Direct manipulation of video is one of the more uncanny HCI concepts I’ve ever seen. Instead of manipulating time with a traditional scrubber bar, the user can drag objects in the video across their path of movement. Nothing in the video actually changes, but the perception is that you can directly manipulate the objects in the video stream by pulling them around through time.
There’s a Windows application called DimP which implements this interface. When you hover over a movable object in the video, a light path appears that emphasizes the object’s motion curve, which you can then move the object across. From the DimP website:
So what’s being manipulated, exactly? Both the video content (e.g., the things you see moving in the video) and the “tape head”. When using DimP, the user directly manipulates the video content and indirectly manipulates the tape head. When using the seeker bar, the user directly manipulates the tape head and indirectly manipulates the video content.
The video above describes how DimP works in a bit more detail, showing a few different video scenarios where direct manipulation really shines. It’s intuitive and bizarre at the same time. If the universe is completely deterministic, I can’t help but think this is what time travel must look like.