How can I mirror flip a video horizontally under Mac OS X?
I found an answer to the question in How can I mirror image a video easily? but VLC cannot export video so you would have to re-record it – not professional.
The option within VLC is called transcoding
If it's a Quicktime supported format you can also use Quicktime X to flip and save the video
I'm with you all the way to "VLC cannot export video". Tina's answer in 2010 still holds.
You can flip the image (Tools=>Effects and Filters, /Video Effects, /Geometry, tick "Transform" and choose "Flip Horizontaly" then click [Close]). You then choose Convert/Save... and VLC will save the file. VLC will transcode the file digitally, same as any video effects program. This is not "rerecording it" in the sense that it converts it to an anaglogue signal and redigitises it, but a completely digital reencoding of the file, and the results will be as good as they can be. Any change to a compressed format will lead to some loss of quality, but VLC will not reduce the quality any more than is absolutely necessary.