Image encoding and decoding, video encoding and decoding: methods, systems and training methods

A computer implemented method of training a neural network for use in lossy image or video compression, the method comprising:

• (i) receiving an input image;
• (ii) encoding the input image using a first neural network to produce a latent representation, and decoding the latent representation using a second neural network to produce a reconstruction of the input image;
• (iii) producing a first feature map, associated with the input image;
• (iv) producing a second feature map, associated with the reconstruction of the input image;
• (v) evaluating a function based on differences between the first feature map and the second feature map;
• (vi) evaluating a gradient of the function;
• (vii) back-propagating the gradient of the function through the first neural network and the second neural network to update the weights of the first neural network and the second neural network;
• (viii) repeating steps (i) to (vii) to produce a trained first neural network and a trained second neural network.