error while merging videos with ffmpeg

Question

I am trying to concat videos with different resolutions using ffmpeg and I am encountering this error shown below while that the video resizes when playing the videos

I merge them using ffmpeg with

ffmpeg -f concat -i mylist.txt -c copy output.webm

and the mylist.txt has

file '1.webm' duration 00:00:03.71
file '2.webm' duration 00:00:00.21
file '3.webm' duration 00:00:00.21
file '4.webm' duration 00:00:00.46

the files 2 and 3 have a different frame size than 1 and 4 and I would like to merge them without scaling and re-encoding to concat. I assume the player dynamically resizes the frmae and I also checked out the resize the QT option in VLC

Can anyone please help me figure out how to concat them?

P.S I realize the videos are from movie Amazing Spiderman. I am not pirating the movie, this is from a clip only.