trim
ffmpeg -i input.mp4 -ss 00:01:00 -to 00:02:00 -c copy output.mp4
merage
ffmpeg -f concat -i input.txt -c copy output.mp4
input.txt
file '1.flv'
file '2.flv'
flv2mp4
ffmpeg -i input.flv -c copy output.mp4
rename
ls *.mp4 | sed 's/\(.*\).flv\(.*\).*/mv & \1\2/' | sh
