it's more complicated than i thought
from https://trac.ffmpeg.org/wiki/Concatenate
ffmpeg -i input1.mp4 -c copy -bsf:v h264_mp4toannexb -f mpegts intermediate1.ts ffmpeg -i input2.mp4 -c copy -bsf:v h264_mp4toannexb -f mpegts intermediate2.ts ffmpeg -i "concat:intermediate1.ts|intermediate2.ts" -c copy -bsf:a aac_adtstoasc output.mp4 these three commands work for me but "ffmpeg -f concat -safe 0 -i list.txt -c copy ready.mp4" doesn't work i have used bing.com to search answer, but it doesn't show https://trac.ffmpeg.org/wiki/Concatenate on 1st page