As a thought experiment, I'm imagining an observer on Earth video conferencing with an observer traveling at a high velocity away from Earth, or in a very large gravitational field relative to Earth.
What would a live video feed look like to each observer? Would the video of the observer on Earth appear in slow motion proportional to the intensity of the gravitational field where the other camera is located?
Would the observation of either observer change if the signal carrying information to build the video was traveling at the speed of light? I don't intuitively understand how the time dilation could be observed if the information was being received by either observer at the speed of light.