Re: Help with HLG profile

Hi Craig,

I don’t think there is, yet, a definitive best practice for drama 
production in HDR, but I can venture my own opinions.

I do not think that either PQ or HLG are ideal as a capture/production 
format for drama (including movies). HLG is not ideal because, in a 10 
bit version (and, of course, TV production equipment is currently 
limited to 10 bits) it does not provide sufficient dynamic range capture 
latitude for drama post production. PQ is also unsuitable for drama 
capture for related reasons. PQ is designed so that quantisation levels 
are, just, invisible (again in a 10 bit system) when the signal is 
displayed at its stated luminance. However, for drama production the 
captured signal will be modified during post. For example, the signal 
may be amplified to show more detail in the shadows and blacks (perhaps 
the capture exposure wasn’t perfect, or the content needs to be matched 
with other content). When you amplify PQ you separate the quantisation 
levels. Separating the quantisation levels means that banding, that was 
just invisible originally, now risks becoming visible. For this reason 
PQ also does not have sufficient dynamic range latitude for drama 
capture (you can’t reliably amplify it to make shadow detail more 
visible). I would re-iterate that this applies to 10 bit signals.

If neither PQ nor HLG are ideal for drama capture and production what 
will be used? I strongly suspect that proprietary log formats (slog, 
c-log etcetera, ad nauseam) will be used. The final result being 
rendered to either PQ or HLG as required.

Which is related to you question on the production workflow for the 
World Cup. I think, but please don’t quote me on this, that the workflow 
uses a non-standard proprietary format, which is then converted to both 
PQ and HLG. So, pretty much the workflow I have suggested for drama (but 
with much less post production).

I agree that HLG is a good model for live broadcasts (which was a key 
design consideration). I disagree that PQ is a good model for motion 
picture production, though I am obviously biased. The reason I do not 
think that PQ, at least in 10 bit form, is good for movie production is 
related to its limitation for drama production. That is that PQ is, in a 
sense, fragile, in that banding may become visible if it is post 
produced. Of course this can be avoided if you use a 12 bit PQ format. 
But then there is probably a better format than PQ if you have 12 bits 
available. Personally I would be highly averse to having my expensively 
produced movie content mastered with 10 bit PQ when that might make my 
life difficult (risk of banding appearing) if I wanted to remaster 
(Director’s cut?).

Tim

On 18/06/2018 10:51, Craig Revie wrote:
>
> Hi Tim,
>
> Thanks for this detailed response which I hope will be helpful in the 
> PQ/HLG discussion. From the perspective of someone only peripherally 
> involved in the motion picture or broadcast television industry, it 
> seems that HLG provides a good solution for live broadcasts whereas PQ 
> provides a better model for motion picture production. Is that a 
> reasonable assumption? How do you expect that HDR BBC and NHK dramas 
> will be produced?
>
> I also see a statement on the World Cup 2018 link: “The production 
> workflow for the World Cup is not native HLG as Host Broadcaster 
> Services have defined their own HDR workflow.” Can you provide more 
> details about this?
>
> @Lars, given Tim’s description, it would seem that a ‘scene-referred’ 
> profile would make more sense than a display referred profile if the 
> intent is to allow archival of images encoded as HLG.
>
> Best regards,
>
> _Craig
>
> *From:*Tim Borer <tim.borer@bbc.co.uk>
> *Sent:* 18 June 2018 10:17
> *To:* Lars Borg <borg@adobe.com>; Craig Revie 
> <Craig.Revie@FFEI.co.uk>; Phil Green <green@colourspace.demon.co.uk>
> *Cc:* Leonard Rosenthol <lrosenth@adobe.com>; Max Derhak 
> <Max.Derhak@onyxgfx.com>; Simon Thompson-NM 
> <Simon.Thompson2@bbc.co.uk>; public-colorweb@w3.org
> *Subject:* Re: Help with HLG profile
>
> P.S. For more information see:
> World Cup 2018 in UHD HDR on BBC iPlayer 
> (https://www.bbc.co.uk/rd/blog/2018-05-uhd_hdr_world_cup_2018).
