buffering when skipping through movies

[kallom93]

I'm fairly new to the NAS/Homelab/Server thing - but I think I managed to get the Jellyfin(10.9.11) docker container on Ubuntu 24.04 running with gpu passthrough and hardware acceleration enabled.
It is working correctly, I think (I can see in the logs when things get transcoded)

A problem I have is that when I'm skipping through a movie, there is a lot of buffering happening before the playback continues which I don't have when I'm playing the same file from the smb share with vlc player.
I checked my cpu(i3-7100), or ram(8gb) usage but it looks fine to me.
Most of my media are blu ray remuxes and according to jellyfin logs only the 5.1 dts audio has to be transcoded. But I even checked with stereo sound only, so it's direct play and the buffering times don't improve.

Since it's not buffering when directly played over network with VLC, I guess it's not network or HDD reading speed issues.

I noticed it because often times the "continue" feature didn`t keep the right time, so I had to manually search and had to deal with 3-5 seconds buffering on every step until I found the right scene.
It's worse on the IOS apps, than in the browser, but still compared to direct play from the smb share it's not a very good performance.

Any ideas what I can do? It would be a huge QoL improvement.

[TheDreadPirate]

Are you certain it is direct playing? It sounds like it is transcoding. If it is transcoding, and you skipped ahead of the point in the video that has already been transcoded, it will take a second for Jellyfin restart ffmpeg at that point and build up a buffer of transcode files to serve.

But direct play in Jellyfin, in my experience, is almost identical as playing a local file in VLC/MPV/<insert other player>.

Can you share your logs via pastebin? We'd be able to figure out how it is playing the videos with the logs.

[kallom93]

This is playback with web browser(Firefox) directstream
https://pastebin.com/6Cx4nthU

And this is from IOS App playback with transcoding
https://pastebin.com/UmuaQUTD

never used pastebin before, don't know if that's right.

[TheDreadPirate]

"Direct stream" = audio transcoding, video is copied unmodified
"Transcode" = video transcoding, audio may or may not also be transcoding
"Remux" = video and audio are copied, unmodified, into a new container
"Direct play" = file sent directly to the client in its original form

My statement about skipping past the point that has already been transcoded is the likely cause. And this is expected. If you skip to a point in the video that HAS already been transcoded, it should be near instantaneous.

[kallom93]

What's the best way to reduce that time to fully transcode a movie/episode and skip through the file with almost no buffering?
Of course, I can make sure that the playback device supports most of my codecs, but on server side is there anything that can be done?

[TheDreadPirate]

Getting a dedicated GPU is probably the most cost effective way to speed up transcoding. Ensure that the OS runs on a SSD.

Regardless of how fast your server is, if you skip ahead of where it has transcoded there will be some amount of delay vs direct play. The way ffmpeg works, it cannot simply skip ahead to where you selected. ffmpeg has to be stopped and another ffmpeg process started at the new position.