diff --git a/ptgctl/tools/mock.py b/ptgctl/tools/mock.py
index 6d7cf7c..3b7d45f 100644
--- a/ptgctl/tools/mock.py
+++ b/ptgctl/tools/mock.py
@@ -38,6 +38,7 @@ async def video(api, src=0, pos=0, width=0.3, shape=None, fps=15, speed=1, stepb
     sid = f'{prefix or ""}{sid}'
     if skill:
         api.session.start_recipe(skill)
+    tlast = 0
     async with api.data_push_connect(sid, batch=True) as ws:
         async for im in _video_feed(src, fps, shape, speed=speed):
             if pos:
@@ -48,7 +49,9 @@ async def video(api, src=0, pos=0, width=0.3, shape=None, fps=15, speed=1, stepb
             # print(load(dump_v3(im)))
             if stepbystep:
                 input()
-            await ws.send_data([dump_v3(im)], [sid], [util.format_epoch_time(time.time())])
+            t=time.time()
+            await ws.send_data([dump_v3(im)], [sid], [util.format_epoch_time(t, tlast)])
+            tlast = t
     
 def _img_dump(im, format='jpeg'):
     from PIL import Image
diff --git a/ptgctl/util/__init__.py b/ptgctl/util/__init__.py
index 191ffbf..cb0e1ce 100644
--- a/ptgctl/util/__init__.py
+++ b/ptgctl/util/__init__.py
@@ -51,8 +51,12 @@ def parse_epoch_time(tid: str):
 def format_time(dt: datetime.datetime):
     return format_epoch_time(dt.timestamp())
 
-def format_epoch_time(tid: float):
-    return f'{int(tid * 1000)}-0'
+def format_epoch_time(tid: float, tlast=None):
+    tms = int(tid * 1000)
+    i = 0
+    if tlast and tms == int(tlast * 1000):
+        i = int((tid*1000 - tms)*100)
+    return f'{tms}-{i}'
 
 
 # misc