output/Source: allow the ReplayGainFilter to change the AudioFormat

src/output/Source.cxx

@@ -99,16 +99,21 @@ try {
 	assert(audio_format.IsValid());
 
 	/* the replay_gain filter cannot fail here */
+	if (prepared_other_replay_gain_filter) {
+		other_replay_gain_serial = 0;
+		other_replay_gain_filter =
+			prepared_other_replay_gain_filter->Open(audio_format);
+	}
+
 	if (prepared_replay_gain_filter) {
 		replay_gain_serial = 0;
 		replay_gain_filter =
 			prepared_replay_gain_filter->Open(audio_format);
-	}
 
-	if (prepared_other_replay_gain_filter) {
-		other_replay_gain_serial = 0;
-		other_replay_gain_filter =
-			prepared_other_replay_gain_filter->Open(audio_format);
+		audio_format = replay_gain_filter->GetOutAudioFormat();
+
+		assert(replay_gain_filter->GetOutAudioFormat() ==
+		       other_replay_gain_filter->GetOutAudioFormat());
 	}
 
 	filter = prepared_filter.Open(audio_format);