An easy way to replace the artwork location in the gamelist.xml with another / new one is the sed command (stream editor). This example changes the video directory from the relative path ./media/videos/ to the absolute path /mnt/artwork/videos/:
cp gamelist.xml gamelist.xml.backup # make a backup in case something goes wrong
sed -i 's#<video>./media/#<video>/mnt/artwork/#g' gamelist.xml
The part in single quotes does the actual sed-magic:
s(earch)#[old string]#[new string]#g(lobally, i.e. all occurences)
This works for every other path, just change <video> to <image>, <marquee> etc. Omitting the artwork tag before the path will change any occurence in the file, e.g. if the whole artwork is located in another place.
Execute man sed in the command line to get the manpage (manual page) of this tool, or search the web for myriads of examples.
@shavecat You could use my script to resize all videos automatically. You'd just have to teach yourself the necessary ffmpeg options to change the resolution instead of (or in addition to) the colour encoding and add them to the ffmpeg line in my script.
@bfollowell What video player option are you using in Emulationstation ? omxplayer, the HW accelerated option, has issues with some videos. If you switch off the hw accelerated video, do the videos play ok ?
I really didn't setup a player. I just put the media files in the individual ROMs folders, along with my gamelist.xml file, and the videos showed up and started playing. So, whatever player RetroPie uses by default, and however it is setup.
Actually, before I submitted this, I decided to go and check. I found OMX Player (HW Accelerated) listed under the Main Menu under Other Settings. This was off. I turned it on, and the videos for TG16 start much faster now. There is still a slight delay, but only about a second. I still have no idea why it's only this one system that exhibits this behavior, but I'm happy with it now.