Dolphin does not show thumbnails

I have changed my Unity default file manager to Dolphin.

Problem: video thumbnails don't show up anymore.
In Nautilus the thumbnails are shown correctly.

How to make Dolphin show thumbnails?

Solution 1:

Thumbnailer

To show thumbnails the Dolphin will need the thumbnail plug in.

Video thumbnailers for the Dolphin:

:~$ apt-cache show ffmpegthumbs
Package: ffmpegthumbs
Priority: optional
Section: universe/kde
...
Description: video thumbnail generator using ffmpeg
 FFMpegThumbs is a video thumbnail generator for KDE file managers
 like Dolphin and Konqueror.  It enables them to show preview images
 of video files using FFMpeg.
 .
 This package is part of the KDE multimedia module.

Homepage: http://www.kde.org/

.

:~$ apt-cache show mplayerthumbs
Package: mplayerthumbs
Priority: optional
Section: universe/kde
...
Description: video thumbnail generator using mplayer
 MPlayerThumbs is a video thumbnail generator for KDE file managers
 like Dolphin and Konqueror.  It enables them to show preview images
 of video files using MPlayer.
 .
 This package is part of the KDE multimedia module.

Homepage: http://www.kde.org/

.

:~$ apt-cache show kffmpegthumbnailer
Package: kffmpegthumbnailer
Priority: extra
Section: universe/kde
...
Description: video thumbnailer for KDE
 kffmpegthumbnailer is a video thumbnailer based on ffmpegthumbnailer.
 The thumbnailer uses ffmpeg to decode frames from the video files.

Homepage: http://www.kde-apps.org/content/show.php/kffmpegthumbnailer?content=117562

Settings

To use the thumbnail you need to enable the thumbnailer from the Dolphin settings.

Solution 2:

In a terminal run

sudo apt install ffmpegthumbs mplayerthumbs kffmpegthumbnailer

then... change in dolphin settings as says in user26687's answer... works for me kubuntu 14.04lts in laptop n4010 dell

Solution 3:

1. Install the following packages: ffmpegthumbs mplayerthumbs kffmpegthumbnailer kio-extras
2. Restart Dolphin
3. Settings > Configure Dolphin > General > Behavior > View > Use common properties for all folders, OK
4. Press the "Preview" button

Solution 4:

Now in Ubuntu 15.10 I needed another package for thumbnails to show:

sudo apt-get install kio-extras