[ffmpeg] check for - file name in _ffmpeg_filename_argument

youtube_dl/downloader/external.py

@@ -235,9 +235,6 @@ class FFmpegFD(ExternalFD):
             args += ['-f', EXT_TO_OUT_FORMATS.get(info_dict['ext'], info_dict['ext'])]
 
         args = [encodeArgument(opt) for opt in args]
-        if tmpfilename == '-':
-            args.append('pipe:1')
-        else:
         args.append(encodeFilename(ffpp._ffmpeg_filename_argument(tmpfilename), True))
 
         self._debug_cmd(args)

youtube_dl/postprocessor/ffmpeg.py

@@ -175,7 +175,7 @@ class FFmpegPostProcessor(PostProcessor):
         # Always use 'file:' because the filename may contain ':' (ffmpeg
         # interprets that as a protocol) or can start with '-' (-- is broken in
         # ffmpeg, see https://ffmpeg.org/trac/ffmpeg/ticket/2127 for details)
-        return 'file:' + fn
+        return 'file:' + fn if fn != '-' else fn
 
 
 class FFmpegExtractAudioPP(FFmpegPostProcessor):