Sky Glass is Not a Good Television (Not my words)

[LGUser]

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@SimonW wrote:

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The strangest thing is knowing they were going to start HDR broadcasts and were going to use HLG (as for broadcast its really the only choice otherwise they have to send out two different streams, one SDR and one HDR. HLG lets them include both in a single stream) you would have thought they would have wanted the TV to really sell it yet which it stands no chance of doing with its setup

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I don't actually see the need for HLG because Sky is not using HLG properly. They are treating HLG like it was HDR10. Programs in UHD/HDR have two UHD versions. One is UHD/HDR and the other is UHD/SDR. Sky is not putting up the HLG version as the UHD version. They are putting up both versions. Have a look at the UHD list of films from Sky Cinema and you will see that all the films that are UHD/HDR also have a UHD/SDR version. Take a look at the program Cobra. Season 2 is available to download in UHD/HDR and UHD/SDR. Also, there is another issue. If your Q box is set to HD, you do not get shown the UHD/HDR versions of content but you do get shown the UHD/SDR version.

So why is it that Sky is not treating HLG properly and just giving us one version to download making it much easier to watch the HDR version? Isn't one of the features of HLG is that if the TV doesn't support HLG, we get the picture as SDR?

Sky would have been better off with HDR10 for non-live content and HLG for live content.

[SimonW]

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@LGUser wrote:

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@SimonW wrote:

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The strangest thing is knowing they were going to start HDR broadcasts and were going to use HLG (as for broadcast its really the only choice otherwise they have to send out two different streams, one SDR and one HDR. HLG lets them include both in a single stream) you would have thought they would have wanted the TV to really sell it yet which it stands no chance of doing with its setup

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I don't actually see the need for HLG because Sky is not using HLG properly. They are treating HLG like it was HDR10. Programs in UHD/HDR have two UHD versions. One is UHD/HDR and the other is UHD/SDR. Sky is not putting up the HLG version as the UHD version. They are putting up both versions. Have a look at the UHD list of films from Sky Cinema and you will see that all the films that are UHD/HDR also have a UHD/SDR version. Take a look at the program Cobra. Season 2 is available to download in UHD/HDR and UHD/SDR. Also, there is another issue. If your Q box is set to HD, you do not get shown the UHD/HDR versions of content but you do get shown the UHD/SDR version.

So why is it that Sky is not treating HLG properly and just giving us one version to download making it much easier to watch the HDR version? Isn't one of the features of HLG is that if the TV doesn't support HLG, we get the picture as SDR?

Sky would have been better off with HDR10 for non-live content and HLG for live content.

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On the downloads they may be splitting them but they aren't on the broadcasts though and most likely it's much easier for them to only need to use one process for HDR

[LGUser]

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@SimonW wrote:

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On the downloads they may be splitting them but they aren't on the broadcasts though and most likely it's much easier for them to only need to use one process for HDR

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I would prefer (and I think others) HDR10 for downloads and to split the UHD live programs. Most 4k TVs in use support HDR10. More so then TVs that support HLG.

[tarbat]

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@LGUser wrote:
Isn't one of the features of HLG is that if the TV doesn't support HLG, we get the picture as SDR?

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In theory, yes, in practice no. A TV that can only display SDR may very well also only accept BT.709 colour space. So that SDR TV, when receiving an HLG BT.2100 image will exhibit two problems:

1. Dark picture, since reference white for HLG is 75% whereas reference white for SDR is around 90-95%
2. Colour shifts, if the TV can't handle the BT.2100 colour space.

[bob1234]

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@tarbat wrote:

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@LGUser wrote:
Isn't one of the features of HLG is that if the TV doesn't support HLG, we get the picture as SDR?

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In theory, yes, in practice no. A TV that can only display SDR may very well also only accept BT.709 colour space. So that SDR TV, when receiving an HLG BT.2100 image will exhibit two problems:

1. Dark picture, since reference white for HLG is 75% whereas reference white for SDR is around 90-95%
2. Colour shifts, if the TV can't handle the BT.2100 colour space.

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That was a problem that the early Amazon fire sticks had, you saw all sorts of strange colours with SDR sets until they updated the software.

[LGUser]

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@tarbat wrote:

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@LGUser wrote:
Isn't one of the features of HLG is that if the TV doesn't support HLG, we get the picture as SDR?

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In theory, yes, in practice no. A TV that can only display SDR may very well also only accept BT.709 colour space. So that SDR TV, when receiving an HLG BT.2100 image will exhibit two problems:

1. Dark picture, since reference white for HLG is 75% whereas reference white for SDR is around 90-95%
2. Colour shifts, if the TV can't handle the BT.2100 colour space.

