默認使用udp推流：
ffmpeg -i "rtsp://admin:cmable8888@192.168.70.6:554/cam/realmonitor?channel=1&subtype=0" -f flv -r 25 -s 1920*1080 -an "rtmp://192.168.91.107/oflaDemo/cm192_168_70_6"
使用tcp推流：
ffmpeg -rtsp_transport tcp -i "rtsp://admin:cmable8888@192.168.70.6:554/cam/realmonitor?channel=1&subtype=0" -f flv -r 25 -s 1920*1080 -an "rtmp://192.168.91.107/oflaDemo/cm192_168_70_6"