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2025-04-20, 02:00 AM
On my machine with hardware acceleration and a decent CPU, burning in subtitles results in a fraction of the fps I get with normal transcoding. I am seeing numbers like 600 -> 80fps for a 1080p stream. Is this typical?
System: Ryzen 2600x Arc a380 32GB ram Jellyfin 10.10.7 Docker on Ubuntu
2025-04-20, 04:20 AM
(This post was last modified: 2025-04-20, 04:25 AM by Efficient_Good_5784. Edited 2 times in total.)
Burning in subtitles requires the CPU to do the computational work of placing the subs on the video. ASS subs will also require more computational work to figure out the exact positions to place subs as stated in their scripts if they contain any position tags.
That's completely normal. Only way to improve the speed of a transcode when it comes to burning in subs with Jellyfin would be to get a more modern/faster CPU, or drop the resolution so that there's less pixels that has to be processed. From my understanding, what's basically happening each video frame is: 1. The GPU decodes the video frame 2. The CPU retrieves the decoded video frame 3. The CPU computes where subs go over the video frame and places subs there 4. The CPU hands the finished frame back to the GPU 5. The GPU encodes the frame to the final format for the intended client I may be wrong with the exact process, but that's the general gist of what happens. |
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