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This topic comprises 11 pages: 1 2 3 ... 8 9 10 11
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Author
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Topic: Dolby Cinema
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Bobby Henderson
"Ask me about Trajan."
Posts: 10973
From: Lawton, OK, USA
Registered: Apr 2001
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posted 05-28-2015 11:10 AM
quote: Carsten Kurz
Dolby Cinema currently does not yet have the final Dolby Vision contrast enhancement light engines available. What they are doing different is they use special mastering/grading to deal with their specific brightness/contrast levels, tailored to their specific auditoriums.
That just makes it sound like they're faking it and not really delivering true HDR playback. They're just showing (and charging) customers for a much brighter than usual projected image that is imitating HDR. The folks in movie production and post production might be seeing true HDR, but the customers are not.
It's kind of like someone mastering an music album in 24-bit 96kHz resolution then giving someone a .WAV file or even lossy MP3 downsampled to 16-bit 44.1kHz, yet still trying to claim that file is 24/96 because it was originally mastered that way.
quote: Carsten Kurz
3D DCI is 12bit XYZ just as 2D is. 'Legacy' systems drop to 10Bit 4:2:2 YCbCr only for the transmission part over dual HD-SDI links.
The end result of that bottleneck for anyone watching 3D on a legacy system is they're seeing 4:2:2 and not 4:4:4.
quote: Marcel Birgelen
The system, like many of the more recent Series 2 installs is capable of doing more than 250 Mbit/s. This particular system should be capable of doing HFR 3D in 4K. Compressing this down into 250 MBit/s will get very messy.
Very messy indeed when you look at some of the constraints in how movies have to be encoded in JPEG2000. No interframe compression is allowed. There are limits to the amount of tiling that can be done. Chroma subsampling is indeed a big part of JPEG compression, but if that and use of interframes is off the table then things have to get more severe in other areas. Blu-ray has more tools at its disposal via MPEG-4 AVC or VC-1 with being able to efficiently compress video, plus they're not trying to squeeze something like 4:4:4 video onto the disc. AFAIK, none of the Hollywood movies released on Blu-ray have been "deep color" at all, despite the early hype about deep color capability in Blu-ray.
I find it amazing, or rather alarming, that some 2 hour DCP movie files can show up only 60GB or 70GB in size. Just what are they doing to squeeze the files down that small without breaking any of the rules? I've seen complaints about deplorable video quality in repetory titles on DCP, raising the suspicion the JPEG 2000 imagery was actually sourced from a Blu-ray encode. That's basically re-compressing an already lossy compressed source. Total shit standards of practice.
Now we're going to expect HDR to work within current DCP limits? Or 1080p and/or 4K on consumer electronics platforms? After years of putting up with Lie-MAX hype and a big screen being all that's needed to call something "large format," this just seems like another opportunity for people selling technology to play fast and loose with the truth.
quote: Marcel Birgelen
On the production side of things... I'm not sure if any camera out there is fully capable of recording "HDR" in the full "PQ color space" in a single exposure.
For advertising purposes I don't think they'll use that kind of qualifier. Right a bunch of the hype is centering around how many stops of light certain cameras like the Arri Alexa XT can see (14+ according to the specs page) and what all can be done with that ARRIRAW footage in an uncompressed 16-bit workflow. That's all fine and dandy. Unfortunately the customers in the theater aren't really seeing any of that 16-bit uncompressed goodness. They're paying a lot of money to see a bit reduced approximation of it.
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Carsten Kurz
Film God
Posts: 4340
From: Cologne, NRW, Germany
Registered: Aug 2009
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posted 05-28-2015 03:59 PM
Dolby is not advertising Dolby Cinema as HDR yet. Nor is anyone advertizing HFR, HDR, Dolby Cinema , IMAX Laser etc. using legacy/HD-SDI systems.
If there is someone faking something, it's you because you seem to have no problem to make up issues for endless pages of discussions, but are not even interested in reading free docs that would help you in avoiding your false assumptions.
Okay, unlike e.g. IMAX you are not charging money for your statements, so, at least it's a free ride...
- Carsten
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Marcel Birgelen
Film God
Posts: 3357
From: Maastricht, Limburg, Netherlands
Registered: Feb 2012
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posted 05-28-2015 04:15 PM
quote: Bobby Henderson
Very messy indeed when you look at some of the constraints in how movies have to be encoded in JPEG2000. No interframe compression is allowed. There are limits to the amount of tiling that can be done. Chroma subsampling is indeed a big part of JPEG compression, but if that and use of interframes is off the table then things have to get more severe in other areas. Blu-ray has more tools at its disposal via MPEG-4 AVC or VC-1 with being able to efficiently compress video, plus they're not trying to squeeze something like 4:4:4 video onto the disc. AFAIK, none of the Hollywood movies released on Blu-ray have been "deep color" at all, despite the early hype about deep color capability in Blu-ray.
Keep in mind that even 4K 3D isn't part of the DCI specs just yet. Still, those newer systems, like this Dolby/Christie system and the Barco Alchemy IMBs handle DCP bitrates far beyond 250 MBit/s just fine. I doubt Dolby Vision content will be limited to 250 MBit/s, although it actually might be sufficient for most content actually.
