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This topic comprises 5 pages: 1 2 3 4 5
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Author
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Topic: Help playing 4K content.
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Carsten Kurz
Film God
Posts: 4340
From: Cologne, NRW, Germany
Registered: Aug 2009
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posted 06-03-2015 05:30 AM
Axel: Nice test-chart, I'll give that a try, too, just for the fun of it.
To make this a bit easier now with all these DCPs floating around this thread - I created two more ;-)
This time, their checkerboad patterns have additional text to see which encoder was used.
https://dl.dropboxusercontent.com/u/5582554/4kCheckerFlatOpenJPEG.zip
https://dl.dropboxusercontent.com/u/5582554/4kCheckerFlatKakadu.zip
Axel - can you test these two as well on the NEC/IMB combo?
Also, anyone trying this - please make sure your DLP is focused properly, and if possible, try to zoom into wide as much as possible to enlarge the pixel grid as much as possible. On small screens with a bad lens, shaking, or bad focus, this pattern can easily get fuzzy. You will also most probably have to step close to the screen, or use binoculars from the booth.
- Carsten
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Carsten Kurz
Film God
Posts: 4340
From: Cologne, NRW, Germany
Registered: Aug 2009
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posted 06-03-2015 12:01 PM
Interesting hunt for 4k this is ;-)
Axel - could you please download these last two DCPs from the top of this page, one made with OpenJPEG, one with Kakadu, and compare? Both will show the encoder used on screen.
I tested ALL 4k DCPs posted in this thread today on our Sony 515, and they resolved 4k, no doubt. I zoomed the flat image out to 12m (our normal flat width is 7.20m) - even then, a pixel is only 3mm wide. You need to check focus thoroughly to actually see the checkerboard pattern, no way to do this right from the booth.
Stéphane suggested that OpenJPEG has the resolution layer numbering wrong, which could make some media blocks to use the wrong (2k) layer for 4k. He also supplied metadata to me to prove this. If true, obviously, the Sony 515 media block doesn't fail on this. But maybe the older LMT300, Doremi, etc. does? You need to play both an OpenJPEG AND Kakadu encoded DCP to verify this.
This is a photo I took today from Kirks original 4k line pattern, projected onto a white paper to get rid of the screen perforation:
https://dl.dropboxusercontent.com/u/5582554/4k_lines_sony515.jpg
(yes, this was a spot with perfect convergence - it's not like this everywhere ;-)
I also created a full black background with single white 4k pixels evenly distributed over a flat screen to see how J2k/the Sony would cope with it. Those single pixels were all visible in full white, none blurred, colored, or filtered away, aside from the obvious convergence issues in parts of the screen. The max convergence error for our machine is around 1-2 perf hole diameters of our screen, and only horizontal, on the right part of screen. I prefer to average convergence out towards the middle first, then balance sides. Didn't travel much since the installation anyway.
I also projected a full-screen 50% grey to make sure I wasn't simply mistaking the SXRD pixel grid with the checker-board pattern, but honestly that can't happen on a Sony anyway since the SXRD pixel shape is so different. 50% grey was simply grey, with only very low contrast lines visible.
- Carsten
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Carsten Kurz
Film God
Posts: 4340
From: Cologne, NRW, Germany
Registered: Aug 2009
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posted 06-03-2015 03:47 PM
As long as we are not going into low contrast lens MTF or shaky Barcos, these machines can be considered 'digital' displays, that is, 2k or 4k containers are displayed 1:1 on screen (unless scaling mode is activated). Lines per something is an analog measure. It doesn't make sense here. Kirks setup quite obviously has no problem in resolving detail, as the internal test bitmaps of his Barco clearly show his machine is able to display a 4k raster. Just when it comes to his media-block, it unexpectedly drops to 2k.
This is a Sony 515 screen-photo of the Belcourt Test-DCP that Kirk linked to earlier in this thread. The one with horizontal and vertikal lines and checkerboard at *1,*2,*4,*8 pixel spacing from left to right.
It's the upper intersection between 1* and 2* spacing, between vertikal lines and checkerboard. It resolves all of these features. You can see our standard perf screen at the sides.
https://dl.dropboxusercontent.com/u/5582554/belcourt.jpg
As you can see on the upper left qudrant of that A4 paper held in portrait orientation, around 34 vertical b/w lines cover around 10cm of paper width. That breaks down to around 3mm per projected imager pixel, and is compliant with the 12m projection width at 4096pix resolution with the lens at it's 1:1.90 (wide) setting.
Next is simply a 'real' 50% grey taken at roughly the same distance:
https://dl.dropboxusercontent.com/u/5582554/sony4k_grey.jpg
(pretty boring, except for my trigger finger shadow)
- Carsten
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Carsten Kurz
Film God
Posts: 4340
From: Cologne, NRW, Germany
Registered: Aug 2009
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posted 06-03-2015 04:15 PM
Yes, that's what Kirk want's to see - on a 2k system (no matter where that bottleneck is - media block or projector/imager), the leftmost part will be 'grey' because the 4k alternating b/w pattern is downsampled to a 2k solid grey. Or, if Stéphane is right, with OpenJPEG encoded DCPs, some mediablocks do not even touch the 4k resolution layer (a J2k specific), with more or less the same result.
On 4k end-to-end systems, that left part should be lines, checkers, lines. His 4k media block + 4k Barco should be able to render it that way - but for unkown reasons, it doesn't, although Kirk seems to have checked all config options that deal with this.
The 2*, 4*,8* segments should be rendered 1:1 by every current DCI system, 2k or 4k.
Yes, in theory it could be other scaling factors involved, as from 4096 to 3996, but these are not common to be configured on these systems, and would leave different feature artifacts. And, no matter what scaling factor it actually is - Kirk says he has disabled all scaling and downsampling, he want's to achieve a 1:1 projection, as DCIs intention is for both 2k and 4k.
- Carsten
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Kirk Futrell
Film Handler
Posts: 95
From: Nashville, TN / U.S.A.
Registered: Nov 2008
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posted 06-03-2015 11:50 PM
quote: Carsten Kurz
This time, their checkerboad patterns have additional text to see which encoder was used.
Carsten - I forgot to tell you that I tested the openJPEG and the Kakadu DCPs and they both show up as gray images on screen, that was actually while a Doremi technician was logged in making sure everything looked right on the equipment setup end. Although one of the images may have been ever so slightly less dark.
ALso, can you post or PM me a link to the all black with white spots DCP, I would like to see what happens with that one
When we play the test DCP we made that shows 1,2,4,8 pixels (the "Belcourt Test", I hope that name sticks, and that the test is proven useful!), the area with 1 pixel widths is gray, and the others show up correctly.
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