07:07:46 RRSAgent has joined #hdr 07:07:46 logging to http://www.w3.org/2015/10/28-hdr-irc 07:07:52 rrsagent, make logs public 07:08:04 Meeting: High Dynamic Range breakout, TPAC 2015 07:08:05 scribe: nigel 07:08:13 chair: Mark Watson 07:09:04 markw has joined #hdr 07:09:07 skim13 has joined #hdr 07:09:10 present+ wdh 07:09:11 present+ markw 07:09:17 akitsugu has joined #hdr 07:09:18 present+ nigel 07:09:25 Shijun has joined #hdr 07:09:32 present+ skim13 07:09:32 present+ olivier 07:09:57 markw: This seems like a topic that hasn't been discussed much in W3C. 07:10:08 ... There may be people here who are interested but not understand it. 07:10:18 oonishi__ has joined #hdr 07:10:21 shimizu3 has joined #hdr 07:10:26 ... Is there anyone here who is not familiar with High Dynamic Range (HDR) and 07:10:31 ... Wide Color Gamut (WCG)? 07:10:48 group: [would like the introduction] 07:10:58 markw: Presents slides 07:11:15 ... [We've had more resolution and framerate, now looking for 'better pixels'] 07:11:27 ... HDR is about luminance, WCG is about colour range. 07:11:52 ... [slide with london bus] This isn't the real colour of a London Bus. 07:12:20 ... [Luminance slide] Luminance is measured in candela / metres squared or nits 07:13:06 ... range of perception is much wider than what SDR TV and HDR TV cover. 07:13:21 ... HDR is much bigger than SDR - the brights are brighter and the darks are darker and 07:13:30 ... more detail can be viewed in the dark and light regions. 07:13:58 ... [Slide showing colour gamut] We take 3 points on the colour diagram and all the 07:14:15 ... colours we can represent are inside the triangle that they define. Shows Rec709 as 07:14:34 ... the smallest triangle, Rec2020 as the biggest, some in between. There aren't many 07:14:49 ... displays that can show the whole 2020 colour space. We can signal and encode 07:15:05 ... colours in that space but the device will shrink those down. Lasers are needed right now 07:15:10 ... to show the whole gamut. 07:15:31 ... [Slide showing 3d picture of WCG and HDR] We talk about colour volume now, 07:15:45 ... representing the entire range of colours and brightness that we can encode. 07:16:06 ... [Slide, example from Dolby with picture of flowers] All of the red points are those that 07:16:31 ... fit in the color volume, and the blue ones are outside it. An ordinary picture has 07:16:40 ... colours in it that are way outside the range that we can represent today. 07:17:08 Bill: There's a lovely example of why this matters. Two NY Giants jerseys. A 30 year old 07:17:22 ... one and a 10 year old one. Part of their brand identity is the exact colour that they 07:17:39 correii has joined #HDR 07:17:47 ... use. If you're limited to RGB or Rec709 you cannot accurately and reliably capture the 07:18:00 ... colour that is part of the brand identity. So there's a commercial gain to doing this 07:18:03 ... more accurately. 07:18:24 XXX: Cinema displays can show a bigger volume than TVs. When you go through the 07:18:45 ... process of making a film for cinema and TV you force the colour grader to make 07:18:48 ... limiting choices. 07:19:01 markw: For video and contribution display the introduction of HDR and WCG affects all 07:19:01 s/XXX/wdh/ 07:19:21 ... the steps in the chain. Video cameras can capture a lot. On the production side 07:19:42 ... lights need to be considered too. In Post production color grading and reference monitors 07:19:52 ... need to be changed. They need to learn how to use the new tools. 07:20:08 ... In Encoding and Delivery you need more bit depth (10 bit), a different transfer function 07:20:40 ... (that maps from a 10 bit number to luminance value), and colour space. 07:20:56 ... In displays there's lots of new technology in consumer displays - LEDs with local 07:21:14 ... backlights and dimming, OLEDs etc. "Tone mapping" is important - the fact that a 07:21:16 Dewa has joined #hdr 07:21:29 ... signal that you've encoded has been created for a reference master display. No 07:21:40 ... consumer displays have the same brightness as the master display. Tone mapping 07:21:49 ... is far from straightforward, to map from one to the other. 07:22:06 ... [Web Platform Issues]. Questions for the Graphics plane and the Video Plane. 07:22:20 ... There will be devices that support HDR for video but not for graphics. In both cases 07:22:32 ... we have both an encoding problem and a discovery problem, to discover display 07:22:46 ... capabilities. There's also the question of image formats for HDR images. 07:23:06 ... There's video capture on the web platform too. 07:23:18 YYY: for webcam if you have strong backlight, e.g. for video conferencing, it is very 07:23:25 ... difficult to get a good picture. 07:23:33 wdh: Consumer capture is really interesting. 