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!! Why my tv doesn't get 120/240 hz !!

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Old 06-06-2012, 08:51 PM   #1  
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Default !! Why my tv doesn't get 120/240 hz !!

What confuses people is the manufacturers tout the 120 hz and 240 hz LCD HDTVs and don't really explain very well what that means. The 120hz is the rate that the screen is updated, not the signal being received by the TV. It is done for various reasons to improve the picture quality.

Most 120 hz LCD HDTVs will accept a 1080p at 24 frames per second, a 1080p at 60 frames per second and a 1080i at 30 frames per second input signal. In the case of the 24 frames per second the frames are duplicated 5 times (24 x 5 = 120) and the 60 frames per second are duplicated 2 times (60 x 2 = 120). Lastly the 1080i signal is deinterlaced making 30 frames per second then each frame is duplicated 4 times (30 x 4 = 120).

Even when you go to the movies you are actually watching a 48 frame per second screen update even though the movie was shot at 24 frames per second. Each frame is displayed twice to reduce flicker without having to use twice the length of film.

The 30 frames per second (25 frames per second in Europe) broadcast standard was adopted many years ago at the birth of TV. It has exclusively been used up until the ATSC digital broadcast standard was adopted. At that time the progressive formats were added, but only within the bandwidth the channel spacing would allow. Thus only 1080p/24 and 720p/60. The 1080p/60 is not a broadcast format at all and right now only available via computers, some satellite/cable receivers, some Blu-ray and media players. And now cell phones.

So the bottom line is to recognize the difference between the refresh rate of a display from the format of the signal being fed to the display.
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Old 06-07-2012, 09:01 AM   #2  
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Great explanation of something often presented in a vague way by dealers and manufactures.

Another issue with these 120 and 240 Hz receivers is that some offer "frame interpolation" and actually generate more differing frames than the source provides (artificially upping the refresh rate). An example is a picture sent at 30 frames per second. The set uses these frames to "guess" at frames in-between and come up with 60 (or 120) frames per second that show up on the screen. Some people like the picture this provides, but in general, most don't since it gives the picture a "soap opera" appearance, particularly if the original frame rate was derived from film (24fps). Most sets allow frame interpolation to be turned off and then you're back to showing several identical frames that match the source rate, which in my experience is preferable for most viewing.
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Old 06-07-2012, 01:27 PM   #3  
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Old 06-08-2012, 12:43 PM   #4  
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Quote:
Originally Posted by leevitalone View Post
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What does this mean? Is it a local saying somewhere? I googled it and they don't know what the heck you are saying.
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Old 08-18-2012, 10:12 AM   #5  
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Old 10-25-2012, 05:24 PM   #6  
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This is a good point, but I don't want anyone to be mistaken about the implications of this. Even though a blu-ray may only provide 24 images per second, you wouldn't want to buy a TV with a 24 Hz refresh rate. It would look terrible and would be hard to watch comfortably. Your post gives manufacturers a hard time about advertising 120 Hz / 240 Hz without explaining what it means, but I don't think that's the case at all. The "Hz" rating designates how many times per second a screen is refreshed (just like on a computer monitor), and that is what they provide. Granted, some manufacturers have started coming up with their own, deceitful methods, but lets set those aside for the moment.

For anyone reading this forum while trying to buy a TV, don't interpret this to mean that you're good buying an LED TV with a 60 Hz refresh rate - you will regret this decision. If you look carefully, you can easily tell a 60 Hz display from a 120 Hz display when they are standing next to one another. I would recommend buying a 600 Hz sub-field plasma or a 120/240 Hz LED display if you're looking for strong performance while watching motion like sports.

There's a lot more to this in the underlying hardware. For an explanation of why this happens, take a look at my other post on refresh rates:
http://www.highdefforum.com/1284390-post3.html

Last edited by ThePauper; 10-29-2012 at 04:57 PM.. Reason: Adding Information
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Old 11-24-2012, 09:22 PM   #7  
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I find it interesting the Xbox 360 only puts out 60 hz. If that's all someone is planning on doing, it would be pretty pointless to buy a TV with a higher refresh rate
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Old 11-25-2012, 09:31 AM   #8  
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Quote:
Originally Posted by ThePauper View Post
This is a good point, but I don't want anyone to be mistaken about the implications of this. Even though a blu-ray may only provide 24 images per second, you wouldn't want to buy a TV with a 24 Hz refresh rate. It would look terrible and would be hard to watch comfortably. Your post gives manufacturers a hard time about advertising 120 Hz / 240 Hz without explaining what it means, but I don't think that's the case at all. The "Hz" rating designates how many times per second a screen is refreshed (just like on a computer monitor), and that is what they provide. Granted, some manufacturers have started coming up with their own, deceitful methods, but lets set those aside for the moment.

For anyone reading this forum while trying to buy a TV, don't interpret this to mean that you're good buying an LED TV with a 60 Hz refresh rate - you will regret this decision. If you look carefully, you can easily tell a 60 Hz display from a 120 Hz display when they are standing next to one another. I would recommend buying a 600 Hz sub-field plasma or a 120/240 Hz LED display if you're looking for strong performance while watching motion like sports.

There's a lot more to this in the underlying hardware. For an explanation of why this happens, take a look at my other post on refresh rates:
http://www.highdefforum.com/1284390-post3.html
The implicatiopns are that on a computer monitor you have the capability of feeding a signal faster / greater than 60 hz while with broadcast tv (2d) you will never feed a signal faster than 60hz. With 3d you need 120 hz since the eyes alternate this gives each eye 60 fps. The subfield drive in a plasma is different than refrsh rate - they still only refresh at 60 hz but the pixels are 're-lit' for lack of a better term 10x per each refresh (10x60=600).
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