SungmanHong:

In N,C,D,H,W… What is D?


D corresponds to the “depth” of the volume, which is the additional dimension spanning the volume besides the height and width.



 SungmanHong:

and why the channels is in the second dimension, not the last dimension?


PyTorch uses the (user-facing) channels-first memory layout by default, so the channel dimension is placed in dim1 (also for 2D layers).