UI becomes sluggish/unresponive with large animated title

[Burt Bicksler]

I've encountered a problem with V 2.3.3 and large animated title clips (and I suspect and clip containing a large number of .png still frames.

The animated title I tested with had over 2000 individual .png stills in it.

Architecture (64 bits or 32 bits) : 64 bits
Operating System & version: Linux Mint 17.1
Ram: 8 GBytes
HardDrive: about 500 GBytes free
AMD Radeon graphics card with proprietary driver installed
Installation Method : Runfine downloaded from Openshot.org
Version of Openshot installed : 2.3.3
BZR Revision used (if any) :
MLT/melt version: 0.9.0
avconv version: 9.20-6:9.20-0ubuntu0.14.04.1
FFmpeg (i.e.libavcodec) version : libavcodec-ffmpeg56
FFmpeg installation : None found in path, avconv is present

Imported a short video from my phone. Had the phone in wrong orientation so video was rotated.
Rotated video in time line 90 degrees. That was easy.

Then generated an animated title (Space Movie).
Dragged that title clip into the time line and then moved it ahead of my first clip.
At that point the UI became unresponsive, and would not repaint if resized. After maybe a minute or two the UI became responsive again.

No crashes. But if I move the clip(s) or transition in the time line the UI becomes unresponsive again.

Once the UI is responsive again the video plays in OpenShot, and I was able to export it just fine.
But if I move the cursor in the time line and then click play it takes up to a minute before the video starts to play again from the new location. It plays fine with no stuttering, etc.

It is very repeatable, if I move the cursor again, the problem repeats, and usually the cursor will only move a fairly shot distance until I release the left mouse button and then I can click the cursor again and continue dragging it.

It appears that if I drag the cursor where I want it and then wait for several seconds, up to a minute or so, that I can click play and it starts playing from the new location.

Note that the total video time is about 2 minutes and 40 seconds on the time line.

How to reproduce:
1 - Generate the Space Movie animated title (I just used all the defaults for my test).
2 - Have a short mp4 clip in the project, may be optional I didn't try without it.
3 - Add the Space Movie title in front of the short mp4 clip.
4 - Play the video and note that it works fine in the preview window
5 - Render the video and note that it renders and then plays fine in an external player
6 - Try moving the cursor/playhead around in the track. Note that the preview window does not update for a long time. Also note that if you position the play head back say 50 seconds and press play that the video does NOT start playing for a long time, in my case nearly a minute. Also note that if you resize the OpenShot application that the window doesn't repaint and in some cases you also will get a pop up about a script has stopped working do you want to terminate.

Unless this is something specific to my configuration this appears to be a buglet.

Note that I have not had this problem with Kdenlive with even larger clips comprised of individual .png files running on the same machine.

Shorter animated titles, tested up to about 200 frames, do NOT have this problem, everything is still responsive with those shorter animated titles.

Also, I was able to work around the issue by just bringing the Space Movie title into the time line and rendering it to an mp4. Then I brought that rendered title mp4 into my project and everything was perfectly fine, so it is only the originally generated longer animated title clips made up of individual .png image sequences that cause the issue.

[Burt Bicksler (burt-e)]

I meant to say at the start of the description that the UI becomes unresponsive AFTER I move the cursor / read head around on the time line or move the clips on the time line, not just on loading the title.