Scrubbing Speed Extremely Slow?

[KevinCCucumber]

I've got Jellyfin running on TrueNAS Scale. The media pool is 4 HDDs in raid-z1 which is also set up as an SMB share. The media pool is mounted to the container, so my library isn't reading it via SMB. I've been using a 36GB mkv file to test with. Whenever I skip around on the timeline through the Jellyfin web interface, it takes a solid ~15 seconds for the video to buffer and start playing. Doing the same through VLC directly from the SMB share doesn't have this problem, video plays immediately. Using a smaller mkv file ~2GB doesn't have this problem.

I have no GPU installed, but if I always stream at native resolution then I shouldn't ever need to transcode, right?

My CPU is a 5900X (12 cores) and I've configured my CPU resource for the Jellyfin app to "24000m". It took me some playing around with this number to figure out that this value should allow Jellyfin to take up all 24 threads. It does use up all 24 threads, but only at about ~60% utilization per thread. Where can I find documentation on the meaning of the units for this variable? Does this come from TrueNAS or Jellyfin?

I've enabled Jellyfin to use 128GiB of memory for transcoding, but I've never seen it take up more than 10GiB of memory anyway. I have seen my ZFS Cache grow to 36GB though, so it's probably loaded the entire video into memory.

So what am I missing? Is it unreasonable to expect Jellyfin to perform as well as VLC in this scenario? I'd expect them to be the same since I'm reading the same data from the same drive and displaying it on the same computer.

[KevinCCucumber]

So immediately after posting this I found the "Playback Info" menu.



Looks like it's transcoding afterall. I guess it needs to transcode for reasons other than resolution. Guess I should install a GPU.

[Topomov]

What client are you using?

It says on your screenshot that the reason for the transcoding is that your client does not support your file codec. I suspect you're using your browser; you should probably look into using the Jellyfin media player: https://github.com/jellyfin/jellyfin-media-player that supports most (if not all?) codecs supported by Jellyfin natively.

Allowing you not to transcode your files.

[KevinCCucumber]

Yeah the native apps work great on my M1 Mac and WebOS. But I've also got a 1st gen iPad Pro I'm trying to use and Swiftfin is chugging.

I have a spare RX460 I decided to put into my server. Really scraping the bottom of the barrel, but it ought to be better than CPU transcoding, right? Problem is, I'm not convinced Jellyfin is even using it. I'm still getting the ~15 second buffer when skipping through the video on the web client.

I've allocated 1 GPU to Jellyfin through TrueNAS's app config.


I've enabled hardware transcoding through the Jellyfin Dashboard. Based on the documentation for AMD GPUs AMF with AV1 disabled should be the best config for an RX460.


But during playback, radeontop shows no utilization and all CPU cores are still being hit.



I will probably need a better GPU eventually anyway, but I'd at least like to confirm that Jellyfin can use my GPU at all before I go out buying something new.

[Venson]

Hey @KevinCCucumber

Could you please upload a logfile and a ffmpeg logfile from when you tried to playback that file to an external site like pastebin?

[KevinCCucumber]

Hitting play on the video already in progress, waiting for it to actually play, and then skipping to another point in the timeline and waiting for that to play, produced 5 ffmpeg logs. They're all available here: https://paste.ee/p/HBvgc

[Venson]

Hey @KevinCCucumber

According to your logfiles, you are not using hardware transcoding for some reason.


Stream mapping:
Stream #0:0 -> #0:0 (hevc (native) -> h264 (libx264))