Bobingstern:

I don’t know how to find out the dimensions of the images (which are just arrays)


Once you’ve created the tensor you can check its shape via print(tensor.shape). Depending how you’ve created this particular tensor (from a dataset or DataLoader) it would have 3 or 4 dimensions. A DataLoader will create a batch of samples, so it would have 4 dimensions in the shape [batch_size, channels, height, width].



 Bobingstern:

how to make a conv layer for stacked frames.


Based on your description it seems you are dealing with images with 4 channels, so the first conv layer should be created via in_channels=4.