You can mess around with everything obviously, but I do think the absence of interframe compression in the main delivery format for DCI is more of a blessing, because it at least avoids many of those ugly artifacts caused by sloppy executed MPEG compression. Although you could actually get better results when using interframe compression at the same bitrates DCI is using right now, the chances to mess up are also increasing almost exponentially.
quote: Bobby Henderson
I find it amazing, or rather alarming, that some 2 hour DCP movie files can show up only 60GB or 70GB in size. Just what are they doing to squeeze the files down that small without breaking any of the rules? I've seen complaints about deplorable video quality in repetory titles on DCP, raising the suspicion the JPEG 2000 imagery was actually sourced from a Blu-ray encode. That's basically re-compressing an already lossy compressed source. Total shit standards of practice.
Well, yes. It's primarily Warner and their subsidiaries who seem to be keen to compress the heck out of it. Some of their releases could even fit on a Blu-Ray disc... Maybe they pay their "labs" by the gigabyte, or I don't know what their issue is...
The lack of quality in repertoire titles is probably being caused by people not giving a shit and the lack of big budgets behind the project. If it's really the already compressed Blu-Ray which is being used as source, it's indeed piss-poor job, but that's just guessing.
Neither of this really is the fault of the DCI specs though. At 250 MBit/s, you end up at about 110 GByte/hour at the maximum bitrate, which every compliant system is supposed to handle just fine.
quote: Bobby Henderson
Now we're going to expect HDR to work within current DCP limits? Or 1080p and/or 4K on consumer electronics platforms? After years of putting up with Lie-MAX hype and a big screen being all that's needed to call something "large format," this just seems like another opportunity for people selling technology to play fast and loose with the truth.
Well, no. Not really. The color space Dolby Vision it's using, isn't in the DCI specs at this moment. Those DCP limits will most likely eventually be be widened, but it takes time before those specs get ratified. Like I mentioned before, the Dolby Vision content does use 12 bits JPEG2K, but uses a different, logarithmic color space. This logarithmic color space is essentially a form of compression, but I doubt it is really noticeable in the sense of how this is perceived by our vision.
Also, nobody is going to force Dolby to limit the bitrate to 250 MBit/s for their Dolby Vision releases, since their platform can do more already.
For the consumer side of things, you will need custom equipment to make it work and there will be a higher bitrate for Dolby Vision content. It's just that the Dolby Vision data will be delivered as some kind of transform mask as metadata alongside the normal video data. The normal video data will be in a "normal" color space, while the transform mask combined with the "base signal" will yield the image with the wider color space.
I'm not sure if this design will be compatible with a household Blu-Ray player though, as in if it can read and forward the extra metadata alongside the image stream. But you should be able to play those Dolby Vision Blu-Rays (of which there are already a few) on your "legacy" hardware, although without the benefits of "Dolby Vision" obviously.
quote: Bobby Henderson
For advertising purposes I don't think they'll use that kind of qualifier. Right a bunch of the hype is centering around how many stops of light certain cameras like the Arri Alexa XT can see (14+ according to the specs page) and what all can be done with that ARRIRAW footage in an uncompressed 16-bit workflow. That's all fine and dandy. Unfortunately the customers in the theater aren't really seeing any of that 16-bit uncompressed goodness. They're paying a lot of money to see a bit reduced approximation of it.
Sensitivity isn't the only thing important, the actual color filter arrays being used should also be up to the task and I'm not sure we're there yet. Sony is marketing their S-Gamut color system for the CineAlta F55 and F65 for example, which is already a lot wider than e.g. DCI or even printed film. It probably doesn't qualify for "single shot HDR", but continuous improvements are being made on this side of things.
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Bobby Henderson
"Ask me about Trajan."
Posts: 10973
From: Lawton, OK, USA
Registered: Apr 2001
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posted 05-28-2015 11:57 PM
quote: Carsten Kurz
Dolby is not advertising Dolby Cinema as HDR yet. Nor is anyone advertizing HFR, HDR, Dolby Cinema , IMAX Laser etc. using legacy/HD-SDI systems.
Yet HDR is the thing being hyped about it via the Dolby Vision brand name. If they're not specifically saying HDR the implication of a movie being HDR is still there.
quote: Carsten Kurz
If there is someone faking something, it's you because you seem to have no problem to make up issues for endless pages of discussions, but are not even interested in reading free docs that would help you in avoiding your false assumptions.
If you have a problem with something I'm writing please pick it apart with specifics rather than make a blanket statement implying anything I'm writing here at Film-Tech is based on false assumptions.
There is a strong degree of bullshit going on with how digital cinema is advertised these days, especially in the premium screen space where the term "large format" is now a bold faced lie.
It's one thing for a d-cinema theater to make compromises in a standard priced theater. When movie studios, technology companies and theaters start tacking on premiums the customers have every right to question just what value is actually being delivered for those extra dollars. We can thank IMAX for wall to wall movie screens with no masking, regardless of auditorium size. Scope in d-cinema is a travesty; they don't want to deal with the expense of anamorphic lenses, but there's no problem charging theaters and customers a bunch for 3D and a whole lot more than that for laser. Immersive audio looks it may go from being a promising advancement in surround sound to being a meaningless, jumbled mess, but it will at least be "open" -whatever that means to paying movie theater customers.
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