Greetings folks!

It used to be possible to use a PNG-file with an alpha-channel as a logo-overlay for a video-clip. Under the versions of kdenlive/libmlt/libavcodecs/libavformats coming with Ubuntu 11.10 (Oneiric Ocelot) this stopped working.

See http://macslow.net/images/kdenlive-composite-attempt.jpg for the way I arranged the scene.

The installed versions of all the related packages:

kdenlive 0.8-4
libmlt4 0.7.2+git20110530-1build1
libavcodec-extra-52 4:0.6.2-1ubuntu2
libavcodec-extra-53 4:0.7.1.0ubuntu2
libavformat-extra-52 4:0.6.2-1ubuntu2
libavformat-extra-53 4:0.7.1.0ubuntu2

Can anybody tell my why this standard operation stopped working?

Thanks in advance!

Best regards...

MacSlow

I do not know for sure as I do not have those versions running here, but I am going to make an educated guess. If you have the gtk2 plugin to MLT (most people do), then it uses gdk-pixbuf first to try to load a PNG with alpha. It might be that in new version of GTK+ something changed and is breaking how the alpha channel is copied into MLT. You can (re)move the plugin temporarily (/usr/lib/mlt/libmltgtk2.so) to see if forcing it to use the QImage loader works any better. Also, you might try running with LC_NUMERIC=C or something with period for decimal point. Lastly, it could be that you are using a git snapshot of MLT, and it was made at a bad time with little testing for how well it works with release version of Kdenlive.

Getting closer, sort of...

Removing /usr/lib/mlt/libmltgtk2.so did not have any effect. So I reverted that change again. But starting kdenlive from a terminal with "LC_NUMERIC=C kdenlive" did have an effect, resulting in the Composite-transition to work again as expected. But only in the preview. When rendering out the animation it only takes a second and the resulting video is only 259 bytes long.

Any idea how to explain that?

Oh, I selected "H.264 6000k 2-pass", which usually works.

EDIT: Hm... only using "single pass" seems to work.

Best regards...

MacSlow

There have been long-standing LC_NUMERIC-related bugs with respect to numeric strings in XML project, etc. These were fixed over the course of the past couple of months. So, it looks like you either hit that bug or a bad combination of mlt/kdenlive in the midst of fixing them. I do not know the full status of Kdenlive with respect to those fixes since I work primarily on MLT. Now, for the rendering, things have been complicated with the split of ffmpeg and libav and their new versions combined with x264 and its pace of recent changes. Tough times indeed. Thanks for the feedback.