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4th August 2020, 19:08 | #21 | Link | |
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From my experimentation, HLG can look really good on SDR (with 709 color) as long as: 1. The player is HLG-aware and tone maps accordingly. 2. The reference white level for the picture is at 75% signal strength. The Avengers came out looking really good after using the "MARVEL" text at the beginning to set reference white. I'll post an Imgur link when I'm off work. Screenshots: https://imgur.com/a/9nEZhlR Last edited by wswartzendruber; 5th August 2020 at 02:03. |
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9th August 2020, 16:58 | #22 | Link | |
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Great colors. Can you upload some PQ video and therefore HLG video after your PQ to HLG Converter? Last edited by VictorLS; 9th August 2020 at 19:05. |
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9th August 2020, 22:21 | #23 | Link |
Derek Prestegard IRL
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I find it interesting that such a significant technical decision (PQ vs HLG) appears to have been made solely based on concern for such a small group of 4K early adopters with UHD SDR BT2020 displays.
If you are okay with giving that small cohort FHD SDR 709 along with all the other people with legacy HDTVs, then you can just have that legacy feed and a pure HDR feed. You could make it HLG, sure, but there's a lot of very good HDR TVs that don't support HLG. That seems like a much more important cohort than the tiny number of UHD SDR TVs. Understood that production and acquisition must be done in LOG or HLG, fine, but what you COULD do is distribute in PQ that's compatible with Dolby Vision Profile 8.1, HDR10+, and HDR10. This is compatible with every single HDR TV ever manufactured. This is all doable today for VOD, and I think soon for live (tho not sure live HDR10+ is even a thing? Doesn't seem possible to me). Even if it's just HDR10, that works literally everywhere AFAIK. Show me a single HDR TV without support for HDR10. For live via traditional satellite distribution where transponder capacity is so expensive, this seems like the ideal HDR WCG solution to me. I guess, it comes down to -- who do you screw over? Someone with an old UHD SDR display, or someone with an earlier UHD HDR display that is excellent other than its lack of support for HLG? For example, I bought an LG B6 a few years ago. It's a great TV still to this day, but it only supports HDR10 and Dolby Vision. Do you screw me over, or the guy with a super expensive first generation UHD TV who, let's face it, has probably already upgraded because he wants HDR! Last edited by Blue_MiSfit; 9th August 2020 at 22:40. |
9th August 2020, 23:47 | #24 | Link | ||
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Yep, 'cause VOD is a completely different thing, but who would ever encode the same movie or TV Series twice once it has been encoded in HLG already? No one (just like no one would do it in PQ only as playout channels are still in HLG). In other words, it can be done, but no TV Studio does it 'cause it would require two encodes, two mezzanine files and two QCs unfortunately... (but services that are VOD-only and not owned by a TV Company could potentially do it and are doing it already I think). Derek, I don't know if I can ask you directly out of curiosity, but you work for big D, is your + offer in PQ with HDR10? HDR10+? Dolby Vision? HLG? SDR only? Are you dragged behind by linear channels as well? Quote:
lol your TV would still recognize the feed as BT2020nc SDR and you would see the same "just barely watchable" feed someone with an old BT2020 SDR UHD TV would see, so none is screwed (or both of you are, depending of the point of view hahahahahaha) Last edited by FranceBB; 10th August 2020 at 09:10. |
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10th August 2020, 00:26 | #25 | Link | |
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https://www.bbc.co.uk/rd/projects/high-dynamic-range Last edited by wswartzendruber; 10th August 2020 at 00:30. |
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10th August 2020, 21:06 | #26 | Link | |||
Derek Prestegard IRL
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I don't work on D+, but I know the service offers SDR, HDR10, and Dolby Vision. There's not currently any HLG or HDR10+ support. I DO work on Movies Anywhere, which supports the same formats. Last edited by Blue_MiSfit; 10th August 2020 at 21:19. |
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10th August 2020, 21:09 | #27 | Link | |
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Last edited by Blue_MiSfit; 10th August 2020 at 21:13. |
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11th August 2020, 16:06 | #28 | Link | |
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My background is that I didn't get into HDR at all until HDR10+ was already a thing. So I'm very late to the game. Research and study (various docs from the ITU and BBC) revealed that for some reason, the industry had chosen to begin distributing content in a system that used absolute brightness coupled with metadata. Distribution to end users inherently entails differing viewing environments, which metadata doesn't address at all. If you are going to point at HLG and call its rationale FUD, then I want you to defend distributing content in PQ instead. What advantages do you receive? |
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12th August 2020, 00:08 | #29 | Link | |||
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(Since you specified it, I specified it as well; better safe than sorry xD) Quote:
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Jokes aside, non-static metadata on a linear channels with contents played by a playout port, encoded live and aired can be a pain in the... *forbidden word :P * so I understand why some decision were taken in the past (along with all the other reasons I stated before). |
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12th August 2020, 01:47 | #30 | Link | |
Derek Prestegard IRL
