audio input name isn't necessarily a file

--- src/transcode.c.orig	Wed Jan  6 01:12:40 2010
+++ src/transcode.c	Wed Jan  6 01:13:06 2010
@@ -1213,9 +1213,11 @@ static void setup_input_sources(vob_t *vob)
         /* we always have at least one source */
         tc_next_audio_in_file(vob);
     }
+#if 0
     if (!validate_source_path(vob->audio_in_file)) {
         tc_error("invalid input audio file: %s", vob->audio_in_file);
     }
+#endif
 }
 
 static void teardown_input_sources(vob_t *vob)