> The Royal Wedding in High Dynamic Range 
> (https://www.bbc.co.uk/rd/blog/2018-05-ultra-high-definition-dynamic-range-royal-wedding-uhd-hdr)
> Tim
>
> On 18/06/2018 09:46, Tim Borer wrote:
>
>     There are one or two inaccuracies in the thread. So I though it
>     worthwhile to introduce a few facts to correct these. Hope this is
>     useful.
>
>     It IS reasonable to describe HLG as relative scene luminance.
>     There has been a lot of debate by proponents of PQ (which is
>     absolute/non-relative display referred encoding) that this is not
>     really so. Nevertheless we designed HLG precisely as relative
>     scene luminance (just like Rec.709).
>
>     I have often heard it said that there is no standard Rec.709
>     production (because camera operators, it is claimed, universally
>     adjust their cameras). The claim is that by tweaking the camera
>     the picture somehow becomes display referred. Even if it were true
>     that cameras are always adjusted (not so) this would not make the
>     signal display referred. If you doubt this simply look at the
>     dimensions of the signal. HLG is dimensionless (a relative signal)
>     and PQ has dimensions of candelas per square metre (nits). All
>     that adjusting a 709/HLG camera does is to produce an “artistic”
>     modification to the signal. The signal still represents relative
>     scene referred light, just not the actual scene (but, rather, one
>     that the producer wished had existed). Adjusting the camera does
>     not convert a dimensionless signal into a dimensional one.
>
>     In fact a great deal of live television is produced using a
>     standard Rec709 OETF. This includes almost all live sport
>     (especially soccer), live light entertainment, and news. This
>     encompasses a large part of broadcast television output. In sport
>     it is often a contractual obligation to use the Rec 709 OETF. In
>     other instances the producers often do not like knees because, as
>     typically implemented, then can distort flesh tones. A further
>     consideration it that in a multicamera shoot it is essential to
>     match all the cameras. This is difficult if they don’t use a
>     standard Rec 709 setting (often cameras may have different
>     firmware versions, which means that setting up a camera does not
>     necessarily mean the same thing  even on the same model of
>     camera). It is not the case that “the camera’s linearity response
>     is tweaked by the operator for various reasons”. This is not
>     really viable in a multicamera live shoot, and the shaders don’t
>     have time to do it live. Similarly for live production the gamut
>     is standard Rec 709 (if necessary clipped from the wider camera
>     taking gamut). This is necessary to ensure consistent colours for
>     sporting strips both between cameras and at different venues and
>     different games. It is not unusual for sporting strips to be
>     outside 709, and it is important that such colours are treated in
>     a consistent way, so gamut mapping, other than simple clipping, is
>     not viable (bear in mind that footage from different games may
>     often be shown as part of the commentary). So, to emphasise, the
>     fact is that a great deal of television IS produced using the
>     standard Rec 709 OETF using standard 709 gamut (without gamut
>     mapping).
>
>     Scene referred conversions need to be used appropriately. When
>     used appropriately they do not create significant colour shifts.
>     Scene referred conversion should be used when matching camera
>     outputs (as opposed to matching the picture that is seen on the
>     display – they are not the same). Display referred conversions are
>     used to ensure that the displayed image is the same. There are
>     different, distinct, use cases for these two types of conversion.
>     It is a mistake to assume that all conversions should be display
>     referred. As an example consider the recent coverage of the Royal
>     Wedding. This was shot using a mixture of HLG HDR cameras and HD
>     cameras (using Rec 709). The production architecture was that
>     shown in ITU-R Report BT.2408-1 2018 (note the -1 version) (freely
>     available at https://www.itu.int/pub/R-REP-BT.2408-1-2018), figure
>     4, page 14. In this workflow you will note that there are many
>     scene referred Rec 709 to HLG conversions. This is so that
>     pictures can be shaded using standard Rec 709 monitors (which is a
>     requirement when the majority of viewers are watching in 709).
>     Note, in particular, that the final Rec 709 SDR output is
>     converted from the HLG signal using a scene referred conversion.