07:23:53 markw: Codec and display capabilities are two independent things. Our current APIs 07:24:09 ... are quite good at codec discovery - MIME types with codecs, levels, profiles etc. 07:24:23 ... But just before I have an HDR codec does not mean I have an HDR display. 07:25:32 nigel: There are also questions around compositing graphics on video. Plus there was 07:25:47 ... a liaison from ATSC to TTWG asking about how to deal with HDR and WCG given that 07:25:53 ... timed text formats only support sRGB. 07:26:29 markw: Is there a requirement around compositing? 07:26:38 wdh: It feels like an implementation thing. 07:26:51 bill: Don't you need to specify an EOTF. 07:27:11 pierre: If you composite SDR over HDR then there are circumstances when you might want 07:27:35 ... to boost or darken the graphics compared to the image. Using an 80 nit max for 07:27:48 ... sRGB might be too dark or too light depending on the image. 07:28:00 markw: So you want the application to have a brightness control? 07:28:08 pierre: Give the author the ability to specify that. 07:28:13 markw: That's what I meant. 07:28:32 bill: Having a brightness knob on the entire plane might be an interim solution. 07:28:50 pierre: You don't want to have to backport HDR into CSS, SVG, TTML etc. Also if you have 07:29:04 ... an existing library of SDR content does it make sense to make an HDR version of the 07:29:06 ... same content? 07:29:25 bill: Sometimes yes, sometimes no, depending on the commercial motivation. 07:29:59 dsinger has joined #hdr 07:31:26 nigel: One thing that's really easy to specify is that sRGB values must not be interpreted 07:31:44 ... as HDR values, because that would result in full intensity values being painfully bright. 07:32:10 ... (accepting that the relative brightness might need to shift up and down). 07:32:40 dsinger: Actually displays are already a bit brighter than sRGB peak white (80 nits). 07:32:51 markw: You might have to set the brightness control right. 07:33:05 wdh: You've identified these are interesting problems. Are there others? 07:33:23 YYY: Do you mean the graphics plane as encrypted? 07:33:50 markw: I'm talking about the display. Televisions have this problem particularly. 07:33:59 ... They have two separate pipeline processes for video vs graphics. 07:34:19 bill: What we've seen is that they do some mapping. 07:34:37 dsinger: There's another issue. In the world of audio we've had to manage range to 07:35:07 ... avoid hurting people's ears. In the pictures we may need to do something similar. 07:35:20 wdh: In the UK there are requirements about that. 07:36:15 group: discusses the calm act and the need to make content accessible. 07:36:37 wdh: The brightness issue is valid - just dealing with ambient light feels like an implementation 07:36:42 ... as opposed to a standards thing. 07:36:49 bill: The tone mapping is outside the standards space. 07:37:01 markw: A possible technical area that might require work is: You have a site with HDR 07:37:23 ... graphics and some adverts. Should the adverts be able to constrain the page peak brightness? 07:37:38 bill: It's not just peak brightness - the appearance isn't just defined by the peak. 07:38:02 nigel: Are you talking about dynamic adjustment of the whole composited plane? 07:38:44 markw: I'm talking about content in an iframe changing the appearance of the main content. 07:38:57 dsinger: Like a dark goth page that's spoiled by a bright pink advert. 07:39:08 nigel: Isn't that a content provider issue? 07:39:23 markw: Yes you could request that only adverts conforming to a particular profile are served. 07:39:38 ... If the web platform could in some way cap or constrain the brightness of content 07:39:43 ... that could be useful. 07:39:54 bill: An argument in favour is the health safety. 07:40:06 markw: That would argue for some kind of transformations in the CSS realm. 07:40:12 wdh: That's interesting. 07:40:25 markw: The immediate thing that's of most concern is video display capability discovery. 07:40:37 ... I thought at some point that CSS was the right place to discover this, but in realising 07:40:58 ... that the graphics capability and the display capability might be different I think that 07:41:04 ... they're separate. 07:42:15 nigel: So if you discovered you had a sRGB display or a 2020 display what would you do? 07:42:28 markw: You'd choose which content to download and show. 07:42:40 nigel: Why wouldn't you apply the transformation locally to the same content? 07:43:07 dsinger: Some high value content is carefully graded to be optimal for a particular display. 07:44:07 wdh: So if you signal a particular codec and you're casting it to the TV, that doesn't 07:44:24 ... allow enough information about what exactly to put on the page. Plus the video window 07:44:33 ... might be on a monitor or dragged over to a TV. 07:44:48 dsinger: You can ask 'do you have a 10 bit codec' but that doesn't tell you anything about 07:45:09 ... the color space. We've traditionally thought of the display capabilities as being 07:45:13 ... independent of the codec. 