2. # 截取视频画面一部分范围 widhth:high:position_x:position_y
    3. ffmpeg -i 0523PM.mp4 -y -filter:v "crop=987:719:155:246" -nostdin -y -movflags +faststart 0523PM_crop.mp4
    4. -f image2 -ss 1 -vframes 1 cap2.
    6. # cut video from 00:03:40 with length 00:36:24
    7. ffmpeg -ss 00:03:40 -t 00:36:24 -i 0523PM_crop.mp4 -vcodec copy -acodec copy jianyi_b.mp4
    9. # conversion video to audio from 00:41:40
    10. ffmpeg -ss 00:41:40 -t 00:34:10 -i 0523PM_crop.mp4 -vn -ar 44100 -ac 2 -ab 192k -f mp3 2shuji.mp3
    12. # capture video at 01:18:00 with 1 frame
    13. ffmpeg -i 0523PM.mp4 -ss 01:18:00 -y -f image2 -ss 1 -vframes 1 cap.jpeg
    16. ffmpeg -ss 01:15:54 -t 02:34:10 -i 0523PM.mp4 -filter:v "crop=275:155:1305:247" -nostdin -y -movflags +faststart -acodec copy 3lianxi.mp4