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To be honest, I was just trolling a little I don't have any hard evidence whatsoever that HLG is inferior to PQ, or that using PQ offers some advantage over HLG --- aside from my unchallenged point that PQ offers wider device compatibility in the rec2020 case, especially on early HDR TVs. Thankfully, almost everyone seems to support HLG on modern devices now from what I can tell. The notable exception is Roku set-top boxes (distinct from TVs with Roku's software like TCL). This is a ___HUGE___ market in the US, actually, and is the single biggest cohort for 10 foot viewing here, so that's a major factor. Does anyone know of any other new devices that support a PQ format but not HLG? The creatives I've spoken with with prefer PQ, and are in general fans of having an absolute signal that is display referenced. Their standpoint is that with relative luminance, for example, HLG can misrepresent contrast. However, I absolutely do feel the pain of needing to worry about a 1000 nit grade or a 2000 nit grade, and worrying about how mapping these to a 4000 nit display is not defined, even if there are a lot of pretty good solutions to map either of those examples to a 600 nit display, for example. I can see the draw of sticking to a relative, scene-referenced signal, and having a reasonable degree of faith that it will display nicely on a broad swath of HDR WCG displays without needing to futz with metadata. My point was that, to be totally pragmatic, many displays totally ignore metadata and just do their own thing. So like, I wouldn't be surprised if everything would mostly be fine if we just had no metadata at all (other than the transfer, primaries, and differencing flags to identify content as PQ or HLG, and 709 or 2020, of course!) hence the "metadata FUD" troll Personally I still prefer Dolby Vision Profile 5 for a number of reasons, but that's getting OT pretty fast! Last edited by Blue_MiSfit; 12th August 2020 at 01:54. |
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12th August 2020, 07:22 | #31 | Link | ||
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1. Study spec sheets. 2. Write code. 3. Write tests for code (checking math values). 4. How does it look on SDR through a HLG-aware (tone mapping) player? Nailing #4 is all about figuring out a good reference white value (in nits) for the PQ source material. That's everything. It'll look too dim if that's set too high and it'll look completely clipped if it's set too low. I think I've said this before, but I am going to say it again and again because of how important it is. Nailing #4 is a massive step in having HLG content that can play back on 709 devices. Assuming of course, you have a competent color+tone mapping player, which even the open source community has access to. Quote:
FOR FUN: Here's an attempt at Rogue One on VLC (SDR/709 tone mapping) with reference white set too low. https://imgur.com/gallery/AyQW7Pg EDIT: I need to watch Rogue One again just to pick out a good reference white scene. That movie is really throwing me around. Alita: easy Avengers: easy Age of Ultron: slightly difficult Rogue One: "Ohhhhhhh no! You are NOT converting me to HLG!!!" EDIT: I wonder if I could build a sort of predictive model that analyzes every pixel of every frame and then computes an approximation for where reference white should be... Last edited by wswartzendruber; 12th August 2020 at 07:45. |
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13th August 2020, 21:04 | #33 | Link | |
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In any event, I can compute this stuff myself. And that's what I'm already doing with pqstat. I could have it compute MaxFALL as well, if I wanted. But what I'm really after is reference white and I'm not seeing how MaxCLL and MaxFALL will help with that. By reference white, I mean the border between SDR and HDR brightness levels. |
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13th August 2020, 22:03 | #34 | Link |
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Really?! O_o Leaving aside the 1000 nits, even if they're lower, they should all have metadata and it's actually very important in HDR10 PQ. I would understand HLG .ts files, but not UHD-BD disk with PQ... Are you ripping the original m2ts file? What does ffprobe say? Perhaps it's just MediaInfo not showing them for some reason? I mean, it would be weird for an HDR10 official disk not to have metadata.
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13th August 2020, 22:47 | #35 | Link | |
Derek Prestegard IRL
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16th August 2020, 05:28 | #36 | Link | |||
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I use MakeMKV to remux whatever streams I pick from the disc into Matroska. Quote:
Speaking of which, my friend bought a HDR-capable phone and had no idea. So we sampled Rogue One (my latest attempt) on both our sets side-by-side. And while I didn't notice much difference in luminousity, the color on his was absolutely gorgeous compared to mine. EDIT: Rogue One HLG Screenshots Last edited by wswartzendruber; 16th August 2020 at 17:59. |
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16th August 2020, 22:01 | #37 | Link |
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Well, the remux shouldn't really get rid of the metadata as they're in the video essence itself, so if they put them there, they're still gonna be there after the remux. Anyway, VLC is probably one of the worst players for HDR contents, in fact my choice falls on MPV, especially if you have an SDR monitor. By the way, I actually found the MPV tone-mapping for PQ contents with metadata to be pretty much fine, while it's kinda sloppy for HLG materials without metadata...
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16th August 2020, 22:38 | #38 | Link | |
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You should provide evidence when making baseless claims that impugn others' work. And 'probably'? Is that only on random days or do you roll dice every day to decide?
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When someone resorts to rhetoric we have to question their confidence in their technical arguments. Don't mean to be harsh. Last edited by videoh; 16th August 2020 at 23:00. |
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17th August 2020, 00:27 | #39 | Link | ||
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VLC: https://imgur.com/JktOMOt MPV: https://imgur.com/ky2Kg6k You can clearly see that VLC got it wrong and that it shouldn't really be displayed that way on SDR displays... I gotta say that I don't have it installed anymore, so I don't know whether things improved or not, but I can say that MPV definitely applies the tone-mapping when it has to display HDR on an SDR monitor (and it did it years ago as well, while VLC didn't). Quote:
lol, no problem at all, when I say things they're always based on my own personal usage and on what I found out in my examples, not as "absolute statement" or "dogma". They're definitely open to discussion. So... even if I don't specify anything, always take them as my personal point of view Last edited by FranceBB; 17th August 2020 at 00:32. |
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