Transcoding issue in v10.8.12

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Code:

/usr/lib/jellyfin-ffmpeg/ffmpeg -analyzeduration 200M -probesize 1G -f matroska -init_hw_device vaapi=va:/dev/dri/renderD128,driver=iHD -hwaccel vaapi -hwaccel_output_format vaapi -noautorotate -i file:"/media/films/TEST/TEST.mkv"

Yes, it's using VA-API hardware acceleration. I would agree with you that this is unacceptable. What is the processor in your NAS? Most of the time they're underpowered and although you may be able to use VA-API, it's not cutting it. If new enough, you may be able to upgrade to QSV for better results, but it seems a bit off that your performance is so piss poor.