flush on answer for inbound only

src/switch_channel.c

@@ -3263,6 +3263,7 @@ SWITCH_DECLARE(switch_status_t) switch_channel_perform_pre_answer(switch_channel
 
 	if (status == SWITCH_STATUS_SUCCESS) {
 		switch_channel_perform_mark_pre_answered(channel, file, func, line);
+		switch_channel_audio_sync(channel);
 	} else {
 		switch_channel_hangup(channel, SWITCH_CAUSE_INCOMPATIBLE_DESTINATION);
 	}
@@ -3535,6 +3536,9 @@ SWITCH_DECLARE(switch_status_t) switch_channel_perform_answer(switch_channel_t *
 
 	if (status == SWITCH_STATUS_SUCCESS) {
 		switch_channel_perform_mark_answered(channel, file, func, line);
+		if (!switch_channel_test_flag(channel, CF_EARLY_MEDIA)) {
+			switch_channel_audio_sync(channel);
+		}
 	} else {
 		switch_channel_hangup(channel, SWITCH_CAUSE_INCOMPATIBLE_DESTINATION);
 	}