Solved by InnovArul in post #4 
              
              
                I see. My bad that I didn’t understand it. 
There is still a disadvantage with Conv2d in cases like below: 
Let’s say we have 6 frames with RGB channels. 
With Conv3d, we can emulate applying a conv kernel for every 3 frames to learn short-range temporal features. i.e., with in_channels=3 &  kernel_…