[postprocessor/ffmpeg] Fix avconv processing broken in #19025 (closes #19067)

youtube_dl/postprocessor/ffmpeg.py

@@ -217,9 +217,11 @@ class FFmpegPostProcessor(PostProcessor):
                 encodeArgument('-i'),
                 encodeFilename(self._ffmpeg_filename_argument(path), True)
             ])
-        cmd = ([encodeFilename(self.executable, True), encodeArgument('-y')] +
+        cmd = [encodeFilename(self.executable, True), encodeArgument('-y')]
-               [encodeArgument('-loglevel'), encodeArgument('repeat+info')] +
+        # avconv does not have repeat option
-               files_cmd +
+        if self.basename == 'ffmpeg':
+            cmd += [encodeArgument('-loglevel'), encodeArgument('repeat+info')]
+        cmd += (files_cmd +
                 [encodeArgument(o) for o in opts] +
                 [encodeFilename(self._ffmpeg_filename_argument(out_path), True)])