>     We estimate that the Royal Wedding was viewed by 1.8 billion
>     viewers. The international feed was derived from the HLG signal as
>     described, using a scene referred conversion. The colour was NOT
>     distorted using this conversion (and, clearly, the producers would
>     not have allowed distortion for such a prestigious broadcast). On
>     the other hand if one were producing primarily for an HDR audience
>     then you would use the alternative architecture in BT.2408 (fig 3,
>     page 12). Here shading is performed primarily on the HDR monitor
>     (with an SDR monitor fed by a DISPLAY referred conversion, so that
>     the shader can check that nothing untoward is happening on the SDR
>     signal). Note that in a joint HDR SDR production you can give
>     primacy to either shading in HDR (for a majority HDR audience) or
>     to shading in SDR (for a mainly SDR audience – the current
>     situation). But you cannot prioritise both. We have found that
>     shading in SDR gives very good quality HDR as well as SDR. NHK
>     have in mind producing for a primarily HDR audience and,
>     therefore, they favour the production workflow of figure 3. To
>     summarise scene referred conversion do not produce significant
>     colour shifts when they are used properly. Indeed without using
>     scene referred conversions it is not possible to match the look of
>     HDR and SDR output when shading in SDR.
>
>     There are few HDR broadcasts in Europe yet though a number are in
>     the pipeline. To the best of my knowledge all these broadcasts
>     will be using HLG. Similarly broadcasters that produce live
>     content (such as sport) in the US also favour HLG. The BBC has
>     made our Planet Earth II series available in UHD HDR HLG on catch
>     up (OTT) television, and are showing some of the Soccer World Cup
>     matches is HLG HDR OTT. Most OTT movie distribution currently uses
>     PQ (HDR10). This is possible because of the non-live workflow. I
>     am unaware of live sporting events broadcast using PQ. YouTube
>     distribute in both HLG and HDR10. Since production is easier in
>     HLG (particularly with pro-summer equipment) most of the user
>     generated HDR content on YouTube is HLG.
>
>     Best regards,
>     Tim
>
>     Dr Tim Borer MA, MSc, PhD, CEng, MIET, SMIEEE, Fellow SMPTE
>
>     Lead Engineer
>
>     Immersive & Interactive Content
>
>     BBC Research & Development
>
>     BBC Centre House, 56 Wood Lane, London  W12 7SB
>
>     T:  +44 (0)30304 09611  M: +44 (0)7745 108652
>
>     On 12/06/2018 05:20, Lars Borg wrote:
>
>         Hello Craig,
>
>         See below.
>
>         On 6/9/18, 9:12 PM, "Craig Revie" <Craig.Revie@FFEI.co.uk
>         <mailto:Craig.Revie@FFEI.co.uk>> wrote:
>
>             Hi Lars,
>
>             Thanks for your reply.
>
>             First of all on terminology, is it reasonable to describe
>             HLG as encoding relative scene luminance?
>
>         Not really. I wouldn’t.
>
>         It’s an approximation of scene colorimetry just like 709 or 2020.
>
>         How accurate is it in real production?
>
>         And what accuracy do you need? Why?
>
>         I haven’t seen any published tests.
>
>         But here’s what we know from 709 production.
>
>         I’ve yet to find anyone that sets their camera in reference
>         709 mode in real production.
>
>         Typically 709 productions do not use the standard OETF found
>         in the 709 spec.
>
>         The camera’s linearity response is tweaked by the operator for
>         various reasons.
>
>         Extra suppression of the darks as a means to reduce noise.
>
>         And the typical knee for highlight rolloff. (Which HLG now
>         includes in a standard way)
>
>         Maybe there are options for gamut mapping (which is non-linear)
>
>         We usually do’t call these tweaks color grading, but rather
>         camera setup.
>
>         Either tweak changes the contrast relations from true scene
>         colorimetry.
>
>         These tweaks are not indicated in metadata (as HLG has no
>         such, and other formats seem to be proprietary or incomplete),
>         so you have no knowledge on how to undo them in post.
>
>             I am not very familiar with the technical details of the
>             cameras used for broadcast television but my assumption
>             was that the controls allow white balance, aperture
>             control and selection of filters. I also assume that the
>             sensor is linear
>
>         So far I agree with you.
>
>             and that there is minimal processing of the signal. If so,
>             the assumption of relative scene luminance (as described
>             in a number of papers) would seem to be at least a
>             reasonable approximation. Are these assumptions incorrect?
>
>         I doubt it. As I noted above, there are many in-camera
>         processing options. So the signal might be non-linear.
