Personally, I'd give norgo's SMPlayer builds a look. I've never had the slightest issue with playing anything in these. (May need to install mPlayer from the repos, if it's not already installed.)
I would, however, endorse what's been previously stated on this thread. Check ffmpeg! Puppies often come with older/stripped-back variants of this, so it's worth seeing if you can update it.... John van Sickle's static builds are highly recommended. (You may need to search the "old releases" to find a date-sympathetic version for the age of your Pup, however; despite being 'statically-compiled', the newest versions can still sometimes complain about stuff missing that's needed.)
It's solved several issues for me over the years. Curiously, Bionicpup64 has thrown up a LOT of issues for me; things that worked fine in earlier Pups have refused point-blank to play ball with this one.....and have then inexplicably started working again in later Puppies. Weird.
Mike. 