Synology + HDR Content

[SendPiePlz]

I will preface that I am new to both Jellyfin and 4K Blu-ray HDR ripping.

I setup a Jellyfin server running in docker on my Synology DS1520+ NAS from the official repo following the Jellyfin guide on the website. I was able to upload a 4K HDR mkv rip of Dunkirk to my NAS and watch it on my 2021 12.9in iPad Pro (With the MiniLED screen) with the Swiftfin app without any playback issues. (No stuttering or tearing and scrubbing worked well)

However, I felt that the movie did not appear to actually be playing in HDR. Being on an iPad I have no real way to verify other than my eyes, but that got me looking into how HDR works on Jellyfin. (Also, not sure if Dunkirk is just a bad HDR movie).

From what I have read from Jellyfin's documentation I need basically any modern CPU or GPU that isn't ARM based to be able to transcode HDR on the Jellyfin server. The NAS has an ARM based CPU/GPU.

This is where my first question comes into play, if I uploaded HDR content to Jellyfin and play it on an HDR compatible device like an iPad does it do any transcoding? While watching on the iPad is nice, I plan to do most of my movie viewing on a Windows computer. This computer has an RTX 4080 and an OLED ultrawide from Dell so HDR should be fully supported. (I know it is when playing games).

But in either of these cases would the Jellyfin server actually be transcoding anything for the end devices or are the end devices handling the HDR? (I read something about offloading the HDR transcoding to the end device in the documentation but didn't fully understand it) 

Or is some form of HDR support on the device the Jellyfin server is running on necessary for HDR content to be viewed at all?

[TheDreadPirate]

This is where my first question comes into play, if I uploaded HDR content to Jellyfin and play it on an HDR compatible device like an iPad does it do any transcoding? While watching on the iPad is nice, I plan to do most of my movie viewing on a Windows computer. This computer has an RTX 4080 and an OLED ultrawide from Dell so HDR should be fully supported. (I know it is when playing games).

Your Jellyfin server will only transcode when the client tells it to.  It is possible that the client incorrectly determines it can't play something directly and asks for a transcode.  Or the other way around.  It can't play something and doesn't ask for a transcode when it should.

The actual HDR data is separate from the video.  So if your client mistakenly determines it can play HDR but actually can't it will still play but with washed out colors.  It is very obvious.  When I play HDR content on my not HDR Windows 10 PC monitor it is not transcoding or tone mapping and the video looks normal.   So you saying that you couldn't tell might indicate that your iPad is processing the video correctly?

[bitmap]

However, I felt that the movie did not appear to actually be playing in HDR. Being on an iPad I have no real way to verify other than my eyes, but that got me looking into how HDR works on Jellyfin. (Also, not sure if Dunkirk is just a bad HDR movie).

[...]

This is where my first question comes into play, if I uploaded HDR content to Jellyfin and play it on an HDR compatible device like an iPad does it do any transcoding? While watching on the iPad is nice, I plan to do most of my movie viewing on a Windows computer. This computer has an RTX 4080 and an OLED ultrawide from Dell so HDR should be fully supported. (I know it is when playing games).

But in either of these cases would the Jellyfin server actually be transcoding anything for the end devices or are the end devices handling the HDR? (I read something about offloading the HDR transcoding to the end device in the documentation but didn't fully understand it) 

Or is some form of HDR support on the device the Jellyfin server is running on necessary for HDR content to be viewed at all?

To add to what TDP said, most clients will have an option to view playback information. This should tell you if the media is a) being transcoded, b) the bitrate, and c) additional information such as codec, bit-depth, dynamic range, etc... Depending on your client (the app you're using for playback), how to access this will differ. If you care to share, somebody might be able to help you find that information.

Additionally, I just want to point out that only your server will ever transcode. You cannot offload transcoding to your client. If you're watching on a beastly PC and your server is an rPi, it won't make a difference. Your client requests the media when you click a thumbnail and tells the server, "Hey, this is the type of client that I am." The server looks up the corresponding client device profile, decides whether transcoding and/or tonemapping is required, executes neither one, or both based on the profile, and streams the result to the client. All transcoding and tonemapping happens server-side. If direct play is chosen, interpretation of HDR metadata (which is separate from the media, technically) is done by the client. But that's not transcoding.

The server itself does NOT need to support HDR at all in order to direct stream anything. If you are transcoding, whatever you are using to transcode (CPU-only or hardware acceleration device) must support the codec(s) being transcoded. Most of the time HDR doesn't come in to play, with a few exceptions generally only reserved for DolbyVision, which you won't see if you're limiting yourself to UHD BR rips.

[SendPiePlz]

Sorry for not responding sooner TDP and bitmap. Both of your explanations clarified and explained things. The reason I did not respond sooner was that I was working on ripping more UHD Blu Rays. This has led me down another rabbit hole and hopefully someone here can explain things to me.

I have switched to DVDfab for ripping my UHD blu rays from makemkv. During this I have encountered a couple of things.

DVDfab will sometimes select MP4 as the format over MKV when ripping. According to DVDFab's website MP4 is required for Dolby Vision to work. However, by default it removes the Dolby Vision information so I'm not sure why it selects that format.

Dolby Vision has to be supported on the end device to function. According to Apple the 2021 iPad Pro with the mini-LED screen does support Dolby Vision. I looked on Dell's website and could not find official support for Dolby Vision on the Alienware AW3423DWF monitor.

So, my questions are as follows:

1. Is it worth ripping to MP4 to save the Dolby Vision information?
1a. If I do rip to mp4 for Dolby Vision should I also rip an mkv copy with HDR10 for devices that don't support Dolby Vision?
2. Does the Jellyfin media player support Dolby Vision?
3. Would I be better off just creating ISOs of the blu rays?

[TheDreadPirate]

MP4 is required for DV profile 5 to work. The other two common profiles, 7 and 8, work in either MP4 or MKV containers. Dolby Vision profile 8.1 falls back to HDR10.

https://en.wikipedia.org/wiki/Dolby_Vision#Profiles

Jellyfin does support Dolby Vision and will tone map HDR to SDR during transcoding (if the server's GPU supports it).

If you rip to an MKV I think there are tools to recontainerize to MP4. ffmpeg comes to mind.

[SendPiePlz]

To clarify, if Dolby Vision is supported by the end device it will do a direct stream. If Dolby Vision is not supported, it would need to transcode the HDR to SDR signal, unless it is profile 8.1 in which case it would fall back to HDR10?

Could I also have an SDR and HDR version of a movie on the Jellyfin server? Or would that confuse the Jellyfin server? Since my Jellyfin server does not support transcoding?

[TheDreadPirate]

For MOVIES jellyfin supports multiple versions. So you could 100% do a pre-converted SDR version of an HDR movie and have both as selectable options under the same listing.

https://jellyfin.org/docs/general/server...of-a-movie

[SendPiePlz]

Thanks for the clarification! I appreciate all the help TDP!