As the title describes, videos get sped up or slowed down to accommodate for scene framerate:
If the scene framerate is 60fps and a given video is 30fps the video will play at 2x speed (ONLY the video, the audio maintains its speed)
Likewise if a video is 60fps and the scene framerate is 30fps the video will play at 0.5x speed, while the audio remains normal

Weirdly enough this discordance between audio and video remains when applying time stretching, if you try to "undo" the effects of 2x speed by slowing the video down by 50% (setting stretch to 200) then the video goes back to normal as expected but the audio also gets slowed down to by 50%.

(Edit: I'm using version 1.0.0-beta1)