Some rough notes on merging videos side by side with ffmpeg 2

ffmpeg \
-i "v1.mp4" \
-i "v2.mp4" \
-filter_complex " \
nullsrc=size=1900x950 [base]; \
[0:v] setpts=PTS-STARTPTS, scale=950x950 [left]; \
[1:v] setpts=PTS-STARTPTS, scale=950x950 [right]; \
[base][left] overlay=shortest=1 [tmp1]; \
[tmp1][right] overlay=shortest=1:x=950 \
" \
-c:v libx264 output2.mkv

ffmpeg \
-i "v1.mp4" \
-i "v2.mp4" \
-i "v3.mp4" \
-i "v4.mp4" \
-filter_complex " \
nullsrc=size=1900x1900 [base]; \
[0:v] setpts=PTS-STARTPTS, scale=950x950 [upperleft]; \
[1:v] setpts=PTS-STARTPTS, scale=950x950 [upperright]; \
[2:v] setpts=PTS-STARTPTS, scale=950x950 [lowerleft]; \
[3:v] setpts=PTS-STARTPTS, scale=950x950 [lowerright]; \
[base][upperleft] overlay=shortest=1 [tmp1]; \
[tmp1][upperright] overlay=shortest=1:x=950 [tmp2]; \
[tmp2][lowerleft] overlay=shortest=1:y=950 [tmp3]; \
[tmp3][lowerright] overlay=shortest=1:x=950:y=950 \
" \
-c:v libx264 output4.mkv

ffmpeg \
-i "video.mp4" \
-i "drones/0/video.mp4" \
-i "drones/1/video.mp4" \
-i "drones/2/video.mp4" \
-i "drones/3/video.mp4" \
-i "drones/4/video.mp4" \
-filter_complex " \
nullsrc=size=2850x1900 [base]; \
[0:v] setpts=PTS-STARTPTS, scale=950x950 [upperleft]; \
[1:v] setpts=PTS-STARTPTS, scale=950x950 [uppermiddle]; \
[2:v] setpts=PTS-STARTPTS, scale=950x950 [upperleft]; \
[3:v] setpts=PTS-STARTPTS, scale=950x950 [lowerleft]; \
[4:v] setpts=PTS-STARTPTS, scale=950x950 [lowermiddle]; \
[5:v] setpts=PTS-STARTPTS, scale=950x950 [lowerright]; \
[base][upperleft] overlay=shortest=1 [tmp1]; \
[tmp1][uppermiddle] overlay=shortest=1:x=950 [tmp2]; \
[tmp2][upperleft] overlay=shortest=1:x=1900 [tmp3]; \
[tmp3][lowerleft] overlay=shortest=1:y=950 [tmp4]; \
[tmp4][lowermiddle] overlay=shortest=1:y=950:x=950 [tmp5]; \
[tmp5][lowerright] overlay=shortest=1:y=950:x=1900 \
" \
-c:v libx264 output6.mkv