ELI5: Why does the pitch of American movies and TV shows go up slightly when it’s shown on British TV Channels?

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Movies (and some, but not all modern US TV shows tend to be shot at 24 frames a second) British TV runs at 50hz thus to fit nicely in with the refresh rate they play the movie at 25fps. This results in a tiny speed increase, and also audio pitch shifting up ever so slightly.


American TV is 59.94 fields per second, while British TV is 50 fields per second. Movies are shot at 24 frames per second. So in order to broadcast a movie: 1. If it’s for British TV, 24 and 25 are so close to each other that you can just get away with speeding up the movie by ~4%. While this gets unnoticed for video, you can hear the change in audio pitch, especially if a song you know is playing in the film. After the 24fps to 25fps speed change, you just double each frame so it’s 50 fields per second. 2. If it’s for American TV you can’t get away with speeding it by 25%. So a process called 3:2 pulldown is used. First you slow it down by 0.1% so you get 23.976 frames per second and then you split every frame into two fields and every second frame into two fields with one duplicated, so you get a 2-3-2-3-2-3.. pattern and with that 59.94 fields per second with only 0.1% speed change. So why aren’t British TV shows faster when broadcast on domestic TV? Because they are shot at 25 frames per second and then you just have to duplicate each frame to fit into 50 fields per second. While American TV shows are shot at 24 fps.


Me and my girl watch movies over discord, could this explain why she somehow is always drifting ahead of me even though we start at the exact same time? She’s in Australia


When shows are syndicated in the US, I noticed a higher pitch on some channels. This is because they speed up the show slightly to squeeze in more commercials.


beside what has been mentioned here already with FPS differences it may also be another reason that some channels simply show any movie sped up by 10% because that allows you to fit in an entire extra ad break.