Hi klaviaturist,

Connect each player's SIGNAL to the one seekslider SLOT.
Nothing is stopping you to have multiple signals connected to one slot.

Something like this:
Qt Code:
  1. connect( player_1, SIGNAL(progress(int)), seekslider, SLOT(setProgress(int)) );
  2. connect( player_2, SIGNAL(progress(int)), seekslider, SLOT(setProgress(int)) );
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Regards,
Wladek