Netbook out of sync on audio

[steeerpike]

I have an Asus netbook with an Atom processor (Win 7) and video playback on a mkv file under vlc shows big black blocks as the cpu maxes out. Under smplayer I have smooth playing but the audio file is out of sync with the video. Sometimes dragging the progress bar fixes it temporarily but again the wrong person is talking.
I love smplayer for a mp4 but this problem means my little netbook can't play some videos well - any suggestions?

[rvm]

There are several things you can try:

In preferences -> performance, disable the loop filter. This reduces the CPU usage but the image quality will be worse.
You can also try to check the option "allow frame drop".

In preferences -> general -> video you can try to set the video output to directx.