Currently videoscale only supports Nearest Neighbour as scaling method. 
 
Nearest Neighbour is fast and works pretty well for scaling up, but is just 
not really usable for down-scaling video images. The resulting picture is very 
blocky with 'stair-case' effects that are very easy to notice at almost all 
(picture object) edges. 
 
It would be great if GStreamer would implement scaling methods that produce 
reasonable results for downscaling as well. 
 
gdkpixbufscale is not really an alternative, as it only accepts rgb input, and 
the colorspace conversion seems to be very expensive compared to the actual 
scaling (from a couple of quick tests I made using gst-launch and 
videotestsrc). 
 
Cheers 
 -Tim