Vertical video play does not sync with multiple stacked video

Question

I dont know if I have wrote the subject well and if that can be understood. Nevertheless, here is an explanation

I have 7 videos of different dimensions where the width is same (1080). I wish to place them one below the other to get a full hd vertical video (1080x1920). I tried the -filter_complex vstack filter in ffmpeg and got all the videos aligned one below the other and I am getting a perfect 1080x1920 full hd vertical video but they dont sync with each other. Once the videos are in sync, I need to put an audio too which should also sync with the in-sync video that will be made.

There is so much of complexity. Please advice how do I make them sync. Is there any software that can allow me to put 7 videos one below the other in a timeline? (if not 7, atleast 3-4 videos). Please advice where and how to start.

Is there any option in Adobe Premier or any other software?

Thanks

EDIT: I am doing a very long procedure to combine all 7 videos vertically

first i use

ffmpeg -i video1.mp4 -i video2.mp4 -preset veryslow -filter_complex vstack video12.mp4

and then

ffmpeg -i video12.mp4 -i video3.mp4 -preset veryslow -filter_complex vstack video123.mp4

so on and so forth

Is there a better way to do it all in one command?

Answer 1

For your question regarding the ffmpeg stacking command, yes—there is a way to do this in a single command. vstack can be used to combine more than two videos if you specify the number:

    ffmpeg -i video1.mp4 -i video2.mp4 -i video3.mp4 -i video4.mp4 -i video5.mp4 -i video6.mp4 -i video7.mp4 -i audio.mp3 \
    -filter_complex [0:v][1:v][2:v][3:v][4:v][5:v][6:v]vstack=7[v]; -map "[v]" -map 8:a output.mp4