I think the outer shortcut connection is unnecessary for RRDB. There is already a shortcut connection for Dense blocks, thus the original input is already propagated through the dense blocks. Adding an extra outermost shortcut connection will be equivalent to
where beta is 0.2 in this repo. In other words, the input is scaled by a factor of (1 + beta). When stacking a lot of RRDB blocks, the input grows exponentially (1 + beta)^(n_blocks). Perhaps this is why residual scaling is necessary for ESRGAN?
I think the outer shortcut connection is unnecessary for RRDB. There is already a shortcut connection for Dense blocks, thus the original input is already propagated through the dense blocks. Adding an extra outermost shortcut connection will be equivalent to
where beta is 0.2 in this repo. In other words, the input is scaled by a factor of (1 + beta). When stacking a lot of RRDB blocks, the input grows exponentially (1 + beta)^(n_blocks). Perhaps this is why residual scaling is necessary for ESRGAN?