I haven't had sync issues since 2008
I haven't had THAT issue since the KDE 3.5 versions in Ubunty Gutsy and Hardy! Since then, in OS's ranging from Ubuntu Jaunty all the way to Cinnamon over Ubuntu Trusty (14.04), and on machines from Intel Atom to AMD Athlon 64 all the way to AMD FX 8120, I've never had this problem again. Source files have been motion jpegs, AVCHD with H264 streams, even downloaded flv files. The only time I had sync/speed issues were with some H264 streams transferred out of .MTS containers into MP4 containers about a year ago, when doing this from the ffmpeg command line made files something in Kdenlive or MLT didn't like. These had severe speed issues, switching to .flv containers fixed that. Finally, sometime last summer the orignal MTS files from my camera because usable without seek issues getting to a starting point on playback of the timeline, so now I use them directly.
Originally Posted by Mr_Alien_Overlord
The old KDE3.5 versions had to very bad bugs: the sync issues, (which could be worked around by using a 25fps project rate and setting the camera for 25fps) and an ugly tendecy to narrow and pillerbox the files I was importing at that time. In 2008 I didn't know enough about video editing to find a fix for that, but the KDE4 versions of Kdenlive never had that problem anyway. If you haven't used Kdenlive since KDE3.5, try it again, you will be amazed at how far this wonderful program has come.