Why the PSNR value decreases by several DBs when I introduces H.264 encoding losses?

[xiaoxiongli]

In my application scenario, the RGB data captured by the camera is down-scale(x2) at the transmit phase, then the down-sampled(x2) image is encoded by H.264 and transmitted over the network, and the H.264 stream are received by the receiver(such as phone or PC), then I do up-scale (x2) by the super-resolution algorithm in the receiver side. My goal is expected that this will save bandwidth for network transmission.

I wanna to use IRN as my down-scale and up-scale algorithm. After using the IRN algorithm to obtain LR images, I use H264 to encode it, but it will introduces some encoding losses. as you know, H264 is not a lossless encoder, and this means y(in below image) has a little change. However, After the H.264 streams are decoded at the receiver and then input to the IRN network for up-scale, the PSNR value decreases by several DBs.

This means during reconstruction of SR image, IRN are Sensitive to the input of the LR( y in below image ), any minor change will result in failure? Is there a way to solve this problem?

[pkuxmq]

For some discussions on this problem please refer to #6.