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Author Topic: Help playing 4K content. Carsten Kurz Film God Posts: 4340 From: Cologne, NRW, Germany Registered: Aug 2009 posted 06-06-2015 05:59 AM                     This moving animated checkerboard pattern shows that the Doremi IMB decodes 4k only up to a certain picture complexity - one can see the full 4k checkerboard up until about half of the screen is filled - then it flashes briefly - and switches to 2k completely. https://dl.dropboxusercontent.com/u/5582554/4K-checker-dissolve_TST_F_XX-XX_NS_4K_Carsten_20150604_OV.zip It's not an input datarate issue, as the frame sizes are actually quite small, far from even the normal 250MBit/s rate (and 4k IMBs need to be HFR capable anyway at much higher bandwidths). So, small patches of 4k checkerboard can serve as a '4k decode indicator' for the whole image. A real world test would need to use typical, yet detailed, 4k flat images with a small patch of the 4k checkerboard as an insert. If the checkerboard is visible, this issue is probably not critical in considering the Doremi IMB as 4k capable. Remains the question wether this is just a decoding flaw with this particular pattern, which could be solved with a firmware update for the Doremi IMB, or wether it's a general weakness with the Doremi IMB. I'll see if I can prepare a test sequence with real cinematic images. Aside from that, it has been confirmed that the Doremi IMB is not able to decode 4k at all if the DCP has been encoded with the OpenJPEG encoder, which is used by all free DCP creation software like DCP-o-matic, OpenDCP, etc. There seems to be a misinterpretation of the resolution layer numbering. The examples above have been created with the Kakadu encoder. Thanks to Stéphane for additional testing. He has one of those rare setups with a Sony SRX-R320 served by a Doremi + IMB-SA - and that Doremi IMB has the same issue. At least the XCT-M10 in Sonys SRX-R515/510 does neither have the 4k checkerboard nor the OpenJPEG issue. Don't know yet for the LMT300. - Carsten  |  IP: Logged Marco Giustini Film God Posts: 2713 From: Reading, UK Registered: Nov 2007 posted 06-06-2015 06:33 AM                     Fantastic! That would explain why my framing chart is decoded properly, it is quite simple with a few area with detailed focusing targets. Unbelievable. I am curious to check a few things on my next 4K machine with Dolby server, I noticed that my 2K framing chart was not scaled perfectly, I could see sort of 'ghosting' lines where colours were changing. Being a 2K to 4K scaling, it should have been harmless. When I'm back to the Doremi install I will try comparing the ICP scaling to the Doremi scaling. Thanks Carsten!  |  IP: Logged Kirk Futrell Film Handler Posts: 95 From: Nashville, TN / U.S.A. Registered: Nov 2008 posted 06-10-2015 04:24 PM                        quote: Carsten Kurz Aside from that, it has been confirmed that the Doremi IMB is not able to decode 4k at all if the DCP has been encoded with the OpenJPEG encoder, which is used by all free DCP creation software like DCP-o-matic, OpenDCP, etc. Before we say it is confirmed, I would like to add that we did play your OpenJPEG version of the 2Kvs4K checkerboard that is primarily blank and the 4K did work with our Doremi IMB/Barco. So it appears that its not an OpenJPEG thing, but a strange complexity of the image with either the lines test or the checkerboard. Carsten and I are trying to come up with some real world tests that include a small 4K checkerboard inside of 4K images or 4K video. So the questions continue.  |  IP: Logged Carsten Kurz Film God Posts: 4340 From: Cologne, NRW, Germany Registered: Aug 2009 posted 06-10-2015 04:37 PM                     Wow. That' even more strange... There is a bit of a mystery about the resolution layers in the J2C that are created by OpenJPEG and Kakadu - OpenJPEG creates 6 Layers, Kakadu 7. The highest would normally be the 4k layer in 4k J2Cs. So there seems to be room for misinterpretation. One would think that the DCI J2C profiles rule this out. So far I am not sure wether this is an OpenJPEG or a Doremi issue. I will have to prepare more test sequences to find out. Moving images are not needed, because J2C is intraframe, there are no dependencies between subsequent frames as far as the decoding is concerned. Of course there could be things like buffering etc. that are not strictly related to decoding, but could still cause issues within a specific image sequence. Also, it is not easy to create real demanding 4k footage. The fact that you have a 4k camera doesn't mean it will deliver the kind of footage that can challenge the IMB they way the checkerboard or line patterns do. That said - my opinion is that you should relax a bit - the tests show that your system is configured properly and will play 4k in general. If the flashing we have seen always occurs when the IMB falls back to 2k (and/or back to 4k), we would have heard about that issue more often, as that would render the Doremi IMB useless for 4k operation. So for now it is safe to assume that the Doremi IMB will play 4k MOST of the time (or never ) . Wether