I'm running Kdenlive (0.7.7.1) on my new Ubuntu Lucid (10.04) install. I'm running Gnome, not KDE. Kdenlive seems to run fine (although I'm having a problem with transitions), but I can't render anything. My input file is a 1440x1080p MP4 file.

I've tried a bunch of different "render to file" options, but every one gives me the error message "codec frame size is not set." I've Googled all morning but haven't found an answer.

Can anyone help? I REALLY don't want to go back to Windows for my video editing!

Usually this is because you are trying to use a codec that is no longer available.
From the menu choose Settings > Run Config Wizard
Now see which render profiles are available.

Here are related threads/bugs:
http://ubuntuforums.org/showthread.php?t=1443653
http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=599490

You can try installing the libavformat-extra package:
http://packages.ubuntu.com/lucid/libavformat-extra-52

If you do, re-run the Kdenlive Config Wizard.

Thanks, that helped some. Now I can render to most formats, but h264 now has red Xes next to all the options.

this used to work just fine and all of a sudden something made me not be able to render to h264. Is it FFMPEG? I have installed the libavformat-extra-52 already. This stinks, I was just rendering to h264 a week ago and now I can't. Any help anyone?

http://www.mltframework.org/twiki/bin/view/MLT/BuildScripts

Apparently FFMPEG had to be updated due to some security flaw and medibuntu's version of libavformat-extras-52 was older then the ones in Ubuntu so it was using the newer versions from Ubuntu's repo instead of medibuntu's repo. Once I updated my lucid medibuntu repo to point to "lucid-staging" instead of only "lucid" it now works again being able to encode to mp4 (h264/aac). I had to update it located in

/etc/apt/sources.list.d/no-medibuntu.list

not sure what that's all about but I am just glad I can encode my youtube clips to .mp4 again.

the bug is here for anyone curious. https://bugs.launchpad.net/ubuntu/+source/ffmpeg/+bug/738134