diff --git a/audio_render/AudioRender.dll b/audio_render/AudioRender.dll
index af1e722..6487ba6 100644
Binary files a/audio_render/AudioRender.dll and b/audio_render/AudioRender.dll differ
diff --git a/audio_render/AudioRender.pdb b/audio_render/AudioRender.pdb
index c23b0e1..e87a60d 100644
Binary files a/audio_render/AudioRender.pdb and b/audio_render/AudioRender.pdb differ
diff --git a/utils/__init__.py b/utils/__init__.py
index 7240263..dc67ac2 100644
--- a/utils/__init__.py
+++ b/utils/__init__.py
@@ -1,3 +1,4 @@
 #encoding = utf8
 
 from .async_task_queue import AsyncTaskQueue
+from .utils import mirror_index
diff --git a/utils/utils.py b/utils/utils.py
new file mode 100644
index 0000000..5297afb
--- /dev/null
+++ b/utils/utils.py
@@ -0,0 +1,10 @@
+#encoding = utf8
+
+def mirror_index(size, index):
+    # size = len(self.coord_list_cycle)
+    turn = index // size
+    res = index % size
+    if turn % 2 == 0:
+        return res
+    else:
+        return size - res - 1
\ No newline at end of file