Because of the "white lines bug", I'm using Kdenlive-svn and mlt-git. The white lines are gone, but now I have a problem with rendering my videos.

Rendering the video (for example with "melt example.kdenlive -consumer avformat:example.mp4 real_time=0 f=mp4 acodec=libmp3lame ab=128k ar=44100 vcodec=mpeg4 minrate=0 b=6000k s=1366x768 aspect=%dar mbd=2 trellis=1 mv4=1 subq=7 qmin=10 qcomp=0.6 qdiff=4 qmax=51 pass=2") results in a

Unable to parse option value "%dar": undefined constant or missing (
example.mp4_2pass.log: No such file or directory
[mp4 @ 0x958540]track 1: codec frame size is not set

I also get the last line, when trying to render the video in kdenlive (same setup).

Kubuntu 10.04, 64bit.

Is this a problem with mlt-git or did I compile something wrong or...?

One problem when rendering with melt is "aspect=%dar". You have to replace %dar with the actual display aspect ratio.
Removing the aspect parameter might also work.
And to the main problem:
Do other codecs work?

What should I write in "aspect=" for 16:9? And which videocodec can I try? I don't know the exact phrase and I don't see the documentation for melt.

aspect=@16/9

and to get a list of video codecs:

ffmpeg -formats or -codecs depending on your ffmpeg version.

Thanks for your help, but still gives me this "[mp4 @ 0x958540]track 1: codec frame size is not set" problem. At least, I got kdenlive working in Arch Linux (in a good quality for me). Maybe something with my Kubuntu 10.04 install is wrong.