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Does a program with HLG modify the BT709 color space? I thought that HLG was an add-on to the signal to allow HLG and if you cannot display HLG, that add-on is ignored and youget the BT709 picture as you should. If I am incorrect, what happens when watching a program with HLG on a TV that has HDR but not HLG and a TV that does not have HDR?

[tarbat]

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@LGUser wrote:
Does a program with HLG modify the BT709 color space? I thought that HLG was an add-on to the signal to allow HLG and if you cannot display HLG, that add-on is ignored and youget the BT709 picture as you should.

HLG content complies with BT.2100, so uses the BT.2020 colour space. Typically constrained to the DCI-P3 colour space, but still BT.2020.

HLG is not an "add-on to the signal", it's completely different to BT.709 SDR. It's 10-bit, HDR(HLG) EOTF in a BT.2020 colour space. To get BT.709 colour space the Sky Glass TV (or Sky Q box) would have to transform BT.2020 to BT.709.

Explained in this video at 6:45 onwards:

[video]

[d2h]

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@LGUser wrote:

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@SimonW wrote:

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On the downloads they may be splitting them but they aren't on the broadcasts though and most likely it's much easier for them to only need to use one process for HDR

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I would prefer (and I think others) HDR10 for downloads and to split the UHD live programs. Most 4k TVs in use support HDR10. More so then TVs that support HLG.

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The vast majority of on-demand titles are HDR10. 

Sky have insisted from day one to ensure the viewer passes a HLG check first - presumably for consistency to ensure they can also view Sky Sports HDR, which is HLG. 

[LGUser]

Thanks @tarbat. The video is brilliant and really doesa good job of explaining HLG.

[LGUser]

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@d2h wrote:

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The vast majority of on-demand titles are HDR10. 

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They are HLG. I've not seen a single UHD/HDR from Sky Q be in HDR10. If I am incorrect, please lst some programs that are HDR10 so I can try them.

[d2h]

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@LGUser wrote:

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@d2h wrote:

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The vast majority of on-demand titles are HDR10. 

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They are HLG. I've not seen a single UHD/HDR from Sky Q be in HDR10. If I am incorrect, please lst some programs that are HDR10 so I can try them.

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No, they're HDR10. Sky then add the HLG wraparound before play out. 

The only native HLG content from Sky is live sport. 

[LGUser]

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@d2h wrote:

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@LGUser wrote:

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@d2h wrote:

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The vast majority of on-demand titles are HDR10. 

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They are HLG. I've not seen a single UHD/HDR from Sky Q be in HDR10. If I am incorrect, please lst some programs that are HDR10 so I can try them.

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No, they're HDR10. Sky then add the HLG wraparound before play out. 

The only native HLG content from Sky is live sport. 

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Where did you read this? I've never heard of HDR10 with an HLG wrapper. Sky have never mentioned HDR10.

[d2h]

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@LGUser wrote:

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@d2h wrote:

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@LGUser wrote:

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@d2h wrote:

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The vast majority of on-demand titles are HDR10. 

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They are HLG. I've not seen a single UHD/HDR from Sky Q be in HDR10. If I am incorrect, please lst some programs that are HDR10 so I can try them.

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No, they're HDR10. Sky then add the HLG wraparound before play out. 

The only native HLG content from Sky is live sport. 

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Where did you read this? I've never heard of HDR10 with an HLG wrapper. Sky have never mentioned HDR10.

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Sky's production guidelines stipulate all content - whether in-house production or third-party licensed - is delivered in PQ - HDR10. 

None of their on-demand content is native HLG. 

[LGUser]

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@d2h wrote:

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Sky's production guidelines stipulate all content - whether in-house production or third-party licensed - is delivered in PQ - HDR10. 

None of their on-demand content is native HLG. 

How can you have an HLG wrapper on HDR10? Is there anyplace to read about this? Also, is there anyplace to read about Sky's HDR10 production guidelines?

[tarbat]

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@d2h wrote:
Sky's production guidelines stipulate all content - whether in-house production or third-party licensed - is delivered in PQ - HDR10.

And despite their production guidelines saying that they'll conform HDR10(PQ) content to HLG at 1000cd/m2, they decide to manufacture a TV with peak luminance of around half that value. Crazy?

Maybe Sky should grade their HLG content on a Sky Glass TV to ensure optimum picture quality on Sky Glass 😉