename,
+                '-attach', self._ffmpeg_filename_argument(thumbnail_filename),
                 '-metadata:s:%d' % new_stream, 'mimetype=%s' % mimetype,
                 '-metadata:s:%d' % new_stream, 'filename=cover.%s' % thumbnail_ext])
 

yt_dlp/postprocessor/ffmpeg.py

@@ -809,7 +809,7 @@ class FFmpegMetadataPP(FFmpegPostProcessor):
             new_stream -= 1
 
         yield (
-            '-attach', infofn,
+            '-attach', self._ffmpeg_filename_argument(infofn),
             f'-metadata:s:{new_stream}', 'mimetype=application/json',
             f'-metadata:s:{new_stream}', 'filename=info.json',
         )