After a lot of research and testing, I wrote a command that I can adapt for multiple sources to be concatenated using FFMPEG. I'm running into a problem though with add looped images (as videos) into the concatenation.
Here's the command:
ffmpeg -y -i input1.mp4 -c copy -bsf:v h264_mp4toannexb -f mpegts temp1 2> /dev/null & \ ffmpeg -y -i input2.mp4 -c copy -bsf:v h264_mp4toannexb -f mpegts temp2 2> /dev/null & \ ffmpeg -y -f lavfi -i anullsrc -loop 1 -f image2 -i input3.jpg -r 30 -t 3 -pix_fmt yuvj420p -map 0:a -map 1:v -f mpegts temp3 2> /dev/null & \ ffmpeg -y -f mpegts -i "concat:temp1|temp2|temp3" -bsf:a aac_adtstoasc out.mp4
The end result should be 2 videos, then an image looped for 3 seconds (with no audio), all concatenated into a long video. Instead, all I get is a single concatenated video that contains the first two videos, but not the image looped.