there are other encoder dependencies, I don't know. Kirk, you could indeed try to encode another 'small patch' pattern test with your OpenDCP. - Carsten  |  IP: Logged Kirk Futrell Film Handler Posts: 95 From: Nashville, TN / U.S.A. Registered: Nov 2008 posted 06-10-2015 05:00 PM                        quote: Carsten Kurz That said - my opinion is that you should relax a bit - the tests show that your system is configured properly and will play 4k in general. If the flashing we have seen always occurs when the IMB falls back to 2k (and/or back to 4k), we would have heard about that issue more often, as that would render the Doremi IMB useless for 4k operation. I just got back from the beach, I'm done relaxing . I'm NOT starting up a class action law suit, I'm just curious and appreciate all of your help. There are still a couple of things that I am curious about. When we play the 4K DCP that is entirely filled with the checkerboard, I don't see any flashing it just plays from 2K from the beginning, that being said maybe the flashing is occurring in the black before the image begins playing and I can't see it. So another good test might be a reverse of the one you made that starts out with all checkerboard and then slowly blanks out the image until gone. This would make sure that the image that has been deemed too difficult to play in 4K and downconverted would not prevent the entire playlist item from playing in 4K. What I am worried about is that maybe some content is too difficult to play in 4K and I would never know it, since I have no 2K version to compare it with. The server/IMB might make that decision at the beginning of the film and not try 4K on that clip again. The reason I worry about this is because I have very closely examined 4K DCPs in a 4K playlist vs. the same film in a 2K playlist and cannot spot the difference, even when using a camera upclose to the screen and taking a photo so that I can visually compare the 2 side by side. We can continue this conversation off forum, but I wanted to clear up the openJPEG 4K information, as I know the folks who make those DCPs programs work very hard on them, and I don't want to cast a shadow of doubt on those programs.  |  IP: Logged Marco Giustini Film God Posts: 2713 From: Reading, UK Registered: Nov 2007 posted 06-10-2015 05:51 PM                     I've heard that some 4K movie are just 2K upscaled. Marketing. Get a good RED 4K test clip and play it back in 2K. You should see the difference - even though I never tried to do so.  |  IP: Logged Carsten Kurz Film God Posts: 4340 From: Cologne, NRW, Germany Registered: Aug 2009 posted 06-10-2015 06:11 PM                     Kirk - the problem with comparing 4k vs 2k on a 4k projector is - you are NOT comparing 2k vs. 4k, but upscaled 4k with 'real' 4k. It IS hard to see a difference between the two. If you'd REALLY compare 2k vs. 4k, you would see four 4k Pixel building a single 2k Pixel in a 2*2 cluster. You WOULD see that difference. So, 4k projector and 4k IMB/decoding stack up on each other. And in my opinion the 4k projector is the more important part in that pair, because the 4k pixel raster and the upscaling makes the 2k pixel raster of 2k systems invisible for the audience. - Carsten  |  IP: Logged Carsten Kurz Film God Posts: 4340 From: Cologne, NRW, Germany Registered: Aug 2009 posted 06-11-2015 05:39 AM                     Stephane confirmed the blanked test pattern works also in the OpenJPEG variant on his DoremI/Sony combo. Could be that the Doremi IMB simply drops to 2k with OpenJPEG content earlier than with Kakadu encoded (it's a known fact that Kakadu compresses to smaller files - but again, it is not a datarate issue, even the full screen files are well within the conservative 250MBit/s boundary, and the IMB should support up to 450MBit/s). More testing ;-) this time, also with wrapping back to demonstrate wether the IMB will recover to 4k from temporary 2k fallback. - Carsten  |  IP: Logged Peter Castle Expert Film Handler Posts: 220 From: Wollongong University, NSW ,Australia Registered: Oct 2003 posted 06-11-2015 08:32 AM                     I've tried Carsten's moving animated pattern. Our GDC2000AR/NEC3240 still generates grey every step of the way. Am worried.  |  IP: Logged Carsten Kurz Film God Posts: 4340 From: Cologne, NRW, Germany Registered: Aug 2009 posted 06-11-2015 08:44 AM                     This this one as well: https://dl.dropboxusercontent.com/u/5582554/4k_TEST_Flat_BLANK_OJPEG.zip But maybe it's a setup issue in your case. And really make sure your system is focused exactly to the point. It doesn't need much to miss 4k detail, depending on projected size, lens quality and focus setting. - Carsten  |  IP: Logged Kirk Futrell Film Handler Posts: 95 From: Nashville, TN / U.S.A. Registered: Nov 2008 posted 06-12-2015 05:37 PM                        It's confirmed that the IMB will flash the image and recover to 4K from 2K as the checkerboard pattern disappears from the screen in sections going to blank. Thanks Carsten, I will pass this new info on to Doremi/Dolby.  |  IP: Logged

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