Originally Posted by bodosom
The ATV4K doesn't currently support HLG (but it's worth remembering that Apple's "pro" tools support all common HDR formats). In practice this means the provider should do the conversion not that you should get an audio only presentation. HLG is intended to be intrinsically compatible with SDR (it's a broadcast format after all for both television types) so "discarding" the HDR sprinkles should leave SDR. For extra points the app+CDN could do an HLG to HDR-10 conversion. Either one of these approaches results in ATV4K compatible video.
Originally Posted by GregCh
Exactly. So it seems that if they were really getting HLG over a streaming app then it should work fine as as standard SDR. From what I understand the SDR content from HLG is even upscaled and better quality than regular transmission SDR.
I haven't played with the Fox Sports Apps yet but it would surprise me if an ATV app from a vendor was streaming content that was unplayable on the ATV. That just makes no sense. Why have a streaming app for the ATV that streams content in a format that is incompatible with the ATV?
To be honest, I'm not sure technically that an HLG stream would be able to be "stripped" to show SDR. I am far from an expert in broadcast tech but HLG HDR info is in parts of the gamma curve unused in "Old tech" SDR broadcasts, so it is simply not seen by SDR equipment. It's exploiting the limitations of TVs and old transmission equipment. It has no metadata. Once digitised and streamed I'd be surprised if this trickery applies. I'd expect any box, like the ATV, would need to be HLG compatible, or at least aware, to accurately display even the SDR image, although I'd admit to not being positive about this.
On the other hand, I totally agree that it would be mad to send such a stream to a non-HLG box. There should be no reason why they could not simply send an SDR stream instead.
On the other, other hand, they may choose not to. Apart from the very first UHD trial, when an SDR version was made available on some devices, the BBC have ONLY supplied UHD with HLG and non-HLG compatible devices have been limited HD. Also, Sky appear to have decided to only provide one UHD stream to their STBs (a different situation I accept). All need to support that stream to play it. So, with some content providers, non HLG compatible systems could be limited to HD in future.