diff --git a/main.c b/main.c
index 7fb0d78..eccd4fe 100644
--- a/main.c
+++ b/main.c
@@ -21,6 +21,8 @@ int process() {
     struct fb_var_screeninfo vinfo;
     struct fb_fix_screeninfo finfo;
 
+    uint16_t *screenbuf[3];
+    uint8_t bufNum = 0;
 
     bcm_host_init();
 
@@ -61,6 +63,15 @@ int process() {
         return -1;
     }
 
+    screenbuf[0] = (uint16_t *)malloc(vinfo.xres * vinfo.yres * 2 * 3);
+    if(!screenbuf[0]) {
+        printf("malloc fail");
+        return -1;
+    }
+    memset(screenbuf[0], 0, vinfo.xres * vinfo.yres * 2 * 2);
+    screenbuf[1] = &screenbuf[0][vinfo.xres * vinfo.yres];
+    screenbuf[2] = &screenbuf[1][vinfo.xres * vinfo.yres];
+
     fbp = (char*) mmap(0, finfo.smem_len, PROT_READ | PROT_WRITE, MAP_SHARED, fbfd, 0);
     if (fbp <= 0) {
         syslog(LOG_ERR, "Unable to create mamory mapping");
@@ -74,8 +85,54 @@ int process() {
 
     while (1) {
         ret = vc_dispmanx_snapshot(display, screen_resource, 0);
-        vc_dispmanx_resource_read_data(screen_resource, &rect1, fbp, vinfo.xres * vinfo.bits_per_pixel / 8);
-        usleep(25 * 1000);
+        // Transfer snamshot to screenbuf
+        vc_dispmanx_resource_read_data(screen_resource, &rect1,
+          (char *)screenbuf[bufNum], vinfo.xres * vinfo.bits_per_pixel / 8);
+        // Calculate delta between two screenbufs
+        for(int i=0; i<vinfo.xres * vinfo.yres; i++) {
+          screenbuf[2][i] = screenbuf[0][i] ^ screenbuf[1][i];
+        }
+        // Find bounding rect of nonzero pixels
+        uint32_t first, last;
+
+        // Find first nonzero word
+        for(first=0; (first < (vinfo.xres * vinfo.yres)) &&
+          !screenbuf[2][first]; first++);
+
+        if(first < (vinfo.xres * vinfo.yres)) {
+          // Find last nonzero word
+          for(last=vinfo.xres * vinfo.yres - 1; (last > first) &&
+            !screenbuf[2][last]; last--);
+
+          int firstRow = first / vinfo.xres;
+          int lastRow  = last / vinfo.xres;
+          // printf("%d %d\n", firstRow, lastRow);
+
+          int firstCol = vinfo.xres - 1, lastCol = 0;
+          for(int row=firstRow; row <= lastRow; row++) {
+            uint16_t *s = &screenbuf[2][row * vinfo.xres];
+            for(int col=0; col<vinfo.xres; col++) {
+              if(s[col]) {
+                if(col < firstCol) firstCol = col;
+                if(col > lastCol)  lastCol  = col;
+              }
+            }
+          }
+          // printf("(%d,%d) (%d,%d)\n", firstCol, firstRow, lastCol, lastRow);
+
+          int width = lastCol - firstCol + 1;
+          uint16_t *src, *dst;
+          src = &screenbuf[bufNum][firstRow * vinfo.xres + firstCol];
+          dst = (uint16_t *)&fbp[(firstRow * vinfo.xres + firstCol) * 2];
+          for(int row=firstRow; row <= lastRow; row++) {
+            memcpy(dst, src, width * 2);
+            src += vinfo.xres;
+            dst += vinfo.xres;
+          }
+//          memcpy(fbp, screenbuf[2], vinfo.xres * vinfo.yres * 2);
+          bufNum = 1 - bufNum;
+        }
+        usleep(1000000 / 60);
     }
 
     munmap(fbp, finfo.smem_len);
diff --git a/main.c.orig b/main.c.orig
new file mode 100644
index 0000000..7fb0d78
--- /dev/null
+++ b/main.c.orig
@@ -0,0 +1,95 @@
+
+#include <stdio.h>
+#include <syslog.h>
+#include <fcntl.h>
+#include <linux/fb.h>
+#include <sys/mman.h>
+
+#include <bcm_host.h>
+
+int process() {
+    DISPMANX_DISPLAY_HANDLE_T display;
+    DISPMANX_MODEINFO_T display_info;
+    DISPMANX_RESOURCE_HANDLE_T screen_resource;
+    VC_IMAGE_TRANSFORM_T transform;
+    uint32_t image_prt;
+    VC_RECT_T rect1;
+    int ret;
+    int fbfd = 0;
+    char *fbp = 0;
+
+    struct fb_var_screeninfo vinfo;
+    struct fb_fix_screeninfo finfo;
+
+
+    bcm_host_init();
+
+    display = vc_dispmanx_display_open(0);
+    if (!display) {
+        syslog(LOG_ERR, "Unable to open primary display");
+        return -1;
+    }
+    ret = vc_dispmanx_display_get_info(display, &display_info);
+    if (ret) {
+        syslog(LOG_ERR, "Unable to get primary display information");
+        return -1;
+    }
+    syslog(LOG_INFO, "Primary display is %d x %d", display_info.width, display_info.height);
+
+
+    fbfd = open("/dev/fb1", O_RDWR);
+    if (fbfd == -1) {
+        syslog(LOG_ERR, "Unable to open secondary display");
+        return -1;
+    }
+    if (ioctl(fbfd, FBIOGET_FSCREENINFO, &finfo)) {
+        syslog(LOG_ERR, "Unable to get secondary display information");
+        return -1;
+    }
+    if (ioctl(fbfd, FBIOGET_VSCREENINFO, &vinfo)) {
+        syslog(LOG_ERR, "Unable to get secondary display information");
+        return -1;
+    }
+
+    syslog(LOG_INFO, "Second display is %d x %d %dbps\n", vinfo.xres, vinfo.yres, vinfo.bits_per_pixel);
+
+    screen_resource = vc_dispmanx_resource_create(VC_IMAGE_RGB565, vinfo.xres, vinfo.yres, &image_prt);
+    if (!screen_resource) {
+        syslog(LOG_ERR, "Unable to create screen buffer");
+        close(fbfd);
+        vc_dispmanx_display_close(display);
+        return -1;
+    }
+
+    fbp = (char*) mmap(0, finfo.smem_len, PROT_READ | PROT_WRITE, MAP_SHARED, fbfd, 0);
+    if (fbp <= 0) {
+        syslog(LOG_ERR, "Unable to create mamory mapping");
+        close(fbfd);
+        ret = vc_dispmanx_resource_delete(screen_resource);
+        vc_dispmanx_display_close(display);
+        return -1;
+    }
+
+    vc_dispmanx_rect_set(&rect1, 0, 0, vinfo.xres, vinfo.yres);
+
+    while (1) {
+        ret = vc_dispmanx_snapshot(display, screen_resource, 0);
+        vc_dispmanx_resource_read_data(screen_resource, &rect1, fbp, vinfo.xres * vinfo.bits_per_pixel / 8);
+        usleep(25 * 1000);
+    }
+
+    munmap(fbp, finfo.smem_len);
+    close(fbfd);
+    ret = vc_dispmanx_resource_delete(screen_resource);
+    vc_dispmanx_display_close(display);
+}
+
+int main(int argc, char **argv) {
+    setlogmask(LOG_UPTO(LOG_DEBUG));
+    openlog("fbcp", LOG_NDELAY | LOG_PID, LOG_USER);
+
+    return process();
+}
+
+
+