Photoshop Extended tries to maintain a link between the source video file and video layer even when you modify or move the video footage outside Photoshop. If, for some reason, the link is broken between the video layer and the referenced source file, the Replace Footage command lets you relink the video layer to the source video file. The Replace Footage command can also replace the video or image sequence frames in a video layer with frames from a different video or image sequence source.

Photoshop tries to maintain the link between the video layer and the source file even if you move or rename the video source. However, if moving, renaming, or deleting a video source file breaks the link between it and the video layer, an alert icon  appears on that layer in the Layers palette. You can use the Replace Footage command to relink the video layer to the source file.