120hz over HDMI

[RutgerB]

Hi! Today I bought the Samsung S23A750D 3D 23'' monitor. Biggest reason for this was the 120hz.

The monitor only has a HDMI and DisplayPort connection. I thought my Ati Radeon 6870 had DisplayPort, but this appeared to be a DisplayPort mini. Since I had no DisplayPort to DisplayPort mini or DVI convertor I hooked it up with a HDMI cable.

Problem: I can't select 120hz in windows settings or in the Ati drivers.

I also tried hooking it up to my Laptop, which has an Nvidia GPU. The Nvidia drivers have a force custom resolution option, so I forced 1080p@120hz, but this only gave a black screen. (also used an HDMI cable)

So my question is essentially; Is it possible to get 1080p@120hz over HDMI? and if so, how do I do it? Or do I need to get a DisplayPort to DisplayPort mini convertor?

 

[Chainzsaw]

The refresh rate of your 120Mhz LCD is just that, a refresh rate. I would not try and force any resolutions or speeds.

Basically what happens is that your computer usually refreshes at 60Hz. But with a 120Hz panel it "upconverts" it to 120Hz automagically. So even though you are sitting at 60Hz - your LCD is doing twice the amount of work - all without you even seeing a thing (well maybe you can).

http://forums.cnet.com/7723-13973_102-312626.html

http://www.avsforum.com/avs-vb/showthread.php?t=736064

Hope this helps.

 

[Chainzsaw]

One more thing:

http://www.overclock.net/monitors-displays/662628-60hz-vs-120hz-explained.html

"Don't forget though, to truly see the benefits of a TRUE 120hz monitor, you must be gaming at an average FPS greater than 60(ideally over 120fps). When your average frame rate is above 60(for this example let’s say you are averaging 120fps), you WILL see the in between frames that a 60hz monitor could not display. For a list of TRUE 120hz monitors, see nvidia's page on monitors that are compatible with their 3d technology.]"

That pretty much sums it all up. 120hz works well if you get over 60FPS.

 

[Kari]

hdmi doesn't have enough bandwidth to transmit 1080@120Hz, just get a mini-dp to dp cable and problem solved

 

[RutgerB]

I just read the samsung manual and indeed it seems that I need to use the DP cable.
What I find annoying is that with displayport there are again multiple cables, the normal one and the mini one.
I thought that displayport was always "mini".

 

[Chainzsaw]

Alright my bad. I totally forgot HDMI doesn't have enough bandwidth (for 120Hz). Good job Kari for catching that!

 

[Kari]

though what I don't understand is why Samsung didn't include dual-link dvi on that monitor... the cost savings can't be that high on so common parts...

my poor 5770 doesn't have any dp outputs

 

[Chainzsaw]

I kind of hate all these HDMI/DP/DVI standards. They should just move to 1 and be done with it, like we had with VGA back in the "good 'ol days".

 

[RutgerB]

Agreed. I was hoping DisplayPort would replace all DVI and hdmi standards, unfortunatly now we already got normal dp and dp-mini. Why not make them all mini?

Right now I'm seriously considering returning my S23A750D and getting an S27A750D or even pay some extra bucks for the slicker design of the S27A950D

 

[gnomio]

Do hdmi have enough bandwidth for 1080p at 120hz?

 

[RutgerB]

Do hdmi have enough bandwidth for 1080p at 120hz?

As kari and I found out: Nope

 

[wolfram23]

You just need something like this

http://www.newegg.ca/Product/Product.aspx?Item=N82E16812270263

 

[jonjon32]

As kari and I found out: Nope

It appears that HDMI goes way further than Samsung thinks (or wants as to think). I forced the s23a750d as high as 1080p - 100Hz on HDMI with a GTX580 and looked really good.
When I tried 120Hz (1080p) the screen deteriorated, started flickering and produced artifacts. A message popped up saying "mode not optimal". I reverted to 60Hz and everything was OK (no obvious damage or any change on the display)
It appears that HDMI has enough bandwidth to reach ~120Hz. I am currently waiting for a 1.4a HDMI cable to test if the flickering was caused by the cheap HDMI cable I use (restrictions on bandwith).
Samsung's manual says that the optimal/ maximum resolution for HDMI is 1080p 60Hz but the HDMI socket used is 1.4a version.
This little experiment proves that maybe there is something there. After all, how can all those 3d TV sets handle 1080p at 60Hz X 2 (for 3D) on HDMI?
Not all refresh rates are supported (i.e 90Hz gives you a black screen and a message "mode not supported").
I let you know when i get the 1.4a cable.

