There are many videos on Youtube and it doesn't seem they are being removed, so one might conclude that they do not infringe copyright of the game publisher. But it could also be that for copyright purposes these constitute derivative works, but game publishers are happy to have the publicity and so they don't request Youtube remove the videos.
I have noticed that gameplay videos sometimes miss the game's original sound. One video's description explained that the sound had to be removed since it (naturally) contained music from the game.
Is it possible that video of gameplay constitutes fair-use but audio, at least in some situations, does not?
Are these questions subject to license terms of the video game software?