diff --git a/src/bb/image-io/rt_u3v.h b/src/bb/image-io/rt_u3v.h
index 0cfbcb27..a9ede43e 100644
--- a/src/bb/image-io/rt_u3v.h
+++ b/src/bb/image-io/rt_u3v.h
@@ -781,6 +781,50 @@ class U3V {
         }
     }
 
+    void sync_frame_count(std::vector<ArvBuffer *> &bufs, int timeout_us){
+        uint32_t max_cnt = 0;
+        while (true) {
+            // Update max_cnt
+            for (int i = 0; i < num_sensor_; ++i) {
+                if (max_cnt < devices_[i].frame_count_) {
+                    max_cnt = devices_[i].frame_count_;
+                }
+            }
+
+            // Check all count is same as max_cnt;
+            bool synchronized = true;
+            for (int i = 0; i < num_sensor_; ++i) {
+                synchronized &= devices_[i].frame_count_ == max_cnt;
+            }
+
+            // If it is synchronized, break the loop
+            if (synchronized) {
+                break;
+            }
+
+            // Acquire buffer until cnt is at least max_cnt
+            for (int i = 0; i < devices_.size(); ++i) {
+                while (devices_[i].frame_count_ < max_cnt) {
+                    arv_stream_push_buffer(devices_[i].stream_, bufs[i]);
+                    bufs[i] = arv_stream_timeout_pop_buffer(devices_[i].stream_, timeout_us);
+
+                    if (bufs[i] == nullptr) {
+                        log::error("pop_buffer failed  when sync frame due to timeout ({}s)", timeout_us * 1e-6f);
+                        throw ::std::runtime_error("buffer is null");
+                    }
+                    devices_[i].frame_count_ = frame_count_method_ == FrameCountMethod::TYPESPECIFIC3
+                        ? static_cast<uint32_t>(get_frame_count_from_genDC_descriptor(bufs[i], devices_[i]))
+                        : frame_count_method_ == FrameCountMethod::TIMESTAMP
+                        ? static_cast<uint32_t>(arv_buffer_get_timestamp(bufs[i]) & 0x00000000FFFFFFFF)
+                        : -1;
+                    i == 0 ?
+                        log::trace("All-Popped Frames (USB0, USB1)=({:20}, {:20})", devices_[i].frame_count_, "") :
+                        log::trace("All-Popped Frames (USB0, USB1)=({:20}, {:20})", "", devices_[i].frame_count_);
+                }
+            }
+        }
+    }
+
     g_object_unref_t g_object_unref;
 
     arv_get_major_version_t arv_get_major_version;
@@ -1093,51 +1137,6 @@ class U3VRealCam: public U3V{
         }
     };
 
-
-    void sync_frame_count(std::vector<ArvBuffer *> &bufs, int timeout_us){
-        uint32_t max_cnt = 0;
-        while (true) {
-            // Update max_cnt
-            for (int i = 0; i < num_sensor_; ++i) {
-                if (max_cnt < devices_[i].frame_count_) {
-                    max_cnt = devices_[i].frame_count_;
-                }
-            }
-
-            // Check all count is same as max_cnt;
-            bool synchronized = true;
-            for (int i = 0; i < num_sensor_; ++i) {
-                synchronized &= devices_[i].frame_count_ == max_cnt;
-            }
-
-            // If it is synchronized, break the loop
-            if (synchronized) {
-                break;
-            }
-
-            // Acquire buffer until cnt is at least max_cnt
-            for (int i = 0; i < devices_.size(); ++i) {
-                while (devices_[i].frame_count_ < max_cnt) {
-                    arv_stream_push_buffer(devices_[i].stream_, bufs[i]);
-                    bufs[i] = arv_stream_timeout_pop_buffer(devices_[i].stream_, timeout_us);
-
-                    if (bufs[i] == nullptr) {
-                        log::error("pop_buffer failed  when sync frame due to timeout ({}s)", timeout_us * 1e-6f);
-                        throw ::std::runtime_error("buffer is null");
-                    }
-                    devices_[i].frame_count_ = frame_count_method_ == FrameCountMethod::TYPESPECIFIC3
-                        ? static_cast<uint32_t>(get_frame_count_from_genDC_descriptor(bufs[i], devices_[i]))
-                        : frame_count_method_ == FrameCountMethod::TIMESTAMP
-                        ? static_cast<uint32_t>(arv_buffer_get_timestamp(bufs[i]) & 0x00000000FFFFFFFF)
-                        : -1;
-                    i == 0 ?
-                        log::trace("All-Popped Frames (USB0, USB1)=({:20}, {:20})", devices_[i].frame_count_, "") :
-                        log::trace("All-Popped Frames (USB0, USB1)=({:20}, {:20})", "", devices_[i].frame_count_);
-                }
-            }
-        }
-    }
-
     void consume_old_buffer(std::vector<ArvBuffer *> &bufs, int timeout_us = 3 * 1000 * 1000){
         std::vector<int32_t> N_output_buffers(num_sensor_);
         for (auto i = 0; i < num_sensor_; ++i) {