Using "Melt" to render the preview?

Hello everyone!
I've been using Kdenlive for a while and it is clearly the best video editor (the easiest + most powerful).
Thank you very much :-)

So here is my question:
I have seen in the System Monitor that the process Kdenlive, when previewing, uses a lot of CPU
And when rendering, the process that uses lots of cpu is "Melt"

The thing is that, when previewing, kdenlive often crashes, but it never does when rendering; why?

Thanks again!

PD: Other thing, it must have already been asked but what about a pre-rendering like in other video editing software? It is slower but more useful when having lots of video.

Melt is the command line tool for MLT. Kdenlive uses MLT for the preview - it is the engine of Kdenlive, but Kdenlive is using the MLT API and not launching melt as a separate process. Now, render does launch melt to let it run in the background.

Ok thanks for the explanation ;-)

But then I don't understand why it freezes when it generates the previews and not when rendering in the background... I suppose it is because it overloads melt.

Sorry because i'm not sure how mlt works so I'm probably asking weird questions.

Thanks again