remix

conflicting requests
  - nothing provides libSDL2-2.0.so.0()(64bit) needed by ffmpeg-4.2.4-1.el8.x86_64
  - nothing provides libSDL2-2.0.so.0()(64bit) needed by libavdevice-4.2.4-1.el8.x86_64

$ sudo dnf install https://download1.rpmfusion.org/free/el/rpmfusion-free-release-8.noarch.rpm

$ sudo dnf install https://download1.rpmfusion.org/nonfree/el/rpmfusion-nonfree-release-8.noarch.rpm

$ sudo dnf install http://rpmfind.net/linux/epel/7/x86_64/Packages/s/SDL2-2.0.14-2.el7.x86_64.rpm

　このバージョンが僅かに上がっている為
http://rpmfind.net/linux/epel/7/x86_64/Packages/s/
から最新のものを指定することでパス。

$ sudo dnf install ffmpeg ffmpeg-devel

$ ffmpeg -version
ffmpeg version 4.2.4 Copyright (c) 2000-2020 the FFmpeg developers

　ffmpeg で webm を mp4 に変換。

$ ffmpeg -i movie.webm movie.mp4
	Too many packets buffered for output stream 0:0.577014:32:22.77 bitrate=  -0.0kbits/s dup=54 drop=0 speed=N/A

　↓

$ ffmpeg -i movie.webm -max_muxing_queue_size 99999 movie.mp4