Openshot lags when working with many clips on timeline

[Dmitry Sinyavin]

I have many segments on a timeline in a signle track, probably about a hundred. Every time I change a clip on a timeline somehow, openshot lags for several seconds before playback. Threre're a lot of messages in console during the lag:
[avi @ 0x13f8dd60] sample size (1) != block align (1024)
[avi @ 0x13f8dd60] max_analyze_duration reached
which comes from avformat_find_stream_info() in libavformat, which's called from get_basic_info() in mtl, I haven't made any further research 'cause I'm not a python guy :)
Looks like openshot tries to get stream info for every clip on a track when track contents changes?
Here's a screencast: http://s0me0ne.com/external/openshot.ogv
Note two lags: first one after I drop a clip to timeline and click on a timeline on some point inside a clip, and the second one, after a clip is cut, between pressing of "play" button and actual playback start.
Running on Core i7-2600 @3.4GHz with 12Gb RAM.

$ uname -a
Linux ws 3.2.0-22-generic #35-Ubuntu SMP Tue Apr 3 18:33:15 UTC 2012 x86_64 x86_64 x86_64 GNU/Linux

$ cat /etc/lsb-release
DISTRIB_ID=Ubuntu
DISTRIB_RELEASE=12.04
DISTRIB_CODENAME=precise
DISTRIB_DESCRIPTION="Ubuntu 12.04 LTS"

$ dpkg -l |egrep 'openshot|libav.*5[23]|mlt|melt|python2'
ii libavcodec52 4:0.6.4-0ubuntu0.11.04.1 Libav codec library
ii libavcodec53 4:0.8.1-0ubuntu1 Libav codec library
ii libavdevice53 4:0.8.1-0ubuntu1 Libav device handling library
ii libavformat52 4:0.6.4-0ubuntu0.11.04.1 Libav file format library
ii libavformat53 4:0.8.1-0ubuntu1 Libav file format library
ii libmlt++3 0.7.6+git20120204-2 MLT multimedia framework C++ wrapper (runtime)
ii libmlt-data 0.7.6+git20120204-2 multimedia framework (data)
ii libmlt4 0.7.6+git20120204-2 multimedia framework (runtime)
ii libpython2.7 2.7.3-0ubuntu3 Shared Python runtime library (version 2.7)
ii melt 0.7.6+git20120204-2 command line media player and video editor
ii openshot 1.4.2-1 Create and edit videos and movies
ii openshot-doc 1.4.2-1 Help manual for OpenShot Video Editor
ii python-mlt3 0.7.6+git20120204-2 multimedia framework (python bindings)
ii python2.7 2.7.3-0ubuntu3 Interactive high-level object-oriented language (version 2.7)
ii python2.7-minimal 2.7.3-0ubuntu3 Minimal subset of the Python language (version 2.7)

[Olivier Girard (eolinwen)]

Effectively. And it seems to be just AVI files.
Have you try to update your version of MLT ?
See here how to do this operation : https://answers.launchpad.net/openshot/+faq/1861
Thanks.

[Dmitry Sinyavin (s0me0ne)]

Looks like my libmlt is even newer than on Sunab ppa

mine is libmlt4 0.7.6+git20120204-2

version in the ppa pool is libmlt4_0.7.6-0ubuntu0~sunab~oneiric3_amd64.deb, published 01-Nov-2011

[Andy Finch (fincha)]

Those messages are coming from ffmpeg. After you change a clip, OpenShot recreates the MLT xml. I guess at some point MLT must do something with ffmpeg that creates those messages.

[madpentiste (antoine-messiah)]

I had the same kind of problems (working with many video filess photo files, audio files, titles, image sequences, etc., all totalizing over 1Gb of source material and over half-hour of final video).

The problem disappeared when I put files on several separate, fast-access, USB keys (for example Patriot).
I tried the following configuration:
    - videos on one USB key
   - projects and thumbnails on a second USB key
    - other files (music, pictures/photos, sequence of pictures) on a third USB key

With that configuration, everything worked fast, almost instantly.

The downside is that if you do this in the middle of an ongoing project, you'll have the usual message "The following file(s) no longer exist", in which case you have to change each file property (the path part of the name) to reflect the files new location.