07:45:55 markw: I've even wondered if you might have a situation where you have an HDR display 07:46:10 ... but somehow the content that you fetch is SDR. 07:46:30 YYY: You might have a problem where the display falls back to the lowest common denominator space. 07:46:43 markw: You mean if you were compositing graphics on video? 07:46:45 YYY: Yes. 07:47:02 markw: So if we thought that compositing SDR graphics on HDR video would cause the 07:47:10 ... whole thing to drop down to SDR we wouldn't do that. 07:47:32 markw: From our company perspective everything has to all work together and look 07:47:43 ... right for the product. A question in this group would be, for the web platform, if 07:47:53 ... we are going to introduce HDR, should we place the same requirements on it. 07:48:08 ... You're not allowed to advertise HDR capability unless you can successfully composite 07:48:13 ... these things together. 07:48:27 wdh: Set top boxes have a hard problem - multiple in, multiple out. It's even harder than 07:48:36 ... for TVs. We're doing it but it's ugly. 07:49:40 dsinger: I've seen an example where negative primary values can be used to go outside 07:49:43 ... the color gamut. 07:50:01 markw: +1 to just specifying a new color gamut. 07:50:23 dsinger: Practically, a media query in CSS needs to come up with a boolean answer. 07:50:40 ... I'm wondering if asking "What %age of the sRGB or 2020 triangle do you claim to be 07:50:51 ... able to render?" then maybe that would work given that the triangle is normally 07:51:03 ... reasonably well centred, so you could get close enough that way. 07:51:19 pierre: The challenge is that there are lots of other parameters, not just color volume, 07:51:36 ... but also max and min luminance. What about querying specific formats from the display. 07:51:44 ... rec709, BT2020 etc. 07:52:10 markw: I think that you can assume that if a display can understand the color values in 07:52:17 ... 10 bits then it can display them. 07:53:31 bill: boolean for colorspace is probably ok 07:55:09 billh: seeing that luminance threshold depends on device : OLED vs LCD etc. 07:55:27 ... 400nits OLED may be ok, but 700 for LCD 07:56:07 dsinger: displays will improve over time, unlike the static situation we believed we were in before 07:57:17 markw: We're near the end of the session. We should try to input this to the CSS WG 07:57:28 ... as a starting point to generate some more discussions. I don't have any bright ideas 07:57:38 ... about indicating the display capability. 07:58:12 markw: Is that a category - do still images go with the video capability or the graphics capability? 07:58:43 dsinger: Is the TV rendering it all? 07:58:55 pierre: Captions - the television composites them on the video. 07:59:04 ... What's the process in CSS WG? 07:59:19 markw: The process is first find a browser who's interested and then take it to the group! 07:59:37 dsinger: I'm going to talk to my guys about this and do some experiments. 07:59:56 pierre: Do you think they'd be interested to specify colours differently or assume that 08:00:08 ... CSS will continue to render to sRGB or both? 08:00:19 dsinger: CSS will need to be able to represent colours outside the sRGB plane. 08:00:41 nigel: Then you have the reverse problem - what do you do if a colour outside sRGB 08:00:49 ... needs to be rendered on an sRGB display? 08:00:52 dsinger: yes. 08:01:01 rrsagent, make minutes 08:01:01 I have made the request to generate http://www.w3.org/2015/10/28-hdr-minutes.html nigel 08:01:18 dsinger: Just to frighten you, what if someone just offers full ICC colour profile? 08:01:31 pierre: ICC has the concept of diffuse white, which PQ doesn't have. 08:01:35 markw: What is diffuse white? 08:01:49 pierre: When you define an ICC colour profile you have to define diffuse white. Today 08:02:00 ... most implementations match that to their maximum white luminance. An example 08:02:21 ... is a HDR PNG with an embedded ICC profile that specifies diffuse white at 100 nits. 08:02:33 ... Most applications just clip everything above 100. 08:02:50 Action: markw to forward these minutes to the CSS group! 08:03:02 rrsagent, make minutes 08:03:02 I have made the request to generate http://www.w3.org/2015/10/28-hdr-minutes.html nigel 08:03:41 scribe: markw 08:03:43 rrsagent, make minutes 08:03:43 I have made the request to generate http://www.w3.org/2015/10/28-hdr-minutes.html nigel 08:13:16 oonishi has joined #hdr 08:14:33 nigel has joined #hdr 08:16:50 akitsugu has joined #hdr 08:38:03 dsinger has joined #hdr 09:55:13 skim13 has joined #hdr 10:54:15 skim13 has left #hdr