inputs instead of a raw pixels so that's basically the idea in a stack denoising auto-encoder and the hope is that as you keep stacking more layers the higher layers get more more semantics but you should also be careful in thinking about what kind of noise you can add to the features so if back in those days people used to use neural networks with Sigma nonlinearities so in that case it's it's easy to add a noise like masking because Sigma can be considered as you know the neurons firing or not firing but but now