# Why Can't HDMI support real 120Hz?



## badatgames18

HDTV's use interpolation to get the extra fps... while monitors that use dual link dvi can fully utilize the higher fps.

From what i know, isn't hdmi and dvi basically the same thing? If so then why can't hdmi support real 120Hz?

And is there a noticeable difference between monitors that use interpolation and one's that don't?


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## linkin93

Maybe because it can do audio as well? Dunno. What version are you running?


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## Skripka

Quote:


> Originally Posted by *badatgames18;14583805*
> HDTV's use interpolation to get the extra fps... while monitors that use dual link dvi can fully utilize the higher fps.
> 
> From what i know, isn't hdmi and dvi basically the same thing? If so then why can't hdmi support real 120Hz?
> 
> And is there a noticeable difference between monitors that use interpolation and one's that don't?


Dual link has double the TMDS pairs. HDMI is only compatible with single-link ergo is limited to a max of [email protected]


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## placidity

HDMI has nothing to do with refresh rate. The signal is distributed to the tv and the refresh rate of the TV is what smooths out the signal. If the cable is 1.4 category 2 high speed hdmi which you can get on monoprice for like 3 dollars, it is the best it can get.


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## Skripka

Quote:


> Originally Posted by *placidity;14583869*
> HDMI has nothing to do with refresh rate.


O contraire, amigo.

HDMI has a limited amount of bandiwdth. Limited to [email protected]

A fancy cable will not fix that.


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## Riou

Quote:


> Originally Posted by *Skripka;14583888*
> O contraire, amigo.
> 
> HDMI has a limited amount of bandiwdth. Limited to [email protected]
> 
> A fancy cable will not fix that.


That is for older TV's following HDMI 1.2 and earlier. HDMI 1.3 and higher can go above [email protected]


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## badatgames18

Quote:


> Originally Posted by *Riou;14583905*
> That is for older TV's following HDMI 1.2 and earlier. HDMI 1.3 and higher can go above [email protected]


so if i have a 1.4 hdmi cable... i can go higher than 60Hz?


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## Skripka

Quote:


> Originally Posted by *Riou;14583905*
> That is for older TV's following HDMI 1.2 and earlier. HDMI 1.3 and higher can go above [email protected]


Higher revisions can go a bit higher in bandiwdth...but not 120Hz at higher resolutions. 1200p is 7 some odd GBit/sec

But nowhere close to [email protected] HDMI 1.4 is limited to 9 or 10Gbit/sec IIRC. 120Hz 1200p is ~15Gbit/sec I believe, that is 30% short.

EDIT:

I lied a bit. HDMI can do 3D up to 1080:

http://www.hdmi.org/manufacturer/hdmi_1_4/3d.aspx


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## Cyrilmak

I thought HDMI 1.3 and 1.4/1.4a could do true 120hz at 1920x1080 but not any higher?


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## Skripka

Quote:


> Originally Posted by *Cyrilmak;14583994*
> I thought HDMI 1.3 and 1.4/1.4a could do true 120hz at 1920x1080 but not any higher?


See my edit









(For quicker reference: http://www.hdmi.org/manufacturer/hdmi_1_4/3d.aspx )


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## Riou

Quote:


> Originally Posted by *badatgames18;14583943*
> so if i have a 1.4 hdmi cable... i can go higher than 60Hz?


HDMI 1.4a is limited to 1080p / 24 Hz for 3D content. On the other hand, DisplayPort 1.2 can support 2560x1600 @ 120 Hz.


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## Cyrilmak

Quote:


> Originally Posted by *Skripka;14583951*
> Higher revisions can go a bit higher in bandiwdth...but not 120Hz at higher resolutions. 1200p is 7 some odd GBit/sec
> 
> But nowhere close to [email protected] HDMI 1.4 is limited to 9 or 10Gbit/sec IIRC. 120Hz 1200p is ~15Gbit/sec I believe, that is 30% short.
> 
> EDIT:
> 
> I lied a bit. HDMI can do 3D up to 1080:
> 
> http://www.hdmi.org/manufacturer/hdmi_1_4/3d.aspx


Yeah, I was reading, it seems the max bandwidth is the same for hdmi 1.3 and hdmi 1.4. The only difference in the cable is the extra contacts for the audio return and network from what I can tell.


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## Spooony

Quote:


> Originally Posted by *badatgames18;14583805*
> HDTV's use interpolation to get the extra fps... while monitors that use dual link dvi can fully utilize the higher fps.
> 
> From what i know, isn't hdmi and dvi basically the same thing? If so then why can't hdmi support real 120Hz?
> 
> And is there a noticeable difference between monitors that use interpolation and one's that don't?


HDMI is a connection nothing to do with a emulated refresh rate.
Movies and TV use Motion blur, so that if at any time you freeze a movie scene on your DVD player for example, a large part of the scene may consist of blurred objects. Furthermore, the images in a movie or on TV do not have crisp detailed outlines. In a PC game on the other hand, if you take a screenshot or pause the game at any time, you will notice that everything is usually extremely sharp and distinct regardless of how fast it was moving when the shot was taken.

Consider the example of an LCD monitor nominally rated at an 8ms response time. Given 8 milliseconds is 8/1000ths of a second, in one full second it can refresh all the pixels on the screen (if necessary) 1000/8 = 125 times, which makes it equivalent to a 125Hz refresh rate. Yet no 8ms LCD monitor allows you to set a refresh rate even remotely close to this in Windows. One of the reasons is A single DVI digital connection is like an Internet connection, it has limited bandwidth for digital graphics data; not enough to allow higher than 60Hz refresh rate at full 24bpp Color Depth for all resolutions, so typically all resolutions on LCD monitors using DVI are capped at 60Hz. Some LCD monitors using DVI do allow higher refresh rates, and if you're using the newer HDMI digital interface, you can achieve refresh rates of up to 120Hz on appropriate LCD displays. Alternatively, if you use a VGA analog connector you can often select a refresh rate higher than 60Hz on an LCD, though again nowhere near the theoretical refresh rate limit based on your response time

An LCD monitor does not flicker, so for the purposes of reducing eye strain it doesn't really matter what refresh rate is chosen. The default of 60Hz in Windows is perfectly fine in that regard. In fact when using a DVI connection, you may be restricted to a 60Hz refresh rate regardless of resolution, so you may not have any choice. HDMI allows a higher refresh rate on suitable monitors, and using an analog VGA connection gives you the choice of a higher refresh rate at the cost of image quality. However the standard 60Hz refresh rate is still recommended by most manufacturers as the most stable and compatible choice. The only times that the refresh rate on an LCD may actually matter is either for the display of Stereoscopic 3D content

The simple fact of the matter is that LCD monitors have to work on the basis of receiving new frames of information from a graphics card's frame buffer like a CRT would: i.e, during the VBI.


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## Arthedes

so... what cable? displayport, hdmi or dvi?


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