Crop, Scale and Tilt effect causing image blur?

[Harald Albrecht]

Hi,

I have source footage (recorded from a Raspberry Pi Touch LCD btw) which 
I need to crop before compositing it in the timeline with other clips. 
So I'm using a dedicated timeline track and apply a "crop, scale and 
tilt" effect to this track. I do not scale, leaving both Scale X and 
Scale Y at 50. I'm just cropping.

Unfortunately, the resulting cropped frames are slightly blurred. I can 
see this by comparing the timeline result with the original footage.

Can someone help with this? Is there some unwanted rescaling going on 
behind the scenes inside MLT that is causing such blur?

I've actually seen this in other projects too, but then worked around it 
by using a sharpening effect. But this really isn't the right thing to 
do I suppose...

Best regards,
Harald