It's possible qmplay2-devel benefits a lot from OpenGL acceleration - I have a build without that enabled for Mac OS Tiger that is considerably less performant (though still correct) when using streamlink to stream any xfiles episode from plutotv. At the 1000k bitrate, a 1.5 Ghz PowerBook G4 on reduced mode (figure 750 Mhz) can stream an episode at roughly 70% CPU usage with
@alex_free 's excellent ffplay (from PPCMC) with sound and video in sync, and, as far as I can tell, no frames dropped. The same PowerBook G4 needs full CPU power to play the same file with QMPlay2-devel, and still drops a few frames, though everything else is correct. Of course, that is on a build with no OpenGL acceleration, though with the +G4 variant and LTO.
My guess is that QMPlay2 is too heavy for the minimum Leopard/Snow Leopard configuration with a terrible graphics card like the Nvidia Geforce2 MX (which has no OpenGL 2 support) on an 867 Mhz PowerMac G4.
Your recommendation from your website that mplayer is preferred over QMPlay2 for resource constrained systems is likely correct. And in my experience,
@alex_free 's ffplay build is an excellent balance of correctness (a struggle for mplayer), modernity (can stream over https!), and cpu usage (reasonable).
And for downloaded video in the codecs it supports, I don't really see any open source video player competing with coreplayer in low CPU usage, but coreplayer is lacking in ability to stream video and fails to play some modern codecs at all.
My guess is that with OpenGL enabled, QMPlay2 is probably best for any Power PC Mac that has a good OpenGL 2.0 supporting graphics card better than Nvidia FX Go 5200, but is likely not the best choice for those on a single slow G4 with a terrible graphics card.
The developer of QMplay2 did an amazing job with correctness, but it is understandably heavier than command line players without QMPlay2's excellent interface and features.