synology docker Jellyfin very slow and high iowait when FFmpeg Transcode

[allen]

Hi, there! I deployed Jellyfin using Docker on my Synology NAS and enabled hardware acceleration. However, when I start playing a video, my Synology becomes extremely slow and the system experiences very severe iowait. Can anyone help me look into this? Here are some system info and logs.

Synology:

• Model name DS224+
  
• CPU INTEL Celeron J4125
  
• CPU Clock rate 2 GHz
  
• Total physical memory 2048 MB
  

FFmpeg log:


/usr/lib/jellyfin-ffmpeg/ffmpeg -analyzeduration 200M -probesize 1G -f matroska -init_hw_device vaapi=va:/dev/dri/renderD128,driver=iHD -init_hw_device qsv=qs@va -filter_hw_device qs -canvas_size 1920x1080 -i file:"/video2/xxxx.UHD.BluRay.2160p.HDR.TrueHD.Atmos7.1.5.Audio.x265.10bit-DreamHD/xxx.UHD.BluRay.2160p.HDR.TrueHD.Atmos7.1.5.Audio.x265.10bit-DreamHD.mkv" -map_metadata -1 -map_chapters -1 -threads 0 -map 0:0 -map 0:1 -map -0:0 -codec:v:0 h264_qsv -preset veryfast -mbbrc 1 -b:v 33385810 -maxrate 33385811 -rc_init_occupancy 66771620 -bufsize 133543240 -profile:v:0 high -level 51 -g:v:0 72 -keyint_min:v:0 72 -filter_complex "[0:6]scale,scale=3840:2160:fast_bilinear[sub];[0:0]setparams=color_primaries=bt709:color_trc=bt709:colorspace=bt709,scale=trunc(min(max(iw\,ih*a)\,min(3840\,2160*a))/2)*2:trunc(min(max(iw/a\,ih)\,min(3840/a\,2160))/2)*2,format=yuv420p[main];[main][sub]overlay=eof_action=pass:repeatlast=0" -start_at_zero -codec:a:0 libfdk_aac -ac 2 -ab 256000 -af "volume=2" -copyts -avoid_negative_ts disabled -max_muxing_queue_size 2048 -f hls -max_delay 5000000 -hls_time 3 -hls_segment_type fmp4 -hls_fmp4_init_filename "f156cdfa9cdbd2c25287b9473e82ad8a-1.mp4" -start_number 0 -hls_segment_filename "/cache/transcodes/f156cdfa9cdbd2c25287b9473e82ad8a%d.mp4" -hls_playlist_type vod -hls_list_size 0 -hls_segment_options movflags=+frag_discont -y "/cache/transcodes/f156cdfa9cdbd2c25287b9473e82ad8a.m3u8"

ffmpeg version 7.1.2-Jellyfin Copyright © 2000-2025 the FFmpeg developers
  built with gcc 14 (Debian 14.2.0-19)
  configuration: --prefix=/usr/lib/jellyfin-ffmpeg --target-os=linux --extra-version=Jellyfin --disable-doc --disable-ffplay --disable-static --disable-libxcb --disable-sdl2 --disable-xlib --enable-lto=auto --enable-gpl --enable-version3 --enable-shared --enable-gmp --enable-gnutls --enable-chromaprint --enable-opencl --enable-libdrm --enable-libxml2 --enable-libass --enable-libfreetype --enable-libfribidi --enable-libfontconfig --enable-libharfbuzz --enable-libbluray --enable-libmp3lame --enable-libopus --enable-libtheora --enable-libvorbis --enable-libopenmpt --enable-libdav1d --enable-libsvtav1 --enable-libwebp --enable-libvpx --enable-libx264 --enable-libx265 --enable-libzvbi --enable-libzimg --enable-libfdk-aac --arch=amd64 --enable-libshaderc --enable-libplacebo --enable-vulkan --enable-vaapi --enable-amf --enable-libvpl --enable-ffnvcodec --enable-cuda --enable-cuda-llvm --enable-cuvid --enable-nvdec --enable-nvenc
  libavutil      59. 39.100 / 59. 39.100
  libavcodec    61. 19.101 / 61. 19.101
  libavformat    61.  7.100 / 61.  7.100
  libavdevice    61.  3.100 / 61.  3.100
  libavfilter    10.  4.100 / 10.  4.100
  libswscale      8.  3.100 /  8.  3.100
  libswresample  5.  3.100 /  5.  3.100
  libpostproc    58.  3.100 / 58.  3.100
libva info: VA-API version 1.22.0
libva info: Trying to open /usr/lib/jellyfin-ffmpeg/lib/dri/iHD_drv_video.so
libva info: Found init function __vaDriverInit_1_22
libva info: va_openDriver() returns 0


Metadata:
    encoder        : libebml v1.3.6 + libmatroska v1.4.9
    creation_time  : 2019-11-05T07:54:17.000000Z
  Duration: 01:34:40.72, start: 0.000000, bitrate: 33385 kb/s
  Chapters:

[hls @ 0x7fa2606c7580] Opening '/cache/transcodes/bd57a9652f27716f4f6f9ae4acc42b87-1.mp4' for writing
Output #0, hls, to '/cache/transcodes/bd57a9652f27716f4f6f9ae4acc42b87.m3u8':
  Metadata:
    encoder        : Lavf61.7.100
  Stream #0:0: Video: h264, nv12(tv, bt709, progressive), 3840x2160 [SAR 1:1 DAR 16:9], q=2-31, 33385 kb/s, 23.97 fps, 26201 tbn
      Metadata:
        encoder        : Lavc61.19.101 h264_qsv
      Side data:
        Mastering Display Metadata, has_primaries:1 has_luminance:1 r(0.6800,0.3200) g(0.2650,0.6900) b(0.1500 0.0600) wp(0.3127, 0.3290) min_luminance=0.000000, max_luminance=1000.000000
        Content Light Level Metadata, MaxCLL=0, MaxFALL=0
        cpb: bitrate max/min/avg: 33385811/0/33385810 buffer size: 133543240 vbv_delay: N/A
  Stream #0:1: Audio: aac, 48000 Hz, stereo, s16, 256 kb/s (default)
      Metadata:
        encoder        : Lavc61.19.101 libfdk_aac
      Side data:
        cpb: bitrate max/min/avg: 256000/256000/256000 buffer size: 0 vbv_delay: N/A
frame=    0 fps=0.0 q=0.0 size=N/A time=N/A bitrate=N/A speed=N/A   
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Jellyfin & Docker Configuration：

version: '3.8'
services:
  jellyfin:
    image: jellyfin/jellyfin:2025112405
    container_name: jellyfin
    restart: unless-stopped
    ports:
      - "8096:8096"
    volumes:
        - /volume1/video:/video
        - /volume1/docker/jellyfin/cache:/cache
        - /volume1/docker/jellyfin/config:/config
        - /volume1/downloads/complete:/video2
    environment:
      - UID=0
      - GID=0
      - GIDLIST=0
    devices:
      - /dev/dri/renderD128:/dev/dri/renderD128
      - /dev/dri/card0:/dev/dri/card0
    user:937