Advice on connection please

JasonKnights · 29 Apr 2011 at 22:42

Hi there, I run my pc through a samsung 50inch 3D plasma which is 600hz. I use a hdmi lead from my gtx295 (being replaced with gtx580 tomorrow) to my Sony 5.1 surround sound system which has 3D pass through. And the another hdmi goes to my display from the receiver. When I use the pc the highest hz I can achieve is 60hz yet I've seen others with 120hz? If I run the hdmi lead from my gpu straight to the tv will this make any difference? I've read into hz and know why TVs are eg 100hz to accept multiple signals from multiple devices from around different regions. Just want to know how to acheive 120hz or above! Thanks

Surveyor · 29 Apr 2011 at 22:57

It's not really 600Hz in the way that a PC sees it.

In a Plasma TV there are 8 or 10 sub fields. Each sub field refreshes at 60 frames per second which basically gives the number. 10 sub fields X 60 fps = 600Hz.

The highest you refresh rate you can use is 60Hz. 600Hz is then just magic done by the TV and is mainly a marketing tool.

cmndr_andi · 29 Apr 2011 at 22:58

Hi there, may I ask what your specific Tv model number is? Also, when you say others are running at 120Hz, do those have the same TV as you, a different TV or a PC monitor?

As for 600Hz, this is just frame interpolation (the TV makes up frames between the 60Hz input signal to make the moving image look smoother) this isn't the same thing as the monitor accepting a 600Hz input signal and accurately displaying each frame that is sent. Have a look at this article.

Since you are connecting through a GTX 295 (which is not HDMI 1.4 enabled) then the HDMI connection can only send a 1080p @60Hz signal or below to the TV. But the TV will then do its 600Hz interpolation cleverness to make it appear smoother - but often this doesn't really work as well as expected since it is basically guessing.

However, with your new GTX 580 card - this is HDMI v1.4 enabled - so you will be able to run 3D content on your TV (though it can only be 1080p@24Hz or 720p@60Hz due to bandwidth constrictions). As for running the TV at higher than 60Hz in 2D over a HDMI 1.4 connection - I just don't know. However in PC monitors at least you need a much higher bandwidth connection (dual link DVI) to send a 120Hz signal to a 1080p 120Hz monitor - and since the HDMI 1.4 spec isn't any higher bandwidth than the 1.3 then I don't suspect you will be able to push the TV to run a 1080p video signal above 60Hz.

JasonKnights · 29 Apr 2011 at 23:08

The tv is Ps50c680 which I use as a monitor. And the 120hz I've seen was on a different monitor. I have tried 3D gaming and it works fine even though the output is 1.3 (I use a 1.4 lead). The display performs great but with me upgrading the gpu I wondered if I wired it all up different I might achieve higher hz. Thanks

cmndr_andi · 29 Apr 2011 at 23:24

Yea, that's the thing - the TV implementation of 3D is quite a bit different than the monitor implementation.

On monitors they are basically dumb outputs that accept a 120Hz video signal through the dual-link DVI connection and the graphics card and the PC do all the clever stuff (producing the images for each eye and syncronising them).

In contrast, with TVs they accept a HDMI 1.4 compliant signal (eg. 2D @1080p @ 60Hz, 3D @ 1080p @ 24Hz or 3D @ 720p@ 60Hz) and do all the clever stuff to output an image that looks great and is 3D if it should be (with use of the glasses that the TV synchronises). Since it is set up this way you get some nice 3D effects, everything looks good and it is simple to set-up. However, it doesn't give you the same flexability as a 120Hz monitor with a dumb dual-link DVI input - so it is very unlikely you will be able to run the TV in 2D mode at anything higher than 60Hz (not to mention the HDMI 1.4 spec doesn't seem to support it).

As for the GTX 295 and 3D I stand corrected - it may not be a 1.4 card but it is able to output a 1.4 signal with current drivers.

JasonKnights · 29 Apr 2011 at 23:35

thanks for your help. I am very happy with the visuals etc I very rarely use 3D but for the price I paid it wasnt worth not getting the 3D and its always there for if I do. mu main concern was if I was slowing down performance by running the video signal through the surround sound instead of directly to the TV but seems like Ive got it all set up correct :-)

thanks again for your time