>
>             I think that for the uses outlined by Simon on this
>             thread, it would be helpful to have a V4 ICC profile even
>             if there are some limitations (which there may well be).
>             Is this something you could provide? It seems to me that
>             the more useful of the two profiles would be the ‘HLG
>             scene profile’ although depending on the result of our
>             discussion about terminology this may need a different
>             description.
>
>         I have yet to find a use case for an HLG scene profile.
>
>         Please explain how you would use it, and what workflow.
>
>         Primarily I see post production uses for an HLG reference
>         display profile.
>
>         With this profile I can mix display-referred content across
>         HLG, PQ, 709 media.
>
>         For example, the colors in a commercial are display-referred
>         and the repurposing to another media should preserve those
>         colors.  Scene-referred conversions wouldn’t cut it, so I
>         would not use an HLG scene profile for this.
>
>             On the point about ‘grading’, in talking to people from
>             the BBC and NHK, I understand that the main reason to
>             develop HLG was that for many use cases there is no
>             opportunity for grading, for example for live broadcasts.
>
>         Grading, no.
>
>         But camera matching, yes, also for live broadcasts.
>
>         It is the rare event where all cameras are of the same make,
>         model, and revision, including lens and lights.
>
>         In practice, cameras at major sports events include both HDR
>         and 709 cameras, different sensors, multiple brands, different
>         light setups, different codecs.
>
>         Same sports jersey => very different colors.
>
>         So some effort is often spent to make cameras produce similar
>         colors on output.
>
>         Same sports jersey => similar colors.
>
>         Most likely that matching process undermines true scene
>         colorimetry.
>
>         BT.2087 shows conversions from 709 to 2020.
>
>         My study shows that doing this ‘scene’-referred (case 2)
>         creates significant color shifts.
>
>             In practice, I would have thought that PQ would be used
>             for grading of film production and would be converted to
>             HLG at the time of broadcast.
>
>         Are there movie HLG broadcasts in Europe yet?
>
>         PQ for movie grading, yes.
>
>         Although Adobe Premiere is agnostic and lets you grade
>         (display-referred) HLG content as well.
>
>         But it seems movie distribution is mostly PQ (HDR10), not HLG.
>         Think Netflix, etc.
>
>         I like this diagram from Yoeri Geutskens
>         <https://www.linkedin.com/in/yoerigeutskens/>
>
>         More names in the PQ circle than in the HLG circle.
>
>         Lars
>
>             Best regards,
>
>             _Craig
>
>             ________________________________
>
>             From: Lars Borg <borg@adobe.com <mailto:borg@adobe.com>>
>
>             Sent: 10 June 2018 04:53:58
>
>             To: Craig Revie; Phil Green
>
>             Cc: Leonard Rosenthol; Max Derhak; Simon Thompson-NM;
>             public-colorweb@w3.org <mailto:public-colorweb@w3.org>
>
>             Subject: Re: Help with HLG profile
>
>             Hi Craig,
>
>             A very sensible question.
>
>             Rec. 2100 gives you two reference decodings for HLG media:
>             scene referred and  display referred @ 1000 nits.
>
>             Scene versus display is not a metadata item, but rather a
>             choice by the reader.
>
>             Presumably the camera operator optimized the camera
>             rendering for a pleasing appearance on the reference
>             display, so ‘scene’ is a misnomer, as it’s always been
>             also with Rec. 709.
>
>             At the consumer end, each HDR TV set (PQ or HLG) is
>             expected to apply some form of re-rendering based on its
>             assumed luminance (assumed as it is not actually measured
>             or calibrated). That would be your metadata source.
>             However, we should not expect that they implement anything
>             like what’s indicated in Rec. 2100. Power limits, motion
>             enhancements, user preferences, etc. are out of scope for
>             Rec.2100. This makes it rather meaningless to try to model
>             anything other than the reference display.
>
>             In a separate expert forum, a majority stated that even
>             the best consumer HDR TV sets are so bad, they should
>             never be used of color grading.
>
>             So this begs the question, who would need a parameterized
>             HLG decoder?
>
>             BTW, the HLG scene profile is trivially implementable in
>             V4. The reference display profile is a little bit more
>             complex in V4, but doable.
