ffmpeg -y -itsoffset 00:00:00.500 -i /storage/emulated/0/Camera/video.mp4 -i /storage/emulated/0/sunflower.mp3 -map 0:v -c:v copy -filter_complex [0:a][1:a]amix[aout] -map [aout] -shortest /storage/emulated/0/out.mp4

I was expecting the video/audio stream of the mp4 file to be delayed by half a second, however the output file looks the same as previously when i ran the command without the '-itsoffset'