Display Refresh

[dek]

Are there any ways to override the 60hz display refresh rate (monitor) on the guest os? I got a 120hz monitor, cant raise it in windows 7 guest os above the 60hz. Running from Ubuntu 10.04. Ubuntu runs 120hz fine.

[frank]

It does not make sense to change that frequency from within the guest. The guest can see only virtual devices, therefore you have to change such settings on the host.

[dek]

thats bs frank. the guest os is running a virtual adapter for my refresh rate and screen resolution. changing it takes place in the guest os.

i dont know why the display adapter drivers in virtualbox are limited to 60hz. i guess they think all monitors are lcd 60hz. but on a 120hz monitor 60hz becomes real choppy, and when its slow and choppy its a pain in the a** to work with. changing display refresh should have no impact on performance either. hoping some of you have some workarounds or maybe i should mail them better.

[frank]

I don't know what you mean by choppy. The guest actually has no idea about the frame rate of your host display. The guest display adapter is virtual, that means that everything which is drawn by the guest is forwarded for the host graphics adapter. Therefore it is not possible to change the refresh rate of the guest and it is also not necessary!

The display refresh rate is actually a setting which defines how often the content of the physical graphics memory is written to the monitor. This setting was important for older CRT displays: The more often the picture on the screen was refreshed, the better the experience. 70Hz or better (some users still see some flickering with 80Hz but this also depends on the monitor) was a good value for such old monitors.

With LCD monitors, there is no flickering anymore but the refresh rate can still be important when displaying fast changing content (videos, computer games). 60Hz are usually enough (remember, the usual movie refresh rate is 30 fps) but for some 3D computer games where the monitor has to display alternate pictures for the left eye and for the right eye, 120Hz is necessary (60Hz for each of the eyes).

But even in that case, this setting is a HOST setting not a GUEST setting! So properly configure the refresh rate of your graphics card at the host and the guest will use the same refresh rate.

[dek]

I belive my my host is setup correctly, my display boots into 120hz and the drivers automaticly configured the monitor with the monitors native settings. "120hz LCD"

How do I make sure Virtualbox are getting the right settings? any place i can change some paramters to force things to work my way? or some things i need to make sure is setup on the Host?

[MarkCranness]

You have to trust that your guest IS getting 120Hz even when its virtual hardware says 60Hz.
Re-read what Frank said about the guest display adapter being VIRTUAL: It is all done with software and there is no real guest display. NOTHING on the guest refreshes a monitor at 60Hz or 120Hz or any other Hz. The guest refresh rate settings are fake and ignored.
The VirtualBox programs running on the host take data from the virtual VM display buffer and copies it to your real host display buffer and your real video card sends it to your real display at 120Hz.

[dek]

NONSENSE. i installed xp as a guest os and had the option between 60 and 85hz and it was cleary a difference in how the screen updated. you people must understand that the refresh setting on the guest OS is as real as changing the screen resolution on the guest. dont tell me that the guest is still running your host resolution when cleary the adapter changes on the guest is physicalle doing changes to how the guest os is being rendered on screen. Try changing the screen resolution on your guest os and tell me if it doesnt do anything. And please dont tell me that windows has nothing to do with changing its refresh rate in the monitor on the os. Its a feature of the OS and has nothing to do with Virtualbox.

[dek]

yea, my guest is getting 120hz. allright, i can trust u lol, but windows does NOT output 120hz, in that you have to trust me.

[Sasquatch]

Why are you so obsessed with 120 Hz? Humans can't see more than 24 frames per second anyway, and 60 Hz is 60 frames per second (1 Hz = one refresh per second). There is no benefit to 120 Hz vs 60 Hz that the Guest should output. Your guest gets it's 120 Hz refresh no matter how you look at it. Windows is lying all the time. If you don't believe me, just copy a file from one location to another, it's flat out lying how long it takes.

[frank]

yea, my guest is getting 120hz. allright, i can trust u lol, but windows does NOT output 120hz, in that you have to trust me.

I still don't understand how you measure that. Well, it could be that the graphics output of the guest is not that fast updated like when you run an application on the host, that is, scrolling in the browser might be a bit slower because there is the virtualization overhead. But just having a static image (no content change), how do you measure the screen refresh rate?