>
>             Thanks,
>
>             Lars Borg  |  Principal Scientist  |  Adobe  |  p.
>             408.536.2723  |  c. 408.391.9479  | borg@adobe.com
>             <mailto:borg@adobe.com>
>
>             On 6/8/18, 9:46 PM, "Craig Revie" <Craig.Revie@FFEI.co.uk
>             <mailto:Craig.Revie@FFEI.co.uk><mailto:Craig.Revie@FFEI.co.uk>
>             <mailto:Craig.Revie@FFEI.co.uk%3E>> wrote:
>
>             Hi Max and Phil,
>
>             I hesitate to ask as this may show my ignorance but I had
>             thought that HLG encodes relative scene luminance and does
>             not carry any metadata. In my understanding the choice of
>             the reference white is made by the camera/cameraman
>             shooting the scene and the camera signal is encoded as HLG
>             which makes this model ideal for broadcast television.
>
>             You seem to anticipate having max and min luminance values
>             - where do these come from?
>
>             What does the profile represent and how do you anticipate
>             it being used?
>
>             As I say, this may just show my ignorance...
>
>             _Craig
>
>             On 8 Jun 2018, at 23:18, Phil Green
>             <green@colourspace.demon.co.uk
>             <mailto:green@colourspace.demon.co.uk><mailto:green@colourspace.demon.co.uk>
>             <mailto:green@colourspace.demon.co.uk%3E>> wrote:
>
>             In my understanding yes, but you would not be able to pass
>             in the max and min luminance so would need a different
>             profile for each condition supported.
>
>             Phil
>
>             On 08/06/2018 16:28, Leonard Rosenthol wrote:
>
>             Can this profile be defined WITHOUT the calculator?
>
>             Leonard
>
>             From: Max Derhak <Max.Derhak@onyxgfx.com
>             <mailto:Max.Derhak@onyxgfx.com>><mailto:Max.Derhak@onyxgfx.com>
>
>             Date: Wednesday, June 6, 2018 at 2:43 PM
>
>             To: Simon Thompson-NM <Simon.Thompson2@bbc.co.uk
>             <mailto:Simon.Thompson2@bbc.co.uk>><mailto:Simon.Thompson2@bbc.co.uk>,
>             "public-colorweb@w3.org
>             <mailto:public-colorweb@w3.org>"<mailto:public-colorweb@w3.org>
>             <public-colorweb@w3.org
>             <mailto:public-colorweb@w3.org>><mailto:public-colorweb@w3.org>
>
>             Subject: RE: Help with HLG profile
>
>             Resent-From: <public-colorweb@w3.org
>             <mailto:public-colorweb@w3.org>><mailto:public-colorweb@w3.org>
>
>             Resent-Date: Wednesday, June 6, 2018 at 2:43 PM
>
>             Simon has indeed helped me, and I’m very grateful for his
>             assistance.  As it turns out there was a small bug in my
>             matlab/octave code.
>
>             Based on my matlab/octave code I have been able to create
>             iccMAX profiles for both narrow range and full range
>             encoding of Rec 2100 using Hgl curves. I created XML
>             representations of the profiles and used the iccFromXML
>             tool from the reference implementation to create the
>             profiles for testing using the iccMAX reference
>             implementation CMM.
>
>             Significant features of these prototype profiles include:
>
>               *   Full floating point based algorithmic encoding of
>             RGB to XYZ and XYZ to RGB tags using calculator processing
>             elements
>
>               *   Uses a D65 based PCS
>
>               *   Max and min luminances can be passed in as CMM
>             environment variables to adjust Hlg curves
>
>               *   The profiles use display relative Y=100 for max
>             white for default relative intent processing
>
>               *   Scene relative luminances can be supported with CMM
>             luminance matching using the spectral viewing conditions
>             tag (part of Profile Connection Conditions – PCC)
>             illuminant white point luminance.  (Note: Using CMM
>             control options for luminance based matching by CMM allows
>             for scene relative luminances to be used and adjusted
>             for.  The PCC can be externally substituted to define an
>             alternate white point luminance for luminance scaling, but
>             matching values for CMM environment variables are also
>             needed to ensure that the corresponding Hlg curves are used).
