I always use Handbrake for doing such things. It's fairly fast and easy enough to use.
give me a few minutes and I'll dig out the original posts someone made from launch month if I can find them.
EDIT: Here you go
Originally the details were posted up by TouchMyBox in the Vita Launch thread.
http://www.neogaf.com/forum/showpost.php?p=35176352&postcount=12334
Then I had a play with different quality settings
Most of the settings shown in those images are defaults, and you don't HAVE to change the resolution if you don't want to. Myself and TouchMyBox only did so as it made the files smaller. Since the Vita can now handle a 1080 video it just needs to be converted to MP4 but I imagine the file size will be large and hence take longer to transfer over and use up more expensive memory card space.
If you have a play and have any questions just ask
I have to say, South Park and Thrones both looked amazing even at just 100MB and 600MB respectively.
You mean on the Flickr app on the Vita or on the website?