[FFmpegFixupM3u8PP] Check audio codec before fixup (#6778)

Closes #6673
Authored by: bashonly

yt_dlp/postprocessor/ffmpeg.py

@@ -898,8 +898,11 @@ class FFmpegFixupM3u8PP(FFmpegFixupPostProcessor):
     @PostProcessor._restrict_to(images=False)
     def run(self, info):
         if all(self._needs_fixup(info)):
+            args = ['-f', 'mp4']
+            if self.get_audio_codec(info['filepath']) == 'aac':
+                args.extend(['-bsf:a', 'aac_adtstoasc'])
             self._fixup('Fixing MPEG-TS in MP4 container', info['filepath'], [
-                *self.stream_copy_opts(), '-f', 'mp4', '-bsf:a', 'aac_adtstoasc'])
+                *self.stream_copy_opts(), *args])
         return [], info