After trying various video players to establish the best performer, I've found VLC to be the most all round efficient and capable and on my G5, H264 files up to and including 1080p are fine. However, on my 1.25 Powerbook, 720p H264 are a no-no (less intensive codecs are fine), so after some web trawling I've found a solution using mplayer. I've used MPlayerOSX before and whilst effective, it's less capable than VLC - on my machines anyway. But I knew using the mplayer binary from Terminal was efficient albeit a little unwieldy in ease of use. So what I've done is wrapped some mplayer Terminal commands together into an Apple Script, compiled it as an app and designed an icon to make it look presentable To use it you need the mplayer binary in your Applications folder and then simply drop a movie file onto the icon wherever you've placed it - you can use an alias or put it in the dock too. The script opens the movie full screen and from there on all normal mplayer keyboard shortcuts control playback. Apart from being more efficient because there's no slick GUI to accommodate, there're commands in the script to cache the file and skip/drop frames which make unplayable 720p H264s now workable. To get the mplayer binary I extracted it from this version of MPlayerOSX: http://www.mplayerhq.hu/MPlayer/releases/MPlayerOSX_1.0rc1.dmg I tried a few versions but this is the one that worked. To extract mplayer, mount the dmg, right click the ppc pkg to show package contents, open Contents folder, copy and paste Archive.pax.gz to another location, double click to extract it. Right click the MPlayer app to show package contents, open Contents folder, open Resources folder, open External_Binaries folder, right click to show package contents of mplayer_ppc, open Contents folder, open MacOS folder and inside is the mplayer binary which you copy and paste to the Applications folder. I've only tested this on my Powerbook under Tiger, so can't guarantee an improvement on every Mac, though I'd imagine all single processor G4s should benefit.