Why the train_h and val_h is different?

[zhaozhongch]

Just confused in CamVid.py, it has the following code

h, w      = 720, 960
train_h   = int(h * 2 / 3)  # 480
train_w   = int(w * 2 / 3)  # 640
val_h     = int(h/32) * 32  # 704
val_w     = w               # 960

Why the training height and validation height has a different size and both of them are different from the original image size? What's the magic to make the network output image has a pixel to pixel corresponding to the 720*960 image?