Bug 337622

Videos are downloaded from the interwebz, invert is divx encoded.
Afaik QML uses gstreamer -> can you

   gst-play http://files.kde.org/plasma/kwin/effect-videos/invert.mp4

Please answer the question from comment #1 whether gst-play can play the video.

Konsole says: 
gst-play: command not found

I'm using KDE Neon now. Is it a packaging issue?

Seems to be provided by gstreamer1.0-plugins-base-apps

It still says command not found after installing gstreamer1.0-plugins-base-apps
The binary it gets is called /usr/bin/gst-play-1.0
But when running it:
pascal@pascal-x1:~$ gst-play-1.0 http://files.kde.org/plasma/kwin/effect-videos/invert.mp4
Press 'k' to see a list of keyboard shortcuts.
Now playing http://files.kde.org/plasma/kwin/effect-videos/invert.mp4
ERROR No URI handler implemented for "http". for http://files.kde.org/plasma/kwin/effect-videos/invert.mp4
ERROR debug information: gsturidecodebin.c(1427): gen_source_element (): /GstPlayBin:playbin/GstURIDecodeBin:uridecodebin0
Reached end of play list.

also, the video button in the settings module still doesn't work.

I just downloaded the file and played it with gst-play-1.0 on a debian testing system. Can you try to download it first?

did it, it's missing a codec.
pascal@pascal-x1:~$ wget http://files.kde.org/plasma/kwin/effect-videos/invert.mp4
--2016-08-30 12:13:54--  http://files.kde.org/plasma/kwin/effect-videos/invert.mp4
Resolving files.kde.org (files.kde.org)... 195.135.221.71, 2001:67c:2178:7::71
Connecting to files.kde.org (files.kde.org)|195.135.221.71|:80... connected.
HTTP request sent, awaiting response... 302 Found
Location: http://mirrors.dotsrc.org/kde-applicationdata/plasma/kwin/effect-videos/invert_1.mp4 [following]
--2016-08-30 12:13:54--  http://mirrors.dotsrc.org/kde-applicationdata/plasma/kwin/effect-videos/invert_1.mp4
Resolving mirrors.dotsrc.org (mirrors.dotsrc.org)... 130.225.254.116, 2001:878:346::116
Connecting to mirrors.dotsrc.org (mirrors.dotsrc.org)|130.225.254.116|:80... connected.
HTTP request sent, awaiting response... 200 OK
Length: 5307282 (5,1M) [video/mp4]
Saving to: ‘invert.mp4’

invert.mp4                                                   100%[=============================================================================================================================================>]   5,06M  10,7MB/s    in 0,5s    

2016-08-30 12:13:55 (10,7 MB/s) - ‘invert.mp4’ saved [5307282/5307282]

pascal@pascal-x1:~$ gst-play-1.0 invert.mp4 
Press 'k' to see a list of keyboard shortcuts.
Now playing /home/pascal/invert.mp4
WARNING No decoder available for type 'video/quicktime, variant=(string)iso'.
WARNING debug information: gsturidecodebin.c(939): unknown_type_cb (): /GstPlayBin:playbin/GstURIDecodeBin:uridecodebin0
ERROR Your GStreamer installation is missing a plug-in. for file:///home/pascal/invert.mp4
ERROR debug information: gsturidecodebin.c(1006): no_more_pads_full (): /GstPlayBin:playbin/GstURIDecodeBin:uridecodebin0:
no suitable plugins found:
gstdecodebin2.c(4565): gst_decode_bin_expose (): /GstPlayBin:playbin/GstURIDecodeBin:uridecodebin0/GstDecodeBin:decodebin0:
no suitable plugins found:
Missing decoder: Quicktime (video/quicktime, variant=(string)iso)

Reached end of play list.

Reassigning to neon to have the dependencies updated

https://packaging.neon.kde.org/plasma/kwin.git/commit/?id=72a786183b7c5c710f5d0247430066135b6851be

FTR:
- kwin should assert needed decoders as runtime dependencies via cmake
- qtmm should adhoc install codecs via available api https://gstreamer.freedesktop.org/data/doc/gstreamer/head/gst-plugins-base-libs/html/gst-plugins-base-libs-gstpbutilsinstallplugins.html instead of being useless

When will the fix be available in KDE Neon User edition for verification?