>
>             An Interoperability Conformance Specification (ICS) is
>             needed to help define specific profile and CMM
>             requirements for this type of profile.  That is something
>             that the ICC display working group will work on.
>
>             None of this can be directly accomplished using a single
>             V4 profile.  V4 uses display relative with a D50 PCS (with
>             chromatic adaptation applied).  By playing around with
>             defining the media white point one can achieve a level of
>             luminance scaling using absolute intent with some possible
>             interoperability issues to contend with.  The Hlg
>             algorithm cannot be directly encoded in v4, and LUTs and
>             inverse LUTs using interpolation need to be populated for
>             a fixed scene luminance condition with different profiles
>             created for different scene luminances.
>
>             Regards,
>
>             Max Derhak (PhD)
>
>             Principal Scientist
>
>             From: Simon Thompson-NM [mailto:Simon.Thompson2@bbc.co.uk]
>
>             Sent: Tuesday, May 29, 2018 8:52 AM
>
>             To: public-colorweb@w3.org
>             <mailto:public-colorweb@w3.org><mailto:public-colorweb@w3.org>
>
>             Subject: Re: Help with HLG profile
>
>             Hi Chris, all,
>
>             I’ve already sent a code correction to Max, so hopefully
>             that will fix the issue he was seeing.
>
>             I’ll comment further inline, below.
>
>             From: Chris Lilley [mailto:chris@w3.org]
>
>             On 17-May-18 23:25, Max Derhak wrote:
>
>             Hi,
>
>             I have an action item in the ICC Display Working group to
>             develop an HLG based iccMAX display profile.  In order to
>             understand how to go about it I’ve first prototyped
>             functionality in Matlab/Octave.
>
>             The attached zip file has my code along with the BT2100
>             document that I’m using to implement..  The problem is
>             that for a display profile you need to have both device to
>             PCS as well as PCS to device transforms.
>
>             The device to PCS transform is conceptually implemented in
>             HLG_FullToXYZ.m, and the PCS to device is conceptually
>             implemented in HLG_XYZToFull.m  (I’m using full 0.0 to 1.0
>             range encoding in this case).  Alternatively one could use
>             the HLG_Narrow12ToXYZ.m and HLG_XYZToNarrow12.m to use the
>             narrow 12-bit integer encoding.
>
>             The problem is that the OOTF (implemented in
>             HLG_EOTF.m)  and inverse OOTF (implemented in HLG_invEOTF)
>             functions are not logical inverses of each other (from
>             what I can tell from the docs).
>
>             I recall hearing that these are not round-trippable.
>
>             The equations for HLG are reversible and we have used the
>             reverse transforms for converting other HDR formats to
>             HLG, converting SDR camera feeds to HLG and converting HLG
>             to SDR.  An example use case is given in:
>             https://na01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.bbc.co.uk%2Frd%2Fblog%2F2018-05-ultra-high-definition-dynamic-range-royal-wedding-uhd-hdr&data=02%7C01%7Cborg%40adobe.com%7Cc687232c3775491b340f08d5cea18e1c%7Cfa7b1b5a7b34438794aed2c178decee1%7C0%7C0%7C636642115681164772&sdata=eICRO%2Fa3ISG%2Fxm50j3UznDG5HMD1Ekf5YHc6uCxp5%2F4%3D&reserved=0<https://na01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.bbc.co.uk%2Frd%2Fblog%2F2018-05-ultra-high-definition-dynamic-range-royal-wedding-uhd-hdr&data=02%7C01%7Clrosenth%40adobe.com%7Cb810dc2b06c24735603308d5cbdd749e%7Cfa7b1b5a7b34438794aed2c178decee1%7C0%7C1%7C636639074360711277&sdata=R%2BFSqmXWBTIxF8EfODM8ZR83S4jkiC8YwMpWTlFzi4Q%3D&reserved=0>
