Since version 16.6 the SMPlayer packages are built with Qt 5 by default.

However some users don’t like Qt 5 (for example the file open dialog is different) or there are bugs (for example in some versions of Qt 5 the numeric keypad keys don’t work as accelerators). For that reason now there’s available another PPA for Ubuntu with packages compiled with Qt 4.

https://launchpad.net/~rvm/+archive/ubuntu/smplayer-qt4

To install packages from that PPA, first remove the normal PPA:

sudo add-apt-repository -r ppa:rvm/smplayer

Add the new one:

sudo add-apt-repository ppa:rvm/smplayer-qt4

Update and install:

sudo apt-get update
sudo apt-get install smplayer smplayer-themes smplayer-skins