1. Flip video vertically:
ffmpeg -i INPUT -vf vflip -c:a copy OUTPUT
2. Flip video horizontally:
ffmpeg -i INPUT -vf hflip -c:a copy OUTPUT
3. Rotate 90 degrees clockwise:
ffmpeg -i INPUT -vf transpose=1 -c:a copy OUTPUT
4. Rotate 90 degrees counterclockwise:
ffmpeg -i INPUT -vf transpose=2 -c:a copy OUTPUT
CORETECH 
Thank you! I’ve trawled the forums and the question gets answered in a dogs’ breakfast sort of way. However your answer is beautiful, simple and exact. Thank you.
So simple, but so helpful. Thanks for publishing this!