Is there some way to get a crisp speed effect?

When I use the speed effect to speed up a video it introduces strong artifacts. Even unmoving text on unmoving background becomes blurred.
I think this is caused by some interpolation. Can I turn it off? So that the speed up is achieved by dropping frames. I don't mind if I don't mind if I can only get speed up by whole number factors.

The source video is lossless h264, 10fps. I want to speed up by 12x and encode to 30fps, also lossless h264. This should be possible using only frame dropping. I am using kdenlive 0.8 with mlt 0.7.2.
I will try to do this directly with ffmpeg, but I would prefer a solution which works inside kdenlive.

btw. what does the stroboscope option do exactly?

The speed effect does use frame-dropping and duplication without temporal interpolation. I reproduced the problem, and it seems there is a bug that I will try to fix.