I am relatively new to video and have been using kdenlive which I find excellent, however I am struggling to produce rendered files with adequate lip sync.

My camera produces .MOV clips 720p 29.97fps (Kodak Zx3) which I can work with in kdenlive, however rendered files have a gradually increasing delay on video of around 1 second in 10 minutes.

Reading the forum I saw a recommendation to first convert the source files to lossless Matroska which I did in 7.8, only to find that the transcoding chopped many frames worth of sound from the end of each clip. I filed a bug. http://www.kdenlive.org/mantis/view.php?id=1962

I have now compiled and installed the latest trunk of kdenlive and tried again. The transcoded Matroska clips are now OK and rendering a project to mpeg4 produces an improvement in sync, but it is still unacceptable (around 1 second in 20 minutes of file).

I am measuring the errors by loading the rendered files back into kdenlive and looking at the thumbs.

I have found a way to correct the error, by transcoding from the rendered mp4 to Matroska using mkvmerge and appling a fractional stretch (i.e. shrink) to the video.
This produces a perfect (sync) .mkv file which I can render back to mp4 in kdenlive.

This last render does not upset the sync, so I can only assume that the errors are introduced by kdenlive when combining the original clips (several hundred in a project) vs. rendering from one clip.

This correction process is very time consuming and messy and I feel there must be a better way.

Can anyone help?

Hi Pete,
Thanks for your input.
I have finally managed to at least work around this problem by cropping 4 frames from the end of each clip. It took a lot of experimentation, but doing this I can now edit 150 clips into a 20 minute video rendered to mp4 in kdenlive with only a 2 frame sync error at the end.
With fewer frames cropped the error increases dramatically. It seems that the software has to make something of a guess about the actual number of frames - and gets it wrong, leaving invalid frames at the end of each clip. These extend the video but not the audio so the audio track moves progressively further ahead of the video at each clip join.
I am trying to convince Dan to make a 4 frame crop standard in kdenlive, as after hacking a build to do just that I can now just throw clips straight onto the timeline and render without any worries.
It's taken over two months to get to the point where I can actually use kdenlive without continually struggling with sync issues.

The indexing feature in avidemux looks interesting - I have tinkered with avidemux, but never noticed that feature. I will take another look.

I was wondering what sort of capture card to look for for doing some VHS conversions, so your musings in that link are much appreciated!
Barry (also UK)