Scaling and padding clips

I'm not sure where to post this question, so I'm putting it in here. It might be more of an FFMpeg question, but I am using Kdenlive for as many things as I can, and it also uses FFMpeg as a back end for many things.

My system is:
Hardware: Dell Inspiron laptop 1420 N series;
OS: Ubuntu Linux 10.04 LTS
Kdenlive: Version 0.9.2

Let's assume I have a DVD from which I want to rip about 20 minutes of video and convert it to HD 1080p, 25 fps format before editing it further in a Kdenlive project with those settings. I can do it all in FFMpeg, but what is the most efficient way of doing it in Kdenlive? Right now I am stuck in a scaling + padding run with FFMpeg which is going at 2 frames per second (that's right, 2 frames per second!)

First of all, I extracted the desired material from the DVD (which is in NTSC format, aspect ratio is 4:3) and converted it to 25 fps, deinterlaced and resized to 768x576 with a pixel aspect of 1:1 with codec libx264 and "-sameq" quality flag. That took a reasonable amount of time at approx. 10 fps.

Next, I have that input video (called "Ballet.mp4") and this command line in ffmpeg:
ffmpeg -i Ballet.mp4 -s 1440x1080 -vf pad=1920:1080:240:0 -vcodec libx264 -sameq -y Ballet_1080p.mp4

It is working correctly, but it is so SLOW! Can I do this faster in Kdenlive??

I'd edit the original DVD material in kdenlive with a DVD project setting and render to Mpeg2 I Frame as an intermediate, under kdenlive's lossless render profiles, leaving it all interlaced then let your media player do the upsample, upscale and deinterlace at playback or do the rest of the business for anything that really mattered or where I was unsure of playback method, through either Avisynth with QTGMC, or your command line ffmpeg stuff from the mpeg2 I frame intermediate to whatever delivery as last option.