ffmpeg -rtsp_transport tcp -i "rtsp://admin:Pass@192.168.88.76:554/h264" -rtsp_transport tcp -i "rtsp://admin:Pass@192.168.88.76:554/h264" -filter_complex " nullsrc=size=200x100 [background];[0:v] setpts=PTS-STARTPTS, scale=100x100 [left]; [1:v] setpts=PTS-STARTPTS, scale=100x100 [right]; [background][left]       overlay=shortest=1       [background+left];[background+left][right] overlay=shortest=1:x=100 [left+right]" -c:v libx264 output.mkv