 

[SantyXtra]

@jonjon32
Did you manage to transfer 120Hz on HDMI?
Please share your feedback, I have exactly the same concern:
HD7850 to Projector via 30ft cheap HDMI cable @ 720p, 120Hz resulting in flickering with color bands and grains.

 

[bystander]

HDMI does not support 120hz at all at version 1.4a and below. You'll have to wait until 1.4b. It is not entirely a bandwidth issue, it is also a frequency issue. The closest thing available is 3D @ 60hz using a maximum of 720p. Due to allowing you to send both the right and left eye image in a single transmission, it can manage to display both the left and right images at 60hz (or a combined of 120hz). This is only due to frame packing two images together. This doesn't work except for 3D, as both left and right images are generated together, so they can be sent together.

 

[SantyXtra]

Thanks for the reply. This gives raise to two more questions

1. Then why do monitors/ projectors accept input signals of 120Hz when there is no cable to transmit that frequency?
2. Is there any way I can enjoy 3D on my 720p 3D ready projector without a convertor? I thought since Projector is compatible with 120 Hz and graphic card can output 120hz, all I need is a player and DLP glasses to get 3D?

 

[bystander]

Thanks for the reply. This gives raise to two more questions

1. Then why do monitors/ projectors accept input signals of 120Hz when there is no cable to transmit that frequency?
2. Is there any way I can enjoy 3D on my 720p 3D ready projector without a convertor? I thought since Projector is compatible with 120 Hz and graphic card can output 120hz, all I need is a player and DLP glasses to get 3D?

1) Monitors do, through dual link DVI or displayport, projects don't, unless you can find them with those connectors, which I do not believe they do. They do, however, take 24hz - 60hz of input and create additional frames from them.
2) Like I mentioned before, through frame packing, they can create 3D at 60hz per eye at 720p, which is 120hz worth of displayed data. They do this by sending both the right and left eye's images as a single transmission to the monitor with frame packing. The monitor then splits up that transmission into left and right images, and displays them sequentially, and your glasses allow the correct eye to see the correct image.

Simply put, HDMI 1.4a and below can only deliver up to a max of 60hz of images, but since a single image in 3D is made up of 2 images, frame packing can deliver the two images at once, but bandwidth limitations limit you to 720p.

 

[SantyXtra]

Thanks.. really appreciated.

Any other way of answering my question?
Can I get sequential and SBS 3D on my setup without a converter in between?

I have read that display port cable can handle 120Hz

But my projector has no DP input:
Connections

If I get a DP to HDMI adapter/ convertor, will that not add bottleneck resulting in same limitation?

 

[bystander]

Whether or not it can do sequential and SBS 3D is up to the projector. HDMI will not limit you beyond the 720p limitation mentioned. You'll have to read what the converter it capable of supporting and go from there.

A DP to HDMI adapter is still limited by its weakest link.

EDIT: For the projector to work, you will need it to support HDMI 1.4a. Anything less will not work. That is the requirement for AMD's support for HD3D.

 

[SantyXtra]

Just posting my experiment results here for others' knowledge
120 Hz works seamlessly on HDMI

Which means you just need a pair of 3D DLP glasses to enjoy 3D on your 3D ready DLP projector provided you have a supported graphic card

This is Optoma HD66 connected to HD7850 through a 10ft Beklin HDMI cable

 

[bystander]

While that is 120hz, it only accept 60 FPS of input. In 3D that allows for 60hz per eye, but in 2D, it only accepts 60 FPS and operates at 60hz, unless you use the mode that allows it to double the inputted frames, which is not good for computing, only for TV and movies.