http://m.zhizuobiao.com/node/node-19061200018/
ffmpeg -list_devices true -f dshow -i dummy
ffmpeg -f dshow -i video="screen-capture-recorder" -f dshow -i audio="virtual-audio-capturer" -pix_fmt yuv420p -vcodec libx264 -g 19 -s 1280x720 -r 15 -q 10 -ar 44100 -ac 2 -tune zerolatency -preset ultrafast -f flv "rtmp://localhost:1935/live/"
pause