一、转码并截图的命令分析：
1、转码并截图，将码率转换为900K
ffmpeg -i E:\1.MOV -i E:\123.jpg -filter_complex overlay=W-w -b:v 900k E:\UPUPW_AP5.3vhostswww.wnbm110.comyizhuan1.mp4
2、转码并截图，将视频宽高转换为320*240
ffmpeg -i E:\1.MOV -i E:\123.jpg -filter_complex overlay=W-w -s 320x240 E:\UPUPW_AP5.3vhostswww.wnbm110.comyizhuan2.mp4
3、转码并截图，原样转码
ffmpeg -i E:\1.MOV -i E:\123.jpg -filter_complex overlay=W-w E:\UPUPW_AP5.3vhostswww.wnbm110.comyizhuan4.mp4