diff -urN midi_prog-/midtxt.c midi_prog/midtxt.c
--- midi_prog-/midtxt.c	2015-05-11 00:00:00.000000000 +0900
+++ midi_prog/midtxt.c	2015-06-05 00:00:00.000000000 +0900
@@ -221,6 +221,40 @@
 }
 
 int
+tx_abs_conv(void)
+{
+	char buf[1024], tmp[1024];
+	int abs = 0, delta;
+
+	while(fgets(buf, sizeof(buf), stdin)){
+		if(sscanf(buf, "delta=%d ", &delta) == 1){
+			strcpy(tmp, strchr(buf, ' '));
+			abs += delta;
+			sprintf(buf, "abs=%08d%s", abs, tmp);
+		}
+		fputs(buf, stdout);
+	}
+	return 0;
+}
+
+int
+tx_delta_conv(void)
+{
+	char buf[1024], tmp[1024];
+	int abs_prev = 0, abs;
+
+	while(fgets(buf, sizeof(buf), stdin)){
+		if(sscanf(buf, "abs=%08d ", &abs) == 1){
+			strcpy(tmp, strchr(buf, ' '));
+			sprintf(buf, "delta=%d%s", abs - abs_prev, tmp);
+			abs_prev = abs;
+		}
+		fputs(buf, stdout);
+	}
+	return 0;
+}
+
+int
 main(int ac, char **av)
 {
 	char buf_cmd[16], buf_type[16], buf_meta[16], buf[256];
@@ -228,6 +262,8 @@
 	int v, hi, low, same, ch, note, velo, type, n, i;
 
 	if(opt_idx("-r", ac, av) >= 0) return rconv();
+	if(opt_idx("-tx_abs", ac, av) >= 0) return tx_abs_conv();
+	if(opt_idx("-tx_delta", ac, av) >= 0) return tx_delta_conv();
 
 	rd_str(4, buf);
 	printf("%s\n", buf);