[utils] Improve subtitles_filename (closes #22753)

4 files changed, 13 insertions, 7 deletions

diff --git a/test/test_utils.py b/test/test_utils.py
index 659c6ece5..3920542bb 100644
--- a/test/test_utils.py
+++ b/test/test_utils.py
@@ -74,6 +74,7 @@ from youtube_dl.utils import (
     str_to_int,
     strip_jsonp,
     strip_or_none,
+    subtitles_filename,
     timeconvert,
     unescapeHTML,
     unified_strdate,
@@ -261,6 +262,11 @@ class TestUtil(unittest.TestCase):
         self.assertEqual(replace_extension('.abc', 'temp'), '.abc.temp')
         self.assertEqual(replace_extension('.abc.ext', 'temp'), '.abc.temp')
 
+    def test_subtitles_filename(self):
+        self.assertEqual(subtitles_filename('abc.ext', 'en', 'vtt'), 'abc.en.vtt')
+        self.assertEqual(subtitles_filename('abc.ext', 'en', 'vtt', 'ext'), 'abc.en.vtt')
+        self.assertEqual(subtitles_filename('abc.unexpected_ext', 'en', 'vtt', 'ext'), 'abc.unexpected_ext.en.vtt')
+
     def test_remove_start(self):
         self.assertEqual(remove_start(None, 'A - '), None)
         self.assertEqual(remove_start('A - B', 'A - '), 'B')
diff --git a/youtube_dl/YoutubeDL.py b/youtube_dl/YoutubeDL.py
index c3d1407f9..f5cb46308 100755
--- a/youtube_dl/YoutubeDL.py
+++ b/youtube_dl/YoutubeDL.py
@@ -1814,7 +1814,7 @@ class YoutubeDL(object):
             ie = self.get_info_extractor(info_dict['extractor_key'])
             for sub_lang, sub_info in subtitles.items():
                 sub_format = sub_info['ext']
-                sub_filename = subtitles_filename(filename, sub_lang, sub_format)
+                sub_filename = subtitles_filename(filename, sub_lang, sub_format, info_dict.get('ext'))
                 if self.params.get('nooverwrites', False) and os.path.exists(encodeFilename(sub_filename)):
                     self.to_screen('[info] Video subtitle %s.%s is already present' % (sub_lang, sub_format))
                 else:
diff --git a/youtube_dl/postprocessor/ffmpeg.py b/youtube_dl/postprocessor/ffmpeg.py
index 70416c25e..fd3f921a8 100644
--- a/youtube_dl/postprocessor/ffmpeg.py
+++ b/youtube_dl/postprocessor/ffmpeg.py
@@ -393,7 +393,7 @@ class FFmpegEmbedSubtitlePP(FFmpegPostProcessor):
             sub_ext = sub_info['ext']
             if ext != 'webm' or ext == 'webm' and sub_ext == 'vtt':
                 sub_langs.append(lang)
-                sub_filenames.append(subtitles_filename(filename, lang, sub_ext))
+                sub_filenames.append(subtitles_filename(filename, lang, sub_ext, ext))
             else:
                 if not webm_vtt_warn and ext == 'webm' and sub_ext != 'vtt':
                     webm_vtt_warn = True
@@ -606,9 +606,9 @@ class FFmpegSubtitlesConvertorPP(FFmpegPostProcessor):
                 self._downloader.to_screen(
                     '[ffmpeg] Subtitle file for %s is already in the requested format' % new_ext)
                 continue
-            old_file = subtitles_filename(filename, lang, ext)
+            old_file = subtitles_filename(filename, lang, ext, info.get('ext'))
             sub_filenames.append(old_file)
-            new_file = subtitles_filename(filename, lang, new_ext)
+            new_file = subtitles_filename(filename, lang, new_ext, info.get('ext'))
 
             if ext in ('dfxp', 'ttml', 'tt'):
                 self._downloader.report_warning(
@@ -616,7 +616,7 @@ class FFmpegSubtitlesConvertorPP(FFmpegPostProcessor):
                     'which results in style information loss')
 
                 dfxp_file = old_file
-                srt_file = subtitles_filename(filename, lang, 'srt')
+                srt_file = subtitles_filename(filename, lang, 'srt', info.get('ext'))
 
                 with open(dfxp_file, 'rb') as f:
                     srt_data = dfxp2srt(f.read())
diff --git a/youtube_dl/utils.py b/youtube_dl/utils.py
index 798757241..53117ea90 100644
--- a/youtube_dl/utils.py
+++ b/youtube_dl/utils.py
@@ -2906,8 +2906,8 @@ def determine_ext(url, default_ext='unknown_video'):
         return default_ext
 
 
-def subtitles_filename(filename, sub_lang, sub_format):
-    return filename.rsplit('.', 1)[0] + '.' + sub_lang + '.' + sub_format
+def subtitles_filename(filename, sub_lang, sub_format, expected_real_ext=None):
+    return replace_extension(filename, sub_lang + '.' + sub_format, expected_real_ext)
 
 
 def date_from_str(date_str):