Hello,

I am usually editing video projects in 1920x1080 50 fps. No wonder I like using use proxy clips.
Last day I did some extensive editing and in the end I found Kdenlive utilizing proxy clips completely ruined my work.

The main and most problematic part of the job was taking one clip and cutting it into several parts. I modified crop starts and crop ends of the parts a put them in line.
So, basically, I cut out some parts of the original clip. I needed exact frame accuracy where I was "joining" the cropped parts again.
Next, I split audio from the parts and again cropped its starts and ends. I needed only several 1 second parts of audio.

Everything was perfect until I rendered the project. When I did, I found that the cut clips with cropped starts/ends are shifted in the rendered video.
My video cuts/joins moved by, at least, several frames. Also the audio cuts moved by as much as half a second. It is still aligned to the video (no AV sync problem),
but it was cut at different points than I intended to. In fact, I do not know if there is a difference in video position, audio position or both of them.

The problem is in the difference and time position inaccuracy between original and proxy clip. When I edit the proxy version, everything is exactly how I cut it.
If I render file using the proxy clips, it is perfect. But when I try to switch proxy clips off or render using original HD clip, my cuts does not match the points
where I edited them using proxy clips. Both is affected. Rendered video and clips in Kdenlive when proxy clips are switched off.
When I switch proxy clips back on it is good again. I cut using proxy clips so they are exact. But I am not able to edit and/or render the project in original resolution.

There must be a problem with the proxy clips and their position/frame accuracy to the original clip. I have lost a lot of work and it looks like I cannot recover it.
Also, with lost confidence in proxy clips, I have to rework it all in full resolution. That looks almost impossible.

I would like to ask you if I have missed something or if this is a known bug/behavior.

I am using Kdenlive 0.9.6 on recent Ubuntu.

Thank you.

Hello and welcome,

1. I had this problem quite some time ago with proxies and I am sure it was fixed, but you could check.

With proxies on, adjust the timeline so you can see a clips thumbs or just one if you can't see both. Choose a clip with movement if you can. From the Project Tree set yourself up ready to turn off the Proxy for that clip, but as you click watch carefully the clips thumb in the timeline. Hopefully there should be no movement whatsoever.
Hope that made some sense

2. Did you crop etc using the clip's duration box? I have always had problems with that in the past so I don't use it.

Even using Proxies I get frame accuracy by using two (or more) timelines. The cut clips are placed one up, one down, one up and so on. Using the mouse wheel in the Project Monitor I can frame step through the lap-over or join to check accuracy and adjust accordingly, even one frame at a time if needed.

If by any strange chance you understood any of that, try it then select a short zone of a few seconds or so over the join and render that.

Good luck.

Thank you for your reply.

1. The thumbnails do not jump right on allowing/disabling proxy clips but they stop reflecting the monitor window. They do not get updated to the shifted reality until I play about 2 seconds. Then, they move to reflect real frames. I cannot see it when they are moving while playing. The shift is as big as 00:00:19:23 -> 00:00:20:09 (35 frames for 50p video).

2. No, this time I cropped only by dragging the ends of the clips.

The cut clips stay in the positions where I placed them on the time axis. Their content is what changes. Since they are cropped from both sides, they have space to shift. They float that 35 frames left or right when real or proxy clips are used.

Where can I report a bug? This renders proxy clips pretty unusable. And Kdenlive is almost unusable as whole when editing fullres.

Luckily I have never encountered this problem. Is this problem only occuring in one project or all your projects?

Hmm ... what kind of proxy clips (profile) do you use? I wonder if the effect you're seeing may be related to searching inside video streams ... which I've learned the hard way through the speed effect may not working well for certain profiles.

I have no idea. I haven't done many projects in Kdenlive and only this one requires real frame accuracy.
The other projects are not affected or I did not noticed it.

In 0.9.6, there was only one preset for proxy clips. It is called "Normal MPEG" and it comes with these parameters:
-f mpegts -acodec libmp3lame -ac 2 -ab 128k -ar 48000 -vcodec mpeg2video -g 5 -deinterlace -s 480x270 -vb 400k

Since I am not using that low-end PC and I appreciated the quality increase I modified it to:
-f mpegts -acodec libmp3lame -ac 2 -ab 128k -ar 48000 -vcodec mpeg2video -g 5 -deinterlace -s 640x360 -vb 1000k

This project utilizes one reversed clip and also speed effect (slow motion).
Anyway, the speed effect is used near the end of the project while it is shifted (almost?) from the start.

I am pretty clueless. Experimenting with this requires a lot of work and editing 1920x1080 50p is no way to go.

I am still analyzing the problem and I have found that where I (using proxy clips) split audio track, it also A/V desynced.
All the work I have done on the project is definitely gone.

Video is shifted exactly by 36 frames. The proxy version is delayed. The same difference at the start and at the end of the clip.
It looks like only multiple times cut clip with split audio track and some effects is affected. All "subclips" cut from it, all by 36 frames.
Even the "subclips" without any effects.

Looks like the problem is elsewhere but still Kdenlive related. I will look into it more deeply and keep you updated.

Meanwhile I found a little bug. When you create a reversed clip with proxy clips on, a .mlt clip is generated. It also got proxied version and the clip icon is marked "P".
When you turn off proxy clips for the whole project then, all clips revert but the .mlt one. It keeps "P" symbol and still goes from proxy. You also cannot switch it off directly.
You have to turn proxy clips back on to enable the item in the clip menu, turn proxy clip off for the .mlt clip, then finally turn proxy clips off again for the project.

Are the Kdenlive devs reading this or should I post a bug report somewhere?