FFmpeg is needed to trasform your uploaded video file to formats used by ootb video component. When you uploading video in the DAM CQ there is called automatically a workflow "DAM Update Asset" which in the step "FFmpeg transcoding" creates three new rendition for you video file (flv,ogg and m4v). If you check a logs there you find that ther is called ffmpeg with parameters set for standard video profiles defined in the CQ. You can check them by navigating following path: /etc/dam/video
Could you please tell me the reason why we are installing ffmpeg for video player?
-- I guess you are not installing FFMPEG for video player but for transcoding video formate, So that videos can be played in different browser (FFMPEG converts your vedio to browser compatible formate). More information