Projector fans rejoice! BenQ HT2550 can do 1080p 120hz

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Projector fans rejoice! BenQ HT2550 can do 1080p 120hz

Post by BattleAxeVR » 17 Dec 2017, 17:00

Hi guys / gals, I thought I'd share some good news I came across while digging through the Chinese manual for the new 4K (pseudo 4K or Faux-K) projector by BenQ, model HT2550 (US) or W1700 (Europe / Asia):

Scroll down to page 43. It also supports 2560 x 1600, which could be interesting to some gamers, although it's an odd aspect ratio that doesn't match the DMD's native 16:9. Although even if I ran my game at lower res I'd still rather my GPU do the upscaling to 4K.

Supports 3D too. I wonder if NV 1080p 60hz per eye frame sequential 3D will work too.

1080p 120hz uses a 300 Mhz pixel clock, and these projectors can handle 600 Mhz for 4K60, so it might be possible for them to support 1080p 240hz natively eventually via firmware update.

And if you can leave the XPR pixel shifter on whilst doing 1080p 240hz, then a bit of processing or integration into a game engine could yield something akin to 4K 240hz! Just jitter your sample coords.

Now isn't that exciting! May 2018 bring us all nice things. I bet other manufacturer's implementation of this chip will do 1080p120 as well.

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Re: Projector fans rejoice! BenQ HT2550 can do 1080p 120hz

Post by open » 17 Dec 2017, 23:22

I would love to have one. Especially if it has low or virtually no pixel response time. I think the best option would be something like downsampling from 4k. It's not as clear but still nice.

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Re: Projector fans rejoice! BenQ HT2550 can do 1080p 120hz

Post by BattleAxeVR » 18 Dec 2017, 14:46

Like I wrote in the other thread, it's likely possible to pack four independent 1080p frames into a single 2160p frame, with different timestamps, such that when the projector shows each pixel in a 4x4 block in sequential order, displaying the sub images at the appropriate spatial and temporal offsets results in something akin to 4K 240hz. It's just re-correlating the sub-frames to the right timestamp.

No downsampling at all, it would need point sampling, so stay razor sharp. This scheme is rather analogous to interlaced displays of yesteryear, so e.g. 1080i would be 1920 x 540 even lines shown at time t0, then 1920 x 540 odd lines shown at time t1, non-overlapping in either time or spatial dimensions. Interlaced cuts the lumens in half (1/2 the lines are black each sub-field), but this type of shifting projector has overlapping pixels spatially, so no loss of aperture ratio (90% or more for a DLP) or lumens but at the cost of some sharpness. However because the overlapping pixels are shown at different times, your visual system does get insights into the real video signal.

See the other thread with appropriate shadertoy. Mark also wrote a neat TestUFO as a proof of concept for both 2X and 4X shifting DLP wobulating projectors. (which have lower native resolution but still display 8M distinct pixels on screen).

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Re: Projector fans rejoice! BenQ HT2550 can do 1080p 120hz

Post by Chief Blur Buster » 18 Dec 2017, 23:47

Wobulation is a creative kind of interlacing at the single-pixel level. Left-right, up-down, diagonal, rotational, etc.

This has been around for a while, e.g. ten years ago, 960x1080 DLP chips displaying 1920x1080 via left-right vibrating at 120Hz (displaying two subfields per refresh cycle).

In the past, video game consoles and early 8-bit computers, took advantage of NTSC 30Hz signal of using the two subfields for 60Hz temporal resolution, ala creating 240p out of 480i. Or even keeping 480i but having the temporal resolution of 60 images per second in a 30Hz signal.

The "increase-Hz-during-wobulation" tricks kind of takes advantage of that.

Yes, I created a brand new TestUFO based on having seen that ShaderToy and collaborating. It amplifies refresh rate by frame-packing extra frames in the temporal wobulation -- achieving up to 240Hz on some 60Hz projectors (4X pixel shifting cycles) and 120Hz on some 60Hz projectors (2X pixel shifting cycles) even some nearly-10-year-old DLP HDTVs, provided 1:1 pixel mapping is achievable via PC input.

The TestUFO pattern "extra refresh rate via wobulation" motion test is now in internal beta testing. It will be announced shortly (and spread to the home theater forum channels too). I used to be the forum moderator of one of the topic areas (HTPCs) on one of the world's biggest Home Theater forums, at AVSFORUM (over 7,000 post in my name) so it'll be an interesting crossover TestUFO that applies to high-Hz gaming and the use of wobulated home-theater displays.
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