====== fix mp4 video to whatsapp ======

<code>
ffmpeg -i FILES.mp4 \
-c:v libx264 -profile:v baseline -crf 28 -level 3.0 -pix_fmt yuv420p -ac 2 -vf scale="iw/2:ih/2" \
-vcodec libx265 -crf 28 \
 FLIEO.mp4


ffmpeg -i FILES.mp4 \
-c:v libx265  -crf 28 -level 3.0 -pix_fmt yuv420p -ac 2 -vf scale="iw/2:ih/2" \
 FLIEO.mp4


</code>

===== Concat videos to single =====

<code>
for f in *.mp4; do echo "file '$f'" >> list.txt; done
ffmpeg -safe 0 -f concat -i list.txt -c copy output.mp4
</code>