The product specifications specified several times that Pi Max runs in 90Hz asynchronous mode but what does asynchronous display means? I find information about it anywhere? I’m assuming it’s an emulation mode for 90hz on a 60hz but how does it work and how does it prevent smearing issue that one would have with a normal 60hz hmd?
If there’s any info about it in chinese, just post me a link and I’ll use google translate to read it.
@thebunnyrules
As you know, for VR optical system, the left screen with left eye part is entire isolated with the right screen with right eye. VR optical system is much different with normal view system. in the VR system, your left eye can not see the right screen, and right eye can not see the left screen.
So there is a channce that you can update the data to left screen and right screen alternatively. this is what we call asynchronous mode. in the mode, we can achieve equivalent higher FPS. 90 or even more
I am confused by something. Does the head mounted display have an HDMI 2.0 connection, or HDMI 1.4b? Why can’t the HMD simply accept a true 4k 60hz signal?
Also, regarding Asynchronus mode, it sounds like simulated low persistence? Only one eye is receiving an image at a time?
From what I understand, it was tech developed (or stolen, depending on who you believe) by Oculus called TimeWarp. It’s purpose is to increase fps on DK2 and CV1 displays from 75 to 90 by having the display interpolate the odd frame here and there based on the current frame and head movement to give the gpu time to catchup. Think of it as taking a frame and if you turn your head, the hmd will apply a photoshop like rotatation effect to it. It only works well when the known frame and extrapolated frame are close (eg. 75hz actual to 90hz async), Pimax will be going from 60hz actual 90hz, will the async interpolation work as well for such a big jump, not sure. We’ll see when they get the hmd to run at 60hz in 4k. With regards to your comment with regards to the hdmi standar, I don’t know what it didn’t run at 60fps out of the box either.
No, “TimeWrap” is total different with our frame boost algorithm.
The whole image process system in headset fully support 4K 60Hz signal imput, and the customized 4K display always works in 4K mode. the only limitation is the bandwidth of HDMI 1.4b. So we need compress the 4K 60Hz signal into 4K 30Hz bandwidth, then do decompress in headset, we’re working on that.
As you know, for VR optical system, the left screen with left eye
part is entire isolated with the right screen with right eye. VR
optical system is much different with normal view system. in the VR
system, your left eye can not see the right screen, and right eye can
not see the left screen.
So there is a channce that you can update the data to left screen and
right screen alternatively. this is what we call asynchronous mode. in
the mode, we can achieve equivalent higher FPS. 90 or even more
Oh, I see and now I understand your previous explanation more. You’re not using a projection algorithm of timewarp but using two screens and having them refresh asynchronously to creat the feel of 90hz.
May ask, why did you choose hdmi 1.4b? I understand the reasoning of wanting your HMD to be compatible with previous gen GPUs that don’t support 2.0b but if you would have gone with Displayport 1.2 which has been on GPUs since 2010, you would have had 17.5Gbit of bandwidth to work with instead of 12gbit on the hdmi 1.4b?
Updating the screen alternatively for each eye is actually a pretty damn brilliant way to overcome LCD limitations. Low persistence on rift and vive is essentially having relevant frames showing for only a fraction of time, with the screen blank for the remainder. So, if both eyes have miliseconds where no image is displayed, it would simulate low persistence. It seems like it will get better as the motion to phonton latency goes down.
PimaxVR why are you not using 4:2:0 chroma subsampling to enable 4k 60hz?
The 4K 60Hz strategy appears to be detailed over on the Chinese site, under the “Schematic of the 4K60Hz signal processing” section at the following translated location: https://translate.googleusercontent.com/translate_c?depth=1&hl=en&prev=search&rurl=translate.google.com.au&sl=zh-CN&u=http://bbs.pimaxvr.com/read.php%3Ftid%3D43%26fid%3D8&usg=ALkJrhicRGD2yRHI18V6Bijj7ziiMsbUow
Would be nice if they would just put that in English on the main web page in the interest of full disclosure for customers. It makes the product seem way less shady.
I got the file In. English. It was email to me by one of the guys at Pimax you can download it here https://drive.google.com/file/d/0B_ZK0KoOmrrCS0IwTlBOWGdsNG4ydHFQaHBteVNYY0RuSGpV/view?usp=drivesdk
@thebunnyrules，
One of the inmportant reasons that we choose HDMI not DP is mainly related to the VR contents. Since DK2/CV1/Vive they all use HDMI port. At early stage, it’s better we choose same video port. otherwise, there should be more workload or compatible issues. we don’t wanna build a high feature VR headset but with very limit VR contents.
In addition, we think we might have the chance to implement 4K 60Hz on HDMI1.4B by SW compress/decompress algrithom.
Thanks for your understanding!
@VRGIMP27,
Thanks for your good suggestion about using 4:2:0 chroma subsampling to enable 4K 60Hz, we will let our engineer team evaluate this and keep you update. 
How can this mode be used with Pimax 4K?
Is there an option on the piplay software?
no one knows, probably it cant be used:)