Question 1: Short answer
mediumAI-checkedAutoencoders & VAEsA convolutional autoencoder's encoder is:
x = F.relu(nn.Conv2d(1, 16, 3, padding=1)(x)) # input: 1 × 28 × 28
x = nn.MaxPool2d(2, 2)(x)
x = F.relu(nn.Conv2d(16, 4, 3, padding=1)(x))
x = nn.MaxPool2d(2, 2)(x) # compressed representation
How many numbers does the compressed representation of one image contain?