24p Playback Explained

24p Playback Overview

Though, this metric of a TV is often not noticed by many people, it is important to make note of how well it performs as catching the slightest hiccups can push a good TV towards a great TV.

I measure 24p playback in the three most commons form. Native 24p playback, 24p playback via 60i sources, and 24p playback via 60p sources.

Though they are fundamentally the same, the 3 different sources are often associated with different types of devices. For instance native 24p sources are often associated with movies or Blu-Ray movies while 24p playback via 60i sources are most commonly associated with cable boxes and satellite TV. Finally 60p sources are most associated with streaming devices such as a Amazon Fire Stick, and gaming consoles like an Xbox One or PS4.


 24p-playback-trt
What it is: The smoothing of low frame rate content.
Why it matters: Scenes look more accurate and detailed while smoothed.
When it matters: 24p content. When watching movies or viewing content through streaming devices.

I’ve gone ahead and summarized each source below to help explain a bit more.

The Cause of Judder with 24p Content

It simply comes down to the math of all the content that you’re viewing.
The most common refresh rates you will see on TVs are 60Hz and 120Hz. On the other hand you may see some 240Hz, which is rare.

Then you need to know that the most common types of videos have a refresh rate of 30Hz or 60Hz. Knowing this information it is clear to see that the number divide evenly and very nicely. This lead to smooth information being translated and producing while you watch the TV.

That’s where 24p playback comes into play. 120Hz can divide evenly with 24 content by splitting up five times. This means it can play 24p playback very well and most likely without issue. Whereas 60Hz cannot say the same.

24p-playback-trtIf you look at the above image it is easy to tell what is happening. The purple and light blue colors are not getting as much information as the blue and green colors. This is essentially what leads to judder. Though this can be a small issue unless you are sensitive to judder.

Judder-Free Native 24p Testing

A simple test is done to test native 24p content. I play a 24p video with a 24Hz signal through the TV. The video is simply just a whire square that pass over the TV from left to right and top to bottom. While this is happening I capture the TV screen over 1 second intervals. I’m still a little new to this type of testing, but it seems to work well to best represent judder in TV screen. Below is a failing set of results.

24p-playback-trt

An ideal test result will result in an almost fully grayed-out image. This means the TV is recognizing the signal and correctly distributing the information. Whereas with the above image, the TV failed to properly distribute the incoming signal’s information.

 

Types of 24p Playback

NATIVE 24P PLAYBACK Though a small issue to most, if you’re a DVD or Blu-ray lover you’ll want this metric to pass more than other people. To pass a test the refresh rate must be updated or adjusted to match 24fps. This will reflect in the test image above and the image will be almost entirely gray.  If any of the pieces of the image are not gray or some are while others are not that means the TV failed the test. This means judder is apparent and may by of some worry to many people.
24P PLAYBACK VIA 60I To pass a test the refresh rate must be updated or adjusted to match 24fps. This will reflect in the test image above and the image will be almost entirely gray.  If any of the pieces of the image are not gray or some are while others are not that means the TV failed the test. This means judder is apparent and may by of some worry to many people. The only real difference here is that 24fps information is sent via a 60Hz (60i). So the TV needs to recognize that change that taking place over a 60i signal and adjust accordingly. The only real difference here is that 24fps information is sent via a 60Hz (60i). So the TV needs to recognize that change that taking place over a 60i signal and adjust accordingly.
24P PLAYBACK VIA 60P I find this to be the biggest issue compared to the other two types of playback. This is because it usually involves people that are more immersed than others. The gamers. This metric is more important if you’re interested in video gaming with a smooth picture. It is also important for streaming device like a Roku or Amazon Fire Stick. To pass a test the refresh rate must be updated or adjusted to match 24fps. This will reflect in the test image above and the image will be almost entirely gray.  If any of the pieces of the image are not gray or some are while others are not that means the TV failed the test. This means judder is apparent and may by of some worry to many people. Just like a 60i playback here, all 24fps information is sent via a 60Hz (60p). So the TV needs to recognize that change that taking place over a 60i signal and adjust accordingly.

Motion Interpolation

Often time a a TV can fail a test or will not perform very well. In those case I do not want to give up as that may lead to inconsistent information. So what I do is apply the motion interpolation features (if available) and see if that helps with the testing.
Below are some brands of TV with the most common settings you can turn on to help if you’re experiencing judder.

LG  Menu > Picture > Picture Mode Settings
Turn ‘Real Cinema’ on.
Vizio Menu > Picture > More Picture
Turn ‘Film Mode’ to ‘Auto’
Samsung Menu > Picture > Picture Options
Turn ‘Film Mode’ on
Sony Menu > Picture and Display > Picture Adjustments
Turn ‘MotionFlow’ to ‘TrueCinema’
Turn ‘Cinemotion’  to High

This should help with most issues where the 24p playback is not performing the best.

Conclusion

24p playback causes the scene you’re viewing to looked studdered or more correctly, juddered. There is a little problem that leads to it happening, but often times is not an issue or the TV has tools to help you out. If you are sensitive to any issues like this, you’ll be best off finding a TV that supports 24p playback.
I hope this helps iron out some of the kinks with color gamut.

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