>             <https://na01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.bbc.co.uk%2Frd%2Fblog%2F2018-05-ultra-high-definition-dynamic-range-royal-wedding-uhd-hdr&data=02%7C01%7Cborg%40adobe.com%7Cc687232c3775491b340f08d5cea18e1c%7Cfa7b1b5a7b34438794aed2c178decee1%7C0%7C0%7C636642115681164772&sdata=eICRO%2Fa3ISG%2Fxm50j3UznDG5HMD1Ekf5YHc6uCxp5%2F4%3D&reserved=0%3Chttps://na01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.bbc.co.uk%2Frd%2Fblog%2F2018-05-ultra-high-definition-dynamic-range-royal-wedding-uhd-hdr&data=02%7C01%7Clrosenth%40adobe.com%7Cb810dc2b06c24735603308d5cbdd749e%7Cfa7b1b5a7b34438794aed2c178decee1%7C0%7C1%7C636639074360711277&sdata=R%2BFSqmXWBTIxF8EfODM8ZR83S4jkiC8YwMpWTlFzi4Q%3D&reserved=0%3E>
>
>             On the other hand the BBC claim that the transcode looks
>             "identical"
>
>             A more complete description of the process of transcoding
>             between HDR formats is given in ITU-R BT.2390 section 7:
>             https://na01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.itu.int%2Fdms_pub%2Fitu-r%2Fopb%2Frep%2FR-REP-BT.2390-4-2018-PDF-E.pdf&data=02%7C01%7Cborg%40adobe.com%7Cc687232c3775491b340f08d5cea18e1c%7Cfa7b1b5a7b34438794aed2c178decee1%7C0%7C1%7C636642115681164772&sdata=ZLkH19GPIpEJ3v48wDdMaoIkMDT8aGfgOleSjeXPVoI%3D&reserved=0<https://na01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.itu.int%2Fdms_pub%2Fitu-r%2Fopb%2Frep%2FR-REP-BT.2390-4-2018-PDF-E.pdf&data=02%7C01%7Clrosenth%40adobe.com%7Cb810dc2b06c24735603308d5cbdd749e%7Cfa7b1b5a7b34438794aed2c178decee1%7C0%7C1%7C636639074360711277&sdata=cXEstDUoMa2r2vIP1fmlx57urfV5uyxbR2hOEjEFbQc%3D&reserved=0>
>             <https://na01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.itu.int%2Fdms_pub%2Fitu-r%2Fopb%2Frep%2FR-REP-BT.2390-4-2018-PDF-E.pdf&data=02%7C01%7Cborg%40adobe.com%7Cc687232c3775491b340f08d5cea18e1c%7Cfa7b1b5a7b34438794aed2c178decee1%7C0%7C1%7C636642115681164772&sdata=ZLkH19GPIpEJ3v48wDdMaoIkMDT8aGfgOleSjeXPVoI%3D&reserved=0%3Chttps://na01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.itu.int%2Fdms_pub%2Fitu-r%2Fopb%2Frep%2FR-REP-BT.2390-4-2018-PDF-E.pdf&data=02%7C01%7Clrosenth%40adobe.com%7Cb810dc2b06c24735603308d5cbdd749e%7Cfa7b1b5a7b34438794aed2c178decee1%7C0%7C1%7C636639074360711277&sdata=cXEstDUoMa2r2vIP1fmlx57urfV5uyxbR2hOEjEFbQc%3D&reserved=0%3E>
>
>             *Also it would be incredibly helpful to better understand
>             what is the purpose of having an HLG ICC profile?
>
>             There are a few general use cases that we’ve thought of so
>             far which apply equally to all HDR variants:
>
>             ·       Storage of subtitles and other still images –
>             currently still formats like PNG can only store a gamma
>             value in the header files – the only way to store
>             non-gamma encoded images is to embed an ICC
>             Profile.  Currently for PQ HDR, there’s a draft proposal
>             that looks for a given ICC Profile filename in the header
>             which then over-rides both the header and profile.  We
>             would prefer to have the correct ICC profiles available.
>
>             ·       Allowing operating systems to correctly display
>             images on non-gamma displays.
>
>             ·       IP disptribution platforms (both PC based and
>             Set-top box will need to display video and background
>             images) – e.g. a video embedded in a webpage, you may have
>             a video box in HDR and a surrounding webpage in sRGB, both
>             of which need to be correctly displayed and need an ICC
>             profile description.
>
>             Any transforms from SDR to HDR will need to place the SDR
>             diffuse white at the correct signal level (given in ITU-R
>             BT.2408) – I’m not sure how this is encoded in to the
>             transforms.
