ffmpeg -f v4l2 -i /dev/video0 -video_size 1280x720 -framerate 30 -vcodec mjpeg -i /dev/video1 -video_size 1280x720 -framerate 30 -vcodec mjpeg  -filter_complex "[0:v]pad=2560:720,setpts=PTS-STARTPTS[bg]; [1:v]setpts=PTS-STARTPTS[fg]; [bg][fg]overlay=720[out]" -map [out] -threads 0 outputsplit.ts