format of output video

[Programming lover]

Thanks for such a great work.
I have a question (may be off-topic), I'm trying to save the output video in mp4 format but I'm getting error
[mov,mp4,m4a,3gp,3g2,mj2 @ 0x56294b5339a0]
moov atom not found pipe:: Invalid data found when processing input

mov format is working but mp4 is not working. Kindly suggest some solution.