>
>             Best Regards
>
>             Simon
>
>             --
>
>             Simon Thompson MEng CEng MIET
>
>             Project R&D Engineer
>
>             BBC Research and Development South Laboratory
>
>             ________________________________
>
>             [FFEI
>             Limited]<https://na01.safelinks.protection.outlook.com/?url=http%3A%2F%2Fwww.ffei.co.uk&data=02%7C01%7Cborg%40adobe.com%7C95e992930a4b4a0f85c308d5cddd420a%7Cfa7b1b5a7b34438794aed2c178decee1%7C0%7C1%7C636641272535313819&sdata=Q1alNsLsCwIaIzgnNuFnw45OG31IyZE1TqVlXo8XBCM%3D&reserved=0>
>
>             CONFIDENTIALITY AND DISCLAIMER NOTICE
>
>             This message and any attachment is confidential and is
>             protected by copyright. If you are not the intended
>             recipient, please email the sender and delete this message
>             and any attachment from your system.
>
>             Dissemination and or copying of this email is prohibited
>             if you are not the intended recipient. We believe, but do
>             not warrant, that this email and any attachments are virus
>             free. You should take full responsibility for virus checking.
>
>             No responsibility is accepted by FFEI Ltd for personal
>             emails or emails unconnected with FFEI Limited's business.
>
>             FFEI Limited is a limited company registered in England
>             and Wales (Registered Number: 3244452).
>
>             [Join us on Linked
>             In]<https://na01.safelinks.protection.outlook.com/?url=http%3A%2F%2Fwww.linkedin.com%2Fcompany%2Fffei&data=02%7C01%7Cborg%40adobe.com%7C95e992930a4b4a0f85c308d5cddd420a%7Cfa7b1b5a7b34438794aed2c178decee1%7C0%7C0%7C636641272535313819&sdata=e4Mg0RADSEh5xmatm7jdcxGZ9Og0E9bnIj%2BAA5HK2kM%3D&reserved=0>[Follow
>             <https://na01.safelinks.protection.outlook.com/?url=http%3A%2F%2Fwww.linkedin.com%2Fcompany%2Fffei&data=02%7C01%7Cborg%40adobe.com%7C95e992930a4b4a0f85c308d5cddd420a%7Cfa7b1b5a7b34438794aed2c178decee1%7C0%7C0%7C636641272535313819&sdata=e4Mg0RADSEh5xmatm7jdcxGZ9Og0E9bnIj%2BAA5HK2kM%3D&reserved=0%3E%5bFollow>
>             @FFEI_ltd]<https://na01.safelinks.protection.outlook.com/?url=https%3A%2F%2Ftwitter.com%2FFFEI_ltd&data=02%7C01%7Cborg%40adobe.com%7C95e992930a4b4a0f85c308d5cddd420a%7Cfa7b1b5a7b34438794aed2c178decee1%7C0%7C0%7C636641272535313819&sdata=WAHld0A%2BGPGtnugMfF52J1cfJignDk0J4%2FFrsHGZ%2F34%3D&reserved=0>[FFEI
>             <https://na01.safelinks.protection.outlook.com/?url=https%3A%2F%2Ftwitter.com%2FFFEI_ltd&data=02%7C01%7Cborg%40adobe.com%7C95e992930a4b4a0f85c308d5cddd420a%7Cfa7b1b5a7b34438794aed2c178decee1%7C0%7C0%7C636641272535313819&sdata=WAHld0A%2BGPGtnugMfF52J1cfJignDk0J4%2FFrsHGZ%2F34%3D&reserved=0%3E%5bFFEI>
>             YouTube
>             Channel]<https://na01.safelinks.protection.outlook.com/?url=http%3A%2F%2Fwww.youtube.com%2Fuser%2FFFEIPrintTechnology&data=02%7C01%7Cborg%40adobe.com%7C95e992930a4b4a0f85c308d5cddd420a%7Cfa7b1b5a7b34438794aed2c178decee1%7C0%7C0%7C636641272535313819&sdata=5G6oBnD43AAKg976Cs1M1%2FlXFf0Urol%2BjaQoIDY3CTI%3D&reserved=0>
>
>             Registered Office: The Cube, Maylands Avenue, Hemel
>             Hempstead, Hertfordshire, HP2 7DF, England.
>