diff --git a/flashvideo/flow_video.py b/flashvideo/flow_video.py
index 3371107..12e48ab 100644
--- a/flashvideo/flow_video.py
+++ b/flashvideo/flow_video.py
@@ -195,6 +195,66 @@ def single_function_evaluation(self,
         print(f'single_function_evaluation time at {t}', end_time - start_time)
         return vt
 
+
+
+
+    def shared_step(self, batch):        
+        x = self.get_input(batch)
+        
+        b, t, c, h, w = x.shape
+        
+        if h*w > (580 * 820) and t > 1: 
+            save_memory_flag = True
+        else:
+            save_memory_flag = False
+                
+        ref_x = batch["ref_mp4"].to(self.dtype)
+                
+        if enable_aug and random.random() < self.share_cache.get("aug_prob", 0.5):
+            # strong pixel deg: ref_x from dataset
+            lr_x = ref_x
+            lr_x = lr_x.permute(0, 2, 1, 3, 4).contiguous()
+                
+        else:
+            # weak pixel deg
+            lr_x = x.reshape(b * t, c, h, w)
+            upscale_factor = self.share_cache.get("upscale_factor", 4)
+            
+
+            if "scale_range" in self.share_cache:
+                scale_range = self.share_cache["scale_range"] # 4 ~ 8              
+                upscale_factor = random.uniform(scale_range[0], scale_range[1])
+            
+            lr_x = F.interpolate(lr_x, scale_factor=1 / upscale_factor, mode="bilinear", align_corners=False, antialias=True)
+            lr_x = F.interpolate(lr_x, size= (h, w) , mode="bilinear", align_corners=False, antialias=True)
+            lr_x = lr_x.reshape(b, t, c, h, w)
+            lr_x = lr_x.permute(0, 2, 1, 3, 4).contiguous()
+        
+        if save_memory_flag:
+            lr_z = self.save_memory_encode_first_stage(lr_x, batch)
+        else:
+            lr_z = self.encode_first_stage(lr_x, batch)
+                 
+                
+            lr_z = lr_z.permute(0, 2, 1, 3, 4).contiguous()
+            self.share_cache["ref_x"] = lr_z
+        
+        x = x.permute(0, 2, 1, 3, 4).contiguous()
+
+        if save_memory_flag:
+            x = self.save_memory_encode_first_stage(x, batch)
+        else:
+            x = self.encode_first_stage(x, batch)
+
+        
+    
+        x = x.permute(0, 2, 1, 3, 4).contiguous()
+                
+        loss, loss_dict = self(x, batch)
+        return loss, loss_dict
+
+
+
     @torch.no_grad()
     def sample(
         self,
@@ -274,5 +334,90 @@ def __init__(self,
         self.schedule = None
         super().__init__(**kwargs)
 
-    def __call__(self, network, denoiser, conditioner, input, batch):
-        pass
+   def __call__(self, network, denoiser, conditioner, input, batch):
+        cond = conditioner(batch)
+        additional_model_inputs = {key: batch[key] for key in self.batch2model_keys.intersection(batch)}
+
+        
+        ref_x = self.share_cache["ref_x"]
+        b, num_f, c, h, w = ref_x.shape
+
+            
+   
+        if "ref_noise_step" in self.share_cache or "ref_noise_step_range" in self.share_cache:
+            if "ref_noise_step" in self.share_cache and "ref_noise_step_range" not in self.share_cache:
+                ref_noise_step = self.share_cache["ref_noise_step"]
+            else:
+                # ref_noise_step_range 600~900 -> 600 ~ 750
+                ref_noise_step_min, ref_noise_step_max = self.share_cache["ref_noise_step_range"]
+                if num_f == 1 and "img_ref_noise_step_range" in self.share_cache:
+                    ref_noise_step_min, ref_noise_step_max = self.share_cache["img_ref_noise_step_range"]
+                local_rank, world_size = dist.get_rank(), dist.get_world_size()
+                local_rand_range = (ref_noise_step_max - ref_noise_step_min) // world_size
+                local_rand_start = local_rank * local_rand_range + ref_noise_step_min
+                local_rand_end = (local_rank + 1) * local_rand_range + ref_noise_step_min
+                ref_noise_step = torch.randint(local_rand_start, local_rand_end, (1,)).item()
+                
+                self.share_cache["sample_ref_noise_step"] = ref_noise_step
+            ref_alphas_cumprod_sqrt =self.sigma_sampler.idx_to_sigma(
+                    torch.zeros(input.shape[0]).fill_(ref_noise_step).long().cpu())
+            
+
+            ref_alphas_cumprod_sqrt = ref_alphas_cumprod_sqrt.to(input.device)
+            ref_x = self.share_cache["ref_x"]
+            ref_noise = torch.randn_like(ref_x)
+            
+            # deg latent
+            ref_noised_input = ref_x * append_dims(ref_alphas_cumprod_sqrt, ref_x.ndim) \
+                    + ref_noise * append_dims(
+            (1 - ref_alphas_cumprod_sqrt**2) ** 0.5, ref_x.ndim
+            )
+            self.share_cache["ref_x"] = ref_noised_input
+      
+            
+        bs = input.shape[0]
+        dev = input.device
+        dtype = input.dtype
+        
+  
+        t = torch.rand(bs, device=dev, dtype=dtype)
+
+
+        if "shift_t" in self.share_cache:
+            shift_t = float(self.share_cache["shift_t"])
+            t = 1 - shift_t*(1-t) / (1 + (shift_t -1)*(1-t))
+
+        num_interval = int(self.share_cache.get("num_noise_interval", 1))
+        # # split t to each device
+        interval = 1.0 / num_interval
+        
+        each_start = [i * interval for i in range(num_interval)]
+        each_start = torch.tensor(each_start, device=dev, dtype=dtype)
+        t = each_start + t * interval
+        
+        dummy_batch_size = num_interval
+
+        
+        idx = 1000 -  (t * 1000)
+        # sample xt and ut
+        x0 = self.share_cache["ref_x"]
+
+        
+        
+        x1 = input
+        x0 = x0.repeat(dummy_batch_size, 1, 1, 1, 1)
+        x1 = x1.repeat(dummy_batch_size, 1, 1, 1, 1)
+        
+        t = pad_v_like_x(t, x0)
+        xt = x0 * (1 - t) + t * x1
+
+        
+        additional_model_inputs["idx"] = idx
+        new_cond = dict()
+        for k, v in cond.items():
+            num_dim = v.ndim
+            new_cond[k] = v.repeat(dummy_batch_size, *([1] * (num_dim - 1)))
+        vt = network(xt, t=idx, c= new_cond, **additional_model_inputs)
+
+    
+        return  (vt - (x1 -x0)).square().mean()
\ No newline at end of file