I am trying to get accustomed to using sub-streams. Previously I had avoided using them. Why does it seem that my Dahua cameras look the same on the live-view after enabling the 640x480 substream but the Hikvision looks different? Clearly 640x480 is a 4:3 proportion, but it seems that I only see this on the Hikvision (multi-camera grid-live-view.) Why?