推流修改比特率和帧数：
streamlink $URL 720p -O | ffmpeg -re -i pipe:0 -vcodec h264 -b:v 300k -r 15 -c:a aac -f flv $RTMP
https://blog.csdn.net/DaveBobo/article/details/80685328
https://ffmpeg.org/documentation.html
https://www.cnblogs.com/chen1987lei/archive/2010/12/03/1895242.html