Arduino controlled video switch
In general, to get completely seamless switching among live video sources, you need to make sure the sources are frame-synchronized. In a studio, this is accomplished by having all sources (cameras, playback machines) synchronized to a common master clock. If your sources are synchronized and you're dealing with analog video signals, then the analog switches you've suggested might work.

In other situations, when the sources can't be synchronized, a frame buffer can be used to time-align one source with another. But this is not the sort of thing you're going to find in a single chip.