diff --git a/src/cdrom.emscripten.c b/src/cdrom.emscripten.c
index 653416c..365fc4f 100644
--- a/src/cdrom.emscripten.c
+++ b/src/cdrom.emscripten.c
@@ -22,8 +22,9 @@
 #include <emscripten.h>
 #include "portab.h"
 #include "cdrom.h"
+#include "nact.h"
 
-int cdrom_getpos_count;
+static int frame_of_getpos = -1;
 
 static int  cdrom_init(char *);
 static int  cdrom_exit();
@@ -62,7 +63,10 @@ int cdrom_stop() {
 }
 
 int cdrom_getPlayingInfo(cd_time *info) {
-	cdrom_getpos_count++;
+	if (nact->frame_count == frame_of_getpos)
+		nact->wait_vsync = TRUE;
+	frame_of_getpos = nact->frame_count;
+
 	int t = EM_ASM_INT_V( return xsystem35.cdPlayer.getPosition(); );
 	info->t = t & 0xff;
 	FRAMES_TO_MSF(t >> 8, &info->m, &info->s, &info->f);
diff --git a/src/nact.c b/src/nact.c
index 63de06f..5530616 100644
--- a/src/nact.c
+++ b/src/nact.c
@@ -183,29 +183,24 @@ static int checkMessage() {
 
 #define MAINLOOP_EVENTCHECK_INTERVAL 16 /* 16 msec */
 
-#ifdef __EMSCRIPTEN__
-
-extern int cdrom_getpos_count;
-
-#endif // __EMSCRIPTEN__
-
 void nact_main() {
 	reset_counter_high(SYSTEMCOUNTER_MSEC, 1, 0);
 	reset_counter_high(SYSTEMCOUNTER_MAINLOOP, MAINLOOP_EVENTCHECK_INTERVAL, 0);
-	int c0;
-	static int cnt = 0;
-	
-#ifdef __EMSCRIPTEN__
-	cdrom_getpos_count = 0;
-#endif
-	while (!nact->is_quit) {
+	int cnt = 0;
 #ifdef ENABLE_SDL
-		nact->input_state = InputNotChecked;
+	nact->frame_count = 0;
+	nact->cmd_count = 0;
+	nact->wait_vsync = FALSE;
 #endif
+	
+	while (!nact->is_quit) {
 		DEBUG_MESSAGE("%d:%x\n", sl_getPage(), sl_getIndex());
 		if (!nact->popupmenu_opened) {
-			c0 = checkMessage();
+			int c0 = checkMessage();
 			check_command(c0);
+#ifdef ENABLE_SDL
+			nact->cmd_count++;
+#endif
 		}
 #ifndef __EMSCRIPTEN__
 		if (!nact->is_message_locked) {
@@ -215,22 +210,15 @@ void nact_main() {
 			}
 		}
 #endif
-		if (cnt == 10000) {
+		if (++cnt == 10000) {
 			Sleep(1); /* XXXX */
 			cnt = 0;
 		}
-		cnt++;
 		nact->callback();
-#ifdef __EMSCRIPTEN__
-		if (cdrom_getpos_count >= 2) {
-			if (!nact->is_message_locked && nact->input_state == InputNotChecked)
-				sys_getInputInfo();
-			WaitVsync();
-			cdrom_getpos_count = 0;
-		}
-#endif
 #ifdef ENABLE_SDL
-		if (nact->input_state == InputCheckMissed) {
+		if (nact->wait_vsync) {
+			nact->frame_count++;
+			nact->wait_vsync = FALSE;
 			WaitVsync();
 		}
 #endif
diff --git a/src/nact.h b/src/nact.h
index 4a67cba..e9f6b1d 100644
--- a/src/nact.h
+++ b/src/nact.h
@@ -143,7 +143,9 @@ typedef struct {
 	} files;
 	
 #ifdef ENABLE_SDL
-	enum { InputNotChecked, InputCheckMissed, HadInput } input_state;
+	int frame_count;
+	int cmd_count;
+	boolean wait_vsync;
 #endif
 
 } NACTINFO;
diff --git a/src/sdl_event.c b/src/sdl_event.c
index 74eb9f0..69edf3d 100644
--- a/src/sdl_event.c
+++ b/src/sdl_event.c
@@ -64,15 +64,14 @@ static int mouse_to_rawkey(int button) {
 
 /* Event処理 */
 static void sdl_getEvent(void) {
+	static int cmd_count_of_prev_input = -1;
 	SDL_Event e;
 	boolean m2b = FALSE, msg_skip = FALSE;
 	int i;
-
-	if (nact->input_state == InputNotChecked)
-		nact->input_state = InputCheckMissed;
+	boolean had_input = false;
 
 	while (SDL_PollEvent(&e)) {
-		nact->input_state = HadInput;
+		had_input = true;
 		switch (e.type) {
 		case SDL_WINDOWEVENT:
 			switch (e.window.event) {
@@ -186,6 +185,11 @@ static void sdl_getEvent(void) {
 			break;
 		}
 	}
+	if (had_input) {
+		cmd_count_of_prev_input = nact->cmd_count;
+	} else if (nact->cmd_count != cmd_count_of_prev_input) {
+		nact->wait_vsync = TRUE;
+	}
 	
 	if (m2b) {
 		menu_open();