[vlc-devel] swscale painfully slow on slow machine

jboileau jboileau at gmail.com
Tue Oct 6 16:33:48 CEST 2009


I have come accross a problem with VLC when it needs to resize a video to
fit the window it needs to play in on some hardware. As a comparaison, I
have done the same test with MPlayer to see if it is a limitation of the
hardware we are using or if different players behave differently.

If the window is the exact same size as the video, no resizing needed, both
players use around 5% of the cpu. But when the window is a bit smaller than
the video it needs to play, forcing resizing, MPLayer still only uses 5% of
the cpu but VLC uses 85% to 95% of the cpu. The swscale plugin seems to be
inneficient in this configuration.

I have tried playing with some of the preferences without any luck. Does
anyone have any ideas of what options I could play with that might help get
the cpu usage down? Is swscale known to be inneficient with some hardware
configurations? Is there an alternative to swscale?

The machine configuration: Celeron 1ghz using Windows XP embedded and a
basic graphics card, the kind that is part of the motherboard. I am trying
to play h264 video 320x240. My tests where done with 'overlay' disabled in
VLC since with overlay enabled I get even poorer results.

PCs with better CPUs and better graphic cards do not exhibit this behaviour.
For example, my dual core laptop with nVidia graphic cards does not give me
significant CPU usage difference as on the above hardware.

Any help would be greatly appreciated.


Jacques Boileau
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