[DCP-o-matic] 4k

I participated in an interesting thread on film-tech that deals with an anomaly of Doremi (now Dolby) IMBs. As far as we found out, the Doremi IMB will not display 4k content when it was encoded with OpenJPEG - that would be true for all open-source DCP creation utilities, like DCP-o-matic, OpenDCP, etc. A guy from france with some programming insight into both OpenJPEG and the Kakadu encoder hinted me towards a possible reason for this - JPEG2000 offers multiple resolution layers, 2k and 4k are one of these resolution layers (smaller ones are there as well). He pointed out that OpenJPEG and Kakadu may use different numbering schemes to express these resolution layers, and that the Doremi IMB may misuse the highest number in OpenJPEG, thereby only selecting the 2k layer instead of the higher 4k layer. As a matter of fact, our Sony XCT-M10 (part of the Sony SRX-R515/510 projectors) does not have that issue, it will display 4k from both OpenJPEG and Kakadu. So far, it is not entirely clear to me wether that is an issue with OpenJPEG/DCI profiles handling, or if it is a flaw in these Doremi IMBs. I have never been a strong endorser of using 4k for your own projects, in most cases, it's not worth the extra memory or compression time. It is actually really hard to create/maintain real 4k value in your source footage. Aside from that, all 4k projectors do a pretty good job in upscaling 2k to 4k anyway. So aside from some synthetical patterns (which actually lead us finding that bug), I see little benefit in creating 4k DCPs. Same is true for using higher J2k bandwidths than 150MBit/s as long as you stay within 24-30 fps content. The second issue is that while testing the 4k behavior of the Doremi and Sony IMBs, we found out that, even when using other J2K encoders like Kakadu, the Doremi IMB can not display complex full screen patterns in 4k - it will drop to 2k as well. We only confirmed this with synthetic checkerboard patterns again, it is not clear how likely this is to happen with any 4k real-life footage. We will conduct more tests to find out about that. The Doremi will not only show complex 4k content in 2k only, it will also create nasty flashing when switching between both modes. So there is a another good reason to not create 4k DCPs if not absolutely necessary. Well, until the first issue is either solved in OpenJPEG or the Doremi firmware, there are little chances that these nasty flashing artifacts turn up with any 4k content created with DCP-o-matic or OpenDCP - simply because the Doremi will not select the 4k layer at all. There is an early J2k viewer contained in the OpenJPEG 1.3 package which is able to detect the different numbering schemes between OpenJPEG and Kakadu. There is also a hint towards it contained in this paper on J2K encoders - even if it doesn't deal with DCI J2C profiles - see tables 1 and 2 on page 3 of this document: http://purl.pt/24107/1/iPres2013_PDF/An%20Analysis%20of%20Contemporary%20JP… Carl, did you ever come across the resolution layer numbering scheme when dealing with OpenJPEG in DCP-o-matic? - Carsten