Does Dolby Vision get converted to HDR on non-DV television?

[Vacendak]

Hi, I have an LG 49UM7300PUA and it supports only HDR (4K Active HDR (HDR10, HLG), HDR Dynamic Tone Mapping). Does content that is Dolby Vision get converted to HDR by Jellyfin if I played it through a supported app on Apple TV? Or do I have to start with HDR content. Thanks.

"It's complicated", especially, because i've overlooked the "on AppleTV" part . So the following is more general:

Currently, Jellyfin can only do tonemapping into SDR, and you need a GPU to actually do that. ffmpeg can tonemap into SDR and HDR, so this is likely something that jellyfin will support at some time in the future, just not right now.

But, depending on your DV Source, this isn't at all relevant to you! There isn't just "the DolbyVision", it has multiple profiles with vastly different capabilities (If you want to know more), the worst being profile 5, used by streaming-services, which uses a proprietary color-encoding, this you *have* to transcode to watch it on a non-DV-Hardware (otherwise it looks horribly green/purple tinted).

The other profiles (mainly 7.x and 8.x) are basically normal HDR10/HDR10+ videostreams, with *additional* DV-information that's just ignored by a device that cant handle them. Those streams should play in HDR.

Now, back to your AppleTV, i'm not sure about the models, but at least the latest model does support (only!) DolbyVision Profile 5, and i *assume*, it can tonemap this down to HDR10

TL; DR: You will have to try it yourself. Best case scenario, everything plays in HDR, because Profile 5 is tonemapped in hardware by the Apple TV, and Profile 8 contains HDR!