It could be ffdshow.
I had problems with stuttering of the videos in Mala with it.
My videos are Divx.
I uninstalled
ALL the video codecs I had. Then installed the latest xvid (It can decode divx video).
This fixed my problem. If you get black and white video after doing this. You need to run "configure decoder"
and select one of other color settings. Not sure which one it was.
As far as keep aspect ratio - I have that turned off.
All my snapshots and marquee images have been run thru a photoshop droplet and are the same size.
That makes it so I can use image lists in Mala and have drop shadows in the background behind the images.
There may be some videos that are scaled a bit oddly and can cause a green border on one side of the image.
That could probably be fixed by re-capturing the video at a different resolution.
The area where my videos are shown is always black for me. Here is a screenshot of my Mala background.

These videos are the same ones I used in Mamewah. They worked fine there as well.
Bloodwyn