Solved by ptrblck in post #2 
              
              
                nn.PixelShuffle will change the number of output channels as described in the docs: 

Input: (N, L, H_in, W_in) where L= C * upscale_factor**2 
Output: (N, C, H_out, W_out) where H_out = H_in * upscale_factor and W_out = W_in * upscale_factor 

In your case, upscale_factor=2, so the input channels a…