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TruMotion - HDTV / Netcast / webOS

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TruMotion - HDTV / webOS / Netcast

Some people ask, "How do I turn TruMotion on or off?"

The short answer is...on most TVs you can't! It is an automatic feature, and I'll explain why.

First, two important attributes:

Refresh Rate (Hz)

This value is the amount of times that the screen will "refresh," meaning if a new frame from the source (cable, dvd, etc) is ready, it will show.

So? What does that mean?

Basically, it's fast! As soon as the new frame is ready, the TV is showing it. Generally, refresh rates are higher than Signal Rates.

Signal Rate (fps)

We know that a movie is a collection of pictures right? They change so fast it appears to show motion.

Signal Rate is the amount of images that change per second. For most (non 4k) programming, this happens at or below 30 frames per second.

So? What does that mean?

30 fps has been somewhat of a standard for a while. Basically, it's fast enough to trick our eyes into believing we're watching real movement, and it works!

But like most things, we want more!


Ok, so what does this have to do with TruMotion?

Let's explain by example.

Say you have a TV with a Refresh Rate of 120Hz (refreshes 120 times per second).

On this TV, we're watching a show on cable with a Signal Rate of 30 fps (offers 30 frames per second).

Every second, the TV will look for 90 frames that it won't find! (because the cable box is only sending 30)

What happens during those 90 frames? Does the TV get confused and blow up?

No! This is what TruMotion does. It fills in the gaps!

At some point, Signal Rates will catch up to Refresh Rates, and TruMotion will get to take a break. But for the foreseeable future, we need it.


Why do some TVs allow you to turn off TruMotion?

Great question! The answer is, there are two kinds of TruMotion. What!?!?

Backlight Scanning

This is the base level of TruMotion, which is necessary to make the Refresh Rate and Signal Rate "Sync." This one cannot be turned off.

In fact, even on TVs with MEMC, that allow you to turn TruMotion off, the setting turns off MEMC but will still use Backlight Scanning. (Because it has to!)

So? What does it do?

This type of TruMotion fills in those missing frames with a copy of the same frame (it's a bit more complicated, but this gets the idea across).


This is the type of TruMotion that can be turned on or off.

This one is a bit more complicated, but here it goes.


Instead of replaying the same frames during those missing frames, the TV instead interpolates to make its own.

Looking at the previous N frames (N being an amount set by the engineers) and sometimes the next frame, the TV makes its best guess.

If 5 previous frames had a red ball rising directly up by 1 inch per frame, we can assume it will rise another inch at the next frame.

If I have 1 missing frame to fill in, and I expect the ball to be 1 inch higher at the Next frame, then I make my in-between frame with ball 1/2 inch higher.

This is the best guess for what the frame would have been, if it part of the original source.


And finally, if my TV does have MEMC TruMotion, how do I turn it on/off?

This is the easy part, it's just a menu setting.

Picture Menu > Picture Mode Settings > Picture Options > TruMotion

*Required question

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