![]() ![]() We don't have a way of knowing which technique the TV is using since we would need a high-speed camera and have to check to see how many times it's refreshing. Since the incoming video has a 3:2 pulldown and the TV can't change that, it either switches to a 48Hz or 72Hz refresh rate, then it either multiplies or triples every frame to remove the judder. Firstly, the TV needs to recognize that it's playing a 24p film, then it adjusts itself to remove judder. Removing 24p judder from a 60Hz TV like a streaming box or cable box is more complicated. It's easy for 120Hz TVs to remove 24p judder because they display each frame five times. TVs can't drop down to 24Hz, which explains why it still has to increase the frame rate to match either 48Hz or 72Hz. A 60Hz TV will either drop its refresh rate down to 48Hz or slightly increase it to 72Hz so it can multiply the frames by an even number. It's a fairly straightforward process for a TV to remove judder from 24p sources or native apps because it receives a 24p signal directly. The judder itself looks the same from a native 24p source or a 60p source, but the difference is that it's harder to remove from a 60p source, and we'll explain later in this article how TVs do that.Īdditional Information How a tv removes judder From a 24p source or native app However, if a 24p video is coming from a 60Hz source, like a cable box, it's harder to remove the 24p judder because it has to try to manipulate a 60p or 60i signal. Most TVs can remove 24p judder from native apps or native 24p sources because they receive the 24p signal and can manipulate the frames how they want. The cause of judder on 24p via 60p/60i video Frames #1 and #3 repeat twice, while frames #2 and #4 repeat three times, so they stay on the screen 50% longer. To remove judder, the TV wants to display each frame for an even amount of time.Ībove is a diagram depicting the cause of judder. However, this means that every second frame is held on longer than the next frame as it stays on the screen for 50 milliseconds compared to 33 ms this causes the juddery motion. So what TVs do is called the 3:2 pulldown (also called telecine): the odd-numbered frames repeat twice, and the even-numbered frames repeat three times to get 60 frames. Even if the TV doubles each frame, there are only 48 frames per second, and it's still missing 12 to reach the 60 fps needed to match the 60Hz refresh rate. However, judder is most noticeable on 60Hz TVs because 60 isn't a multiple of 24. Likewise, most 120Hz panels can display 24p video without issue because 24 goes into 120 five times. For example, a 120Hz TV would just multiple each frame four times from a 30 fps video. TVs commonly have one of two refresh rates: 60Hz and 120Hz. 30 and 60 fps videos divide into those refresh rates evenly, making it easy for the TV panel to get the video to meet the panel refresh rate this is what motion interpolation is for. If you do notice it and it bothers you, make a point of getting a TV that can, but most modern TVs can remove judder from at least 24p sources anyways. If you don’t notice the judder on the left, or it doesn’t bother you, there’s no need to worry about getting a TV that can do judder-free 24p. The slow-motion videos are exactly what they sound like: slowed down to show the effect of judder, but you won't see films like that anyways. If you’re wondering whether it’s an issue for you, take a look at this video and compare the look of the 24p with judder (left) to the judder-free 24p video (right). Overall, 24p judder isn't a major problem most people won't even notice it. 24p judder only matters when you watch movies because it's the only content shot in 24 frames per second if you don’t watch movies, you have nothing to worry about. ![]()
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