[dek]

i cant measure it but, i know the difference, sure, there are some chops and lags since its virtualization, but it doesnt matter how graphic intensive or much of a load it take on the system, all windows acts the same, its constant and its just like if i switch to 60hz on this monitor, since the monitor properties in windows says 60hz and there is no other option i guess the virtual box graphics adapter is locked on 60hz as well. i doubt i would get any help on this since you guys are asking questions and putting up subject around the issue. i could be wrong but i have done several different virtualizations on different Os's. parrallels, vmware both mac and pc and ive never seen "choppiness" like this coming from the virtualization, i got a fairly decent system too, ssd and 3ghz dual core, with 4gb's ram and 8800gt with 5125mb ram, running on a minimalist lightweight xfce ubuntu setup...

[mmd]

Who said humans only see 24fps? That's not true at all..

Watch a movie. That is 24fps.. Now go watch something like football on a nice HDTV.. Notice how football is more fluid in motion? That is 60fps.

(I know this because I'm a video editor, so I know a thing or too.. The limit is really at 60ish, but NOT 24.. You can even see the difference between 24 and 30.. Some B movies are shot at 30fps, and you can sometimes sense it)..

[Sasquatch]

Who said humans only see 24fps? That's not true at all..

Watch a movie. That is 24fps.. Now go watch something like football on a nice HDTV.. Notice how football is more fluid in motion? That is 60fps.

(I know this because I'm a video editor, so I know a thing or too.. The limit is really at 60ish, but NOT 24.. You can even see the difference between 24 and 30.. Some B movies are shot at 30fps, and you can sometimes sense it)..

Then read this: http://www.100fps.com/how_many_frames_c ... ns_see.htm, it's good stuff. Perfect explanation of what is going on in the world of 'fluid', 'blurry' and 'jerky' pictures/video. There are other sites and information sources to give the same idea, some with more detailed information, some with less. But this isn't the topic about human eyes and frames per second, it's about a screen's refresh rate.

dek, who do you believe when your speedometer in your car says you're going at 100 KM/h but the police who use a laser based speed calculator tell you you did 95 instead? The VM is like the speedometer, but the other way around. It will say it updates 60 times a second, but the physical monitor still shows you the display at 120 Hz. You can't have a part on your monitor that tunes down to 60 Hz.

[mmd]

Who said humans only see 24fps? That's not true at all..

Watch a movie. That is 24fps.. Now go watch something like football on a nice HDTV.. Notice how football is more fluid in motion? That is 60fps.

(I know this because I'm a video editor, so I know a thing or too.. The limit is really at 60ish, but NOT 24.. You can even see the difference between 24 and 30.. Some B movies are shot at 30fps, and you can sometimes sense it)..

Then read this: http://www.100fps.com/how_many_frames_c ... ns_see.htm, it's good stuff. Perfect explanation of what is going on in the world of 'fluid', 'blurry' and 'jerky' pictures/video. There are other sites and information sources to give the same idea, some with more detailed information, some with less. But this isn't the topic about human eyes and frames per second, it's about a screen's refresh rate.

That site is already quite questionable.. Motion blur comes from shutter speed, which is independent of fps.. I can easily film a movie with low shutter and fast shutter, both at 24fps, both will still have the same motion (as long as my shutter doesn't go under 1/24th-sec).. If I shoot say, at a shutter of 1/100, at both 24, 30, and 60fps, you will see a massive difference on the 60.. The 24 and 30, not so much... Sorry, but that site is as bad as making a floor, and saying "go jump on it to test it"..

As for this post, the virtual machines refresh rate and host is totally based on the host.. Maybe any difference seen is the guest OS, any setting chose, tells windows how many times to vsync.. That's probably the only difference, but i've even see real PC video cards fail, and when you set 60Hz, it really did 70Hz, so the setting is purely likely in the video card, and since the video card in this case is virtual, I don't honestly think there's gonna be a difference...

[dek]

i know my monitor is on 120hz,that doesnt change, im talking about the display adapter being locked at 60hz. alas windows outputs 60hz not syncing up